GB1575603A - Refractory structures for outlet valves for metallurgical vessels - Google Patents

Description

(54) REFRACTORY STRUCTURES FOR OUTLET VALVES FOR METALLURGICAL VESSELS (71) We, DIDIER-WERKE AG., a company organised under the laws of the Federal Republic of Germany, of Lessingstrasse 16, 62 Wiesbaden, 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 invention relates to refractory bodies and finds particular use as wearing parts for use in the outlets of metallurgical vessels such as casting ladles and tundishes and as refractory structures for use in outlet control devices for such vessels and in particular sliding gate nozzle apparatus.

The invention is described with particular reference to the casting of steel but the refractory wearing parts according to the invention are also applicable to the casting of other metals which cause considerable wear because of their high melting point or their corrosive nature.

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 frame 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.

Movement of the movable plate can be rotatory though a straight sliding motion is preferred.

One form of such apparatus has a fixed upper plate and a movable lower plate. Such apparatus will be referred to herein as a two plate sliding gate nozzle apparatus. The movable plate is preferably mounted for movement in a metal casing, and may incorporate an outlet nozzle or cooperate with one which is also movably mounted in the metal casing.

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 nozzle apparatus.

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.

Refractory wearing parts of the described kind are exposed in use to widely varying thermal stresses. On the one hand such refractory wearing parts are exposed during the pour to very high temperatures at which metals have a major corrosive and erosive action on refractory materials. On the other hand such refractory wearing parts are exposed at the start of the pour to an unusually severe and sudden thermal shock which gives rise to correspondingly high mechanical stresses due to differential thermal expansion. For both these reasons the service life of known refractory wearing parts of the kind contemplated is short. For example, on average a sliding plate requires replacement after only two pours, representing, for example, a total casting time of only two hours.

According to the present invention a refractory structure, which for example may be used as a fixed or sliding plate for a sliding gate nozzle or as a sleeve or nozzle brick for the outlet from a metallurgical vessel, incorporates an insert at least defining at least one discharge passage for molten metal passing through the refractory structure, the refractory structure comprising body of refractory concrete made from a settable composition comprising refractory aggregate, cement and water moulded to shape around the insert and allowed to set whereby the insert is embedded in the refractory concrete, the insert being of a material having better wear resistance than the refractory concrete.

Refractory structures according to the invention may be produced by pouring a refractory concrete into an appropriate mould, the means defining the discharge passage being disposed in the desired position inside the mould before the concrete is poured.

Thus a process for producing a refractory structure in accordance with the invention comprises providing a mould defining the external shape required for the structure, locating in the mould the insert defining the discharge passage, pouring a cold curing, cold setting refractory concrete composition into the mould around' the insert, optionally compacting the concrete, levelling the concrete in the mould, allowing it to set and removing it from the mould before or after allowing it to cure, and drying the concrete.

According to a preferred form of the invention in sliding gate nozzle apparatus adapted for use with metallurgical vessels comprising at least one fixed and one movable plate, each plate having a discharge passage for molten metal, at least the sliding plate comprises a refractory structure incorporating at least one insert at least defining at least one discharge passage, the refractory structure comprising a cast body of refractory concrete inaterial in which the insert is embedded, the insert being of a material having better wear resistance than the refractory concrete.

The invention may be put into practice in various ways and one specific embodiment will be described by way of example to illustrate the invention with reference to the accompanying drawings, in which- :- Figure 1 is a diagrammatic cross sectional view of an embodiment of a middle plate of a 3-plate sliding gate nozzle apparatus containing a highly refractory insert embedded therein and defining the discharge passage of the plate in accordance with the present invention and Figure 2 is a plan view of the plate shown in Figure 1.

Examples of refractory concretes are hereunder given, such as may be used for making the refractory structures described below.

Example 1 80% by weight of an aggregate containing 40% by weight of Awl203 and having a particle size from 0 to 5 mm are mixed with 20% by weight of a fused alumina cement having a content of 40% by weight of Awl203, 12 litres of water being added in respect of each 100kg of the dry mix.

For the production of a refractory structure this mix is poured into a mould and compacted by vibration should this be desirable. After having sufficiently set the concrete is taken out of the mould, stored to cure and dried.

Example 2 80% by weight of Guyana bauxite containing 88% by weight of Awl203, particle size 0 to 5mm was mixed with 20% by weight of alumina cement containing 70% by weight of Awl203 and 10 litres of water per 100 kg of dry mix. This mix is further processed as described in Example 1.

However, if the refractory structures are in the form of plates to be used for casting steels having melting points above 1500"C which are cast at temperatures 50"C to 60"C above their melting points, the conditions which the plates have to withstand are very much more severe and in order to ensure a more reliable service special compositions must be used.

These conditions consist in a 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 having a temperature of only 200"C to 300"C.

For such very severe conditions it is preferred to use refractory concretes containing from 5 to 8% by weight of an alumina cement, 2-5 td 4% by weight of pulverent refractory material (having a particle size of less than 50 microns and preferably less than 1 micron) such as kaolin or bentonite, micronised silica, micronised alumina, micronised magnesia, micronised chromite or micronised fosterite, 0 01 to 0.30/ by weight of an agent effective to increase the flowability of the composition comprising an alkali metal phosphate, alkali metal polyphosphate, alkali metal carbonate, alkali metal carboxylate or alkali metal humate and from 87 7 to 92/ by weight of at least one refractory aggregate, desirably having a particle size not exceeding 30 mm, and desirably all of which pass a 10 mm mesh and about 25% of which pass an 0 5 mm mesh screen. The refractory aggregate may consist of calcined refractory clay, bauxite, cyanite, sillimanite, andalusite, corundum, tabular alumina, silicon carbide, magnesia, chromite or zircon or mixtures thereof.

An example of such a concrete is given below: Example 3 87-8 to 92% by weight of tabular alumina, particle size 0-6 mm are mixed with 5 to 8% by weight of alumina cement containing about 80% by weight of Al203, 2.5/ by weight of micronised alumina and 0 01 to 0.3/ by weight of alkali metal polyphosphate. 5 litres of water are added per 100 kg of dry mix. The mix is poured into the mould and can be compacted by vibration.

Figures 1 and 2 illustrate a sliding or middle plate 112 of refractory concrete in accordance with the present invention of a 3plate sliding gate nozzle apparatus having a more refractory insert defining the discharge passage embedded in the refractory concrete.

The plate also has a gas-permeable insert 156 which may be a porous body consisting of a coarse-grained mass of corundum or mullite sintered with a small quantity of a cementing agent and exhibiting a gas-permeability of at least 100 nanoperms.

The principal component of the sliding plate 112 is a pressed or cast body 200 containing a rectangular central window 201. In view of the relatively short duration of a pour (from the time of filling to the time of completely discharging the vessel) this body is heated to only a relatively low temperature, e.g. between 400 and 500"C (when casting steel which heats up the walls of the discharge passage to more than 1500"C) For this reason it is not absolutely necessary to make the body 200 of a refractory material.

More important is the choice of a material that is dimensionally particularly stable and insensitive to temperature shock of the described kind, so that this body 200 can serve as a durable frame for the actual gating portion of the sliding plate 112.

The window 201 contains a member 202 which is of the same thickness as the body 200, but which has a slight clearance in the window 210 to facilitate replacement.

The member 202 has chamfered edges 203 and a cast-in cylindrical sleeve 205 which defines the discharge passage 106 for the metal through the sliding plate. This sleeve may be produced by pressing and firing or by casting a highly refractory mass to produce a refractory insert having a better wear resistance than that of the cast refractory concrete of the member 202. Without significantly increasing the cost of a sliding plate the sleeve may consist of a material of the highest quality, such as zircon, which can be standardised for size and shape and which will constitute only a small part of the entire volume of the plate. When the member 205 is used in accordance with the invention the member 202 may be made of a lower quality refractory concrete, such as that described in Examples 1 and 2 above, than would be the case when the member 205 is not used; in that case a concrete as specified above in Example 3 would have to be used.

The member 202 contains the gas-permeable insert 156 embedded therein supported by a metal plate 182 which has an opening 188 communicating with an opening 189 at one end of a metal tube 180 of which the other end opens into a distributing chamber 208 at the bottom of the gas-permeable insert 156.

The gas-permeable insert 156, the tube 180 and the metal plate 182 are assembled and cemented or otherwise joined together, as indicated at 209, before the refractory concrete is poured and the member 205 is also located in the mould before the concrete is poured.

A duct for a working fluid and the location of the gas permeable insert in the cast body forms part of the subject matter of our copending application No. 7926486 Serial No.

1575602 (Case 2827 Div. 1) and attention is directed to it.

The incorporation of a metal reinforcement in the cast body forms the subject matter of our copending application No.

2514/76 Serial No. 1575601.

Both the above mentioned applications include the drawings of the present application. Attention is directed to the claims of the above mentioned applications.

WHAT WE CLAIM IS: 1. A refractory structure incorporating an insert at least defining at least one discharge passage for molten metal passing through the refractory structure, the refractory structure comprising a body of refractory concrete made from a settable composition comprising refractory aggregate, cement and water moulded to shape around the insert and allowed to set whereby the insert is embedded in the refractory concrete, the insert being of a material having better wear resistance than the refractory concrete.

2. A process for making a structure as claimed in Claim 1 which comprises providing a mould defining the external shape required for the structure, locating in the mould the insert defining the discharge passage, pouring a cold curing, cold setting refractory concrete composition into the mould around the insert, levelling the concrete in the mould, allowing it to set and removing it from the mould before or after allowing it to cure, and drying the concrete.

3. A refractory structure as claimed in Claim 1 whenever made by a process as claimed in Claim 2.

4. Sliding gate nozzle apparatus adapted for use with metallurgical vessels comprising at least one fixed and one movable plate, each plate having a discharge passage for molten metal, at least the sliding plate comprising a refractory structure incorporating at least one insert at least defining at least one discharge passage, the refractory structure comprising a body of refractory concrete made from a settable composition comprising refractory aggregate, cement and water moulded to shape around the insert and allowed to set whereby the insert is embedded in the refractory concrete, the insert being of a material having better wear resistance than the refractory concrete.

5. Sliding gate nozzle apparatus as claimed in Claim 4 in which the movable plate comprises a refractory structure which is made by the method claimed in Claim 2.

6. A refractory structure as claimed in Claim 1 and substantially as specifically

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

Claims (7)

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

   The plate also has a gas-permeable insert 156 which may be a porous body consisting of a coarse-grained mass of corundum or mullite sintered with a small quantity of a cementing agent and exhibiting a gas-permeability of at least 100 nanoperms.

   The principal component of the sliding plate 112 is a pressed or cast body 200 containing a rectangular central window 201. In view of the relatively short duration of a pour (from the time of filling to the time of completely discharging the vessel) this body is heated to only a relatively low temperature, e.g. between 400 and 500"C (when casting steel which heats up the walls of the discharge passage to more than 1500"C) For this reason it is not absolutely necessary to make the body 200 of a refractory material.

   More important is the choice of a material that is dimensionally particularly stable and insensitive to temperature shock of the described kind, so that this body 200 can serve as a durable frame for the actual gating portion of the sliding plate 112.

   The window 201 contains a member 202 which is of the same thickness as the body 200, but which has a slight clearance in the window 210 to facilitate replacement.

   The member 202 has chamfered edges 203 and a cast-in cylindrical sleeve 205 which defines the discharge passage 106 for the metal through the sliding plate. This sleeve may be produced by pressing and firing or by casting a highly refractory mass to produce a refractory insert having a better wear resistance than that of the cast refractory concrete of the member 202. Without significantly increasing the cost of a sliding plate the sleeve may consist of a material of the highest quality, such as zircon, which can be standardised for size and shape and which will constitute only a small part of the entire volume of the plate. When the member 205 is used in accordance with the invention the member 202 may be made of a lower quality refractory concrete, such as that described in Examples 1 and 2 above, than would be the case when the member 205 is not used; in that case a concrete as specified above in Example 3 would have to be used.

   The member 202 contains the gas-permeable insert 156 embedded therein supported by a metal plate 182 which has an opening 188 communicating with an opening 189 at one end of a metal tube 180 of which the other end opens into a distributing chamber 208 at the bottom of the gas-permeable insert 156.

   The gas-permeable insert 156, the tube 180 and the metal plate 182 are assembled and cemented or otherwise joined together, as indicated at 209, before the refractory concrete is poured and the member 205 is also located in the mould before the concrete is poured.

   A duct for a working fluid and the location of the gas permeable insert in the cast body forms part of the subject matter of our copending application No. 7926486 Serial No.

   1575602 (Case 2827 Div. 1) and attention is directed to it.

   The incorporation of a metal reinforcement in the cast body forms the subject matter of our copending application No.

   2514/76 Serial No. 1575601.

   Both the above mentioned applications include the drawings of the present application. Attention is directed to the claims of the above mentioned applications.

   WHAT WE CLAIM IS: 1. A refractory structure incorporating an insert at least defining at least one discharge passage for molten metal passing through the refractory structure, the refractory structure comprising a body of refractory concrete made from a settable composition comprising refractory aggregate, cement and water moulded to shape around the insert and allowed to set whereby the insert is embedded in the refractory concrete, the insert being of a material having better wear resistance than the refractory concrete.
2. 2. A process for making a structure as claimed in Claim 1 which comprises providing a mould defining the external shape required for the structure, locating in the mould the insert defining the discharge passage, pouring a cold curing, cold setting refractory concrete composition into the mould around the insert, levelling the concrete in the mould, allowing it to set and removing it from the mould before or after allowing it to cure, and drying the concrete.
3. 3. A refractory structure as claimed in Claim 1 whenever made by a process as claimed in Claim 2.
4. 4. Sliding gate nozzle apparatus adapted for use with metallurgical vessels comprising at least one fixed and one movable plate, each plate having a discharge passage for molten metal, at least the sliding plate comprising a refractory structure incorporating at least one insert at least defining at least one discharge passage, the refractory structure comprising a body of refractory concrete made from a settable composition comprising refractory aggregate, cement and water moulded to shape around the insert and allowed to set whereby the insert is embedded in the refractory concrete, the insert being of a material having better wear resistance than the refractory concrete.
5. 5. Sliding gate nozzle apparatus as claimed in Claim 4 in which the movable plate comprises a refractory structure which is made by the method claimed in Claim 2.
6. 6. A refractory structure as claimed in Claim 1 and substantially as specifically

   described herein with reference to the accompanying drawings.
7. 7. A sliding gate valve incorporating a refractory structure as claimed in Claim 5.