AU2007249057A1

AU2007249057A1 - Regulation method for throughflow and bottom nozzle of a metallurgical vessel

Info

Publication number: AU2007249057A1
Application number: AU2007249057A
Authority: AU
Inventors: Martin Kendall
Original assignee: Heraeus Electro Nite International NV
Current assignee: RHI AG
Priority date: 2004-11-26
Filing date: 2007-12-17
Publication date: 2008-01-10
Anticipated expiration: 2025-11-17
Also published as: AU2007249057B2

Description

S&F Ref: 742292D1

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address of Applicant Actual Inventor(s): Address for Service: Invention Title: Heraeus Electro-Nite International of Centrum Zuid 1105, 3530, Houthalen, Belgium Martin Kendall Spruson Ferguson St Martins Tower Level 31 Market Street Sydney NSW 2000 (CCN 3710000177) Regulation method for throughflow and bottom nozzle of a metallurgical vessel The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845c(1065236 1) SRegulation Method for Throughflow and Bottom Nozzle of a Metallurgical Vessel The invention relates to a method for regulating the throughflow through a bottom nozzle of a metallurgical vessel. Furthermore the invention relates to a bottom nozzle of a metallurgical vessel.

In particular, in steel melting the liquid metal is cast from a distributor, for example in a S continuous casting plant. It flows through a bottom nozzle arranged in the floor of the distributor housing. Adherence of material to the wall of the bottom nozzle during throughflow is disadvantageous. The cross section of the aperture is thereby decreased, so that the flow properties are disadvantageously affected. To prevent the adherence of material to the wall, an inert gas such as argon is often introduced into the throughflow aperture. However, excessive amounts of gas negatively affect the steel quality, for example by the formation of cavities in the steel which lead to surface defects when the steel is rolled.

A material for a bottom nozzle is described, for example, in WO 2004/035249 Al. A bottom nozzle within a metallurgical vessel is disclosed in KR 2003-0017154 A or in US 2003/0116893 Al. In the latter publication, the use of inert gas is shown, with the aim of reducing the adherence of material to the inner wall of the bottom nozzle (so-called clogging); this is similarly described in JP 2187239. A mechanism with a gas supply regulation is known in detail from WO 01/56725 Al. Nitrogen is supplied according to the Japanese publication JP 8290250.

Jp 3193250 discloses a method for observing the adherence or clogging of material with the aid of numerous temperature sensors arranged one behind the other along the bottom nozzle. The introduction of inert gas into the interior of the bottom nozzle is further known from, among others, JP2002210545, JP61206559, JP 58061954, and JP 7290422. It is furthermore known from a few of these publications, in addition to introduction of inert gas, to prevent the access of oxygen as far as possible by the use of housings around a portion of the bottom nozzle. An excess pressure of inert gas is partially produced within such a housing, for example in JP 8290250. A housing around a valve of the bottom nozzle, to prevent the entry of oxygen, is disclosed in JP 11170033. The throughflow of the metal melt through the bottom nozzle is controlled by sliding gates, according to the above-mentioned publications. These sliding gates slide perpendicularly of the throughflow direction of the metal and can thus close the bottom nozzle. Another possibility for throughflow regulation is a so-called plug bar (also termed stopper rod), as known e.g.

from JP 2002143994.

L

In the Korean publication KR 1020030054769 A, the arrangement of a housing around the valve of a bottom nozzle is described. The gas present in the housing is O sucked out by means of a vacuum pump. JP 4270042 describes a similar housing. Here, as in others of the above-mentioned publications, a non-oxidizing atmosphere is produced s within the housing. The housing has an aperture through which the inert gas can be supplied. A further arrangement, in which the gas is sucked out of the housing partially t surrounding the bottom nozzle, in order to produce a vacuum within the housing, is known from JP 61003653.

The present invention has as its object to further improve the present techniques, in io order to minimize the adherence of clogging in the nozzle of a bottom nozzle in a simple N, and reliable manner, without thereby impairing the quality of the metal melt or of the solidified metal.

According to a first aspect of the invention, there is provided a method for regulating the throughflow through a bottom nozzle of a metallurgical vessel, with an Is upper nozzle arranged in the floor of the metallurgical vessel and a lower nozzle arranged below the upper nozzle, with at least one inert gas inlet aperture and with a sensor arranged on or in the lower nozzle for determining the layer thickness of clogging in the nozzle, the inert gas supply into the bottom nozzle being regulated using the measurement signals of the sensor.

According to a second aspect of the invention, there is provided a bottom nozzle for a metallurgical vessel for performing the method according to the first aspect, with an upper nozzle arranged in the floor of a metallurgical vessel and a lower nozzle arranged below the upper nozzle, at least one inert gas aperture with an inert gas connection being arranged below the upper nozzle, and a sensor being arranged on or in the outside of the lower nozzle for determining the layer thickness of clogging in the nozzle, whereby the sensor is connected with a flow control for the inert gas.

According to a third aspect of the invention, there is provided a bottom nozzle for a metallurgical vessel with an upper nozzle arranged in the floor of a metallurgical vessel and a lower nozzle arranged below the upper nozzle, the wall of the throughflow aperture through the nozzles being formed at least sealed to metal melt flow, wherein the nozzles are at least partially surrounded by a gastight housing; wherein the housing encloses at its lower end the lower nozzle at its periphery, abutting with a portion of its inner side on the outside of the nozzle, and wherein a thermally insulating solid is arranged between the wall of the throughflow aperture and the housing.

2a According to a fourth aspect of the invention, there is provided throughflow through a bottom nozzle regulated by the method of the first aspect.

SAccording to a fifth aspect of the present invention, there is provided a bottom nozzle according to the second or third aspect-when used in a metallurgical vessel.

According to a method according to the invention for regulating the throughflow through a bottom nozzle of a metallurgical vessel, with an upper nozzle arranged in the Sfloor of the metallurgical vessel, and a lower nozzle arranged below the upper nozzle, with at least one inert gas inlet aperture and with a sensor arranged on or in the lower N nozzle for determining the layer thickness of the clogging in the nozzle, the inert gas 0 o supply into the bottom nozzle is regulated using the measurement signals of the sensor.

N In particular, starting from an existing throughflow quantity of the inert gas or an existing pressure of the inert gas, the throughflow quantity and/or the pressure is reduced until the sensor signals an increase of clogging and/or the throughflow quantity and/or the pressure are increased until the sensor signals a decrease or release of the clogging. The inert gas flow can thereby be reduced to a minimum, so that little inert gas is introduced into the metal melt and consequently little inert gas is present in the finished metal, for example steel. A temperature sensor arranged on or in the outside of the lower nozzle is preferably used as the sensor. Instead of a temperature sensor a resistive sensor, an inductive sensor, an ultrasonic detector or an x-ray detector can also be used for the measurement. It is appropriate that the throughflow quantity and/or the pressure is reduced until the measured wall temperature falls more rapidly than a predetermined threshold value of cooling and/or that the throughflow quantity and/or the pressure is/are increased until the measured wall temperature falls less rapidly than a predetermined threshold of cooling. It can in particular be advantageous that the flow of metal melt is regulated by means of a valve arranged between the upper and the lower nozzle or above the upper nozzle. In the former case, a sliding gate is used between the upper and the lower nozzles; in the latter case, a stopper rod. It is appropriate that the introduction of the inert gas into S the throughflow aperture of the bottom nozzle takes place below the upper nozzle. Argon is C-i preferably used as the inert gas.

According to the invention, a bottom nozzle for a metallurgical vessel for performing the method has an upper nozzle arranged in the floor of a metallurgical vessel and a lower nozzle arranged below the upper nozzle, at least one inert gas aperture with an inert gas connection being arranged below the upper nozzle, and a sensor, preferably a temperature sensor, being S arranged on or in the outside of the lower nozzle for determining the layer thickness of clogging S in the nozzle, whereby the sensor (10) is connected with a flow control for the inert gas. At least one of the nozzles can appropriately have a heating means. It is reasonable that a valve (sliding jto gate or stopper rod) is arranged below or above the upper nozzle for regulating the flow of metal melt.

A further bottom nozzle according to the invention for a metallurgical vessel, with an upper nozzle arranged in the floor of a metallurgical vessel and a lower nozzle arranged below the upper nozzle, has a wall, at least sealed to flow of metal melt, of the throughflow aperture Is through the nozzles, the nozzles being at least partially surrounded by a gastight housing such that the housing gastightly encloses the lower end of the lower nozzle at its periphery, wherein it abuts on the outside of the nozzle with a portion of its inner side, and that a thermally insulating solid is arranged between the wall of the throughflow aperture and the housing. The term ,,at least partially" means that of course the nozzles can not surrounded by the housing for example at their openings. The housing prevents the penetration of gas. It has an upper end and a lower end and is gastight between these ends. With this arrangement, the bottom nozzle has two basic seals, namely a melt flow seal in the region of the wall of the throughflow aperture and a gas seal in the colder region of the bottom nozzle remote from the throughflow aperture. Thereby fewer temperature-resistant materials can be used for achieving gastightness. By "gastight", absolute gastightness is of course not to be understood, but a smaller gas flow is possible, for example less than 10 ml/s, preferably less than 1 ml/s, in particular preferably about of the order of 1 0 4 ml/s, depending on the kind and location of the seals/materials. Such a value is smaller by at least an order of magnitude than in the known prior art. The minimisation of clogging is the result of the gastightness (especially oxygentightness).

The housing preferably has plural housing portions, gastightly connected together and preferably arranged one above the other, at least one housing portion being gastightly connected to the upper nozzle and/or the floor of the metallurgical vessel, preferably abutting with a portion of its side surface on the outside of the upper nozzle and/or of the floor. It is furthermore appropriate that a valve for regulating the metal melt flow is arranged above the upper nozzle, or between the upper and lower nozzles. In the former case, the valve is a stopper rod; in the latter case, a sliding gate. Preferably a permanent getter material, particularly from the group c-i titanium, aluminum, magnesium or zirconium, is arranged within the housing or in the thermally insulating material.

The housing is appropriately formed as at least partially tubular (hollow cylinder) or conical, preferably with oval or circular cross section.

The housing can appropriately be constructed of steel, and the thermally insulating material can preferably contain aluminum oxide. It can be reasonable that at least one of the nozzles has a heating means.

The invention is explained hereinafter by way of example using a drawing.

Figure 1 shows a bottom nozzle for performing the method according to the invention, Figure 2 shows a time diagram of temperature/pressure, Figure 3 shows a bottom nozzle sealed according to the invention.

The bottom nozzle shown in Figure 1 in the floor of a distributor for steel melt 2 has an upper nozzle 3 within the floor 1. Electrodes 4 for producing an electrochemical effect or as heaters are arranged in this nozzle 3. The floor I itself has different layers of a refractory material and a steel housing 5 on its outside. A sliding gate 6 for regulating the flow of steel melt is arranged below the upper nozzle 3, and below it a lower nozzle 7 which projects into the metal melt container 8, which for example belongs to a continuous casting plant for the steel. The steel melt 2 flows through apertures 9 into the metal melt container 8. A temperature sensor measures the temperature at the outside of the lower nozzle. When this temperature falls, this indicates an increase of clogging within the lower nozzle 7, since the insulation between the outside of the lower nozzle 7 and the steel melt 2 flowing through increases. The temperature sensor 10, together with the pressure sensor 11, effects the regulation of the argon supply through the inert gas aperture 13 to the metal melt 2 via a pressure regulation 12.

A pressure/temperature course with time is shown in Figure 2. With falling temperature (thick line), the argon pressure is increased stepwise, so that the argon flow into the throughflow aperture causes a release of the clogging on the wall. Thereafter the temperature measured on the outer wall rises again as far as a value which remains constant. The argon pressure/argon flow can in this way be set to a minimum at which the formation of clogging is just prevented or kept slight.

O The bottom nozzle shown in Figure 3 has a basically two-part seal, namely a seal which ri seals to melt flow along the inside of the throughflow aperture and a housing 14 which effects a S gastight sealing to the outside (between the atmosphere of the environment and the throughflow C aperture), the individual seals being arranged in a clearly lower temperature region. The houss ing 14 consists of plural portions 14a and 14b and in principle is extended into the metal sleeve which encloses the upper nozzle 3 on its outside and opens into a flange 16, on which a S portion of the outer surface of the upper housing portion 14b is sealingly arranged. The various seals are shown in the Figure. So-called type 1 seals 17 exist between opposed movable portions on the sliding gate 6. They are at least partially exposed to the metal melt. Type 2 seals 18 are arranged between refractory portions of the bottom nozzle 1, i.e. for example between portions of the sliding gate 6 and the upper nozzle 3 or the lower nozzle 7. These type 2 seals 18 C are also at least partially directly exposed to the metal melt or to the temperature of the liquid steel. Furthermore, the wall of the throughflow aperture of the bottom nozzle 1 itself represents a seal (type 3 seal), which is influenced by the choice of material. The seals described above are in principle present in all known arrangements. They can, for example, be formed of aluminum oxide. The sealing effect of the type 3 seals can be improved by high temperature glass layers, among other things. The portions of the outer housing 14 form a type 4 seal, which are not exposed to steel melt or to comparable temperatures. These seals can be formed of metal, for example steel, or from dense sintered ceramic material. Type 5 seals 19 are between portions of the housing 14 and movable portions of the throughflow regulation means, such as the push rods 20 of the sliding gate 6. They are not exposed to liquid steel and, according to the specific temperature conditions, can consist of Inconel (up to 800 0 of aluminum, copper, or graphite (up to about 450 0 or of an elastomeric material (at temperatures up to about 200 0

C),

and also the type 6 seals 20 between the individual housing portions. Furthermore, type 7 seals 21 exist as a transition between the refractory material of the upper nozzle 3 or the lower nozzle 7 and the housing 14 or metal sleeve 15 surrounding these on the outside, and prevent gas, particularly oxygen, from penetrating along at the connection place between these components into the cavity 22 between the housing portion 14b and the sliding gate 6. A reduced pressure is thereby ensured within the cavity 22 with respect to its surroundings during the throughflow of metal melt 2 through the bottom nozzle 1. This type 7 seal can be produced and set by the manufacturer of the nozzles.

The upper nozzle 3 can be formed of zirconium dioxide, and the lower nozzle of aluminum oxide. Foam-type aluminum oxide with low density and closed pores can also be used, likewise aluminum oxide-graphite, other refractory foamed materials or fiber materials. An oxygen getter material, for example titanium, aluminum, magnesium, yttrium or zirconium, can be 0 arranged in the thermally insulating material of the lower nozzle 7 or between the lower nozzle 7 C1 and the housing portion 14a, as a mixture with the refractory insulating material or as a separate portion.

SThe bottom nozzle according to the invention has a substantially smaller leakage rate than known systems. Type 1 or type 2 seals have a leakage rate of about 10 3 -10 4 or 102-103, ml/s, and standard materials for type 3 seals lead to leakage rates of 10-100 ml/s. Type 4 seals S lead to a leakage rate of negligibly less than 10 8 ml/s when metal (for example steel) is used as 0 the material. Type 5 and type 6 seals, when polymer material is used, have a leakage rate of about 104 ml/s and, with the use of the corresponding graphite seals, reach a leakage rate of io. about 1 ml/s. Type 7 seals are similar to a combination of type 3 and type 4 seals, and can reach a leakage rate of 1-10 ml/s. The leakage rates are related to the operating state of the C bottom nozzle.

The standardized leakage rate (Nml/s) leakage rate (ml/s) x pav,/ 1 atm x 273KTavg Pavg (Pin Pout)/2 <atm> Ta, (Tin Tout)/2 <K> avg average value.

Thereby the standardized leakage rate according to the invention is of the order of magnitude of 1-10 Nml/s, while the combination of type 1, type 2 and type 3 seals leads in the best case to 150 Nml/s.

Claims

1. Method for regulating the throughflow through a bottom nozzle of a Smetallurgical vessel, with an upper nozzle arranged in the floor of the metallurgical vessel and a lower nozzle arranged below the upper nozzle, with at least one inert gas inlet aperture and with a sensor arranged on or in the lower nozzle for determining the layer thickness of clogging in the nozzle, the inert gas supply into the bottom nozzle being t regulated using the measurement signals of the sensor.

2. Method according to claim 1, wherein, starting from an existing throughflow Squantity of the inert gas or an existing pressure of the inert gas, the throughflow quantity and/or the pressure is reduced until the sensor signals an increase of clogging, and/or the C throughflow quantity and/or the pressure are increased until the sensor signals a decrease or release of the clogging.

3. Method according to claim 1 or 2, wherein a temperature sensor arranged on or in the outside of the lower nozzle is used as the sensor.

4. Method according to claim 3, wherein the throughflow quantity and/or the pressure is/are reduced until the measured wall temperature falls more rapidly than a predetermined threshold value of cooling, and/or that the throughflow quantity and/or the pressure is/are increased until the measured wall temperature falls less rapidly than a predetermined threshold value of cooling.

5. Method according to any one of claims 1 to 4, wherein the flow of metal melt can be regulated by means of a valve arranged above or below the upper nozzle.

6. Method according to any one of claims 1 to 5, wherein the introduction of the inert gas into the throughflow aperture of the bottom nozzle takes place below the upper nozzle.

7. Method according to any one of claims 1 to 6, wherein argon is used as the inert gas.

8. Bottom nozzle for a metallurgical vessel for performing the method according to any one of claims 1 to 7, with an upper nozzle arranged in the floor of a metallurgical vessel and a lower nozzle arranged below the upper nozzle, at least one inert gas aperture with an inert gas connection being arranged below the upper nozzle, and a sensor being arranged on or in the outside of the lower nozzle for determining the layer thickness of clogging in the nozzle, whereby the sensor is connected with a flow control for the inert gas.

9. Bottom nozzle according to claim 8, wherein the sensor is a temperature sensor. 8 Bottom nozzle according to claim 8 or 9, wherein at least one of the nozzles U has a heating means. d

11. Bottom nozzle according to any one of claims 8 to 10, wherein a valve for regulating the flow of metal melt is arranged above or below the upper nozzle.

12. Bottom nozzle for a metallurgical vessel with an upper nozzle arranged in the floor of a metallurgical vessel and a lower nozzle arranged below the upper nozzle, the Swall of the throughflow aperture through the nozzles being formed at least sealed to metal melt flow, wherein the nozzles are at least partially surrounded by a gastight housing; wherein the housing encloses at its lower end the lower nozzle at its periphery, abutting lio with a portion of its inner side on the outside of the nozzle, and wherein a thermally insulating solid is arranged between the wall of the throughflow aperture and the housing.

13. Bottom nozzle according to claim 12, wherein the housing has plural, gastightly interconnected, housing portions at least one housing portion being connected to the upper nozzle and/or the floor.

14. Bottom nozzle according to claim 13, wherein the housing portions are arranged one above the other. Bottom nozzle according to claim 13 or 14 wherein the housing portion abuts with a portion of its side surface on the outside of the upper nozzle and/or the floor.

16. Bottom nozzle according to any one of claims 12 to 15, wherein a valve for regulating the flow of metal melt is arranged above the upper nozzle or between the upper and the lower nozzles.

17. Bottom nozzle according to any one of claims 12 to 16, wherein a getter material is arranged within the housing or in the thermally insulating material.

18. Bottom nozzle according to claim 17 wherein the getter material is titanium, aluminium, magnesium or zirconium.

19. Bottom nozzle according to any one of claims 12 to 18, wherein at least a portion of the housing is formed with tubular or conical form. Bottom nozzle according to claim 19 when the housing is formed with an oval or circular cross section.

21. Bottom nozzle according to any one of claims 12 to 20, wherein the housing is constructed of steel and wherein the thermally insulating material contains aluminium oxide.

22. Bottom nozzle according to claim 21, wherein the thermally insulating material predominantly contains aluminium oxide. [R:\LIBFFjOS5S3.doc:aak

23. Bottom nozzle according to any one of claims 12 to 22, wherein at least one of the nozzles has a heating means. a 24. Method for regulating the throughflow through a bottom nozzle of a metallurgical vessel, substantially as hereinbefore described with reference to any one of the accompanying drawings. A bottom nozzle for a metallurgical vessel, substantially as hereinbefore t described with reference to any one of the accompanying drawings.

26. Throughflow through a bottom nozzle regulated by the method of any one of Cclaims I to 7 or 24.

27. A bottom nozzle according to any one of claims 8 to 23 or 25 when used in a N metallurgical vessel.

28. Bottom nozzle for a metallurgical vessel with an upper nozzle arranged in the floor of a metallurgical vessel and a lower nozzle arranged below the upper nozzle, the wall of the throughflow aperture through the nozzles being formed at least sealed to metal is melt flow, wherein the nozzles are at least partially surrounded by a gastight housing; wherein the housing encloses at its lower end the lower nozzle at its periphery, abutting with a portion of its inner side on the outside of the nozzle, wherein a thermally insulating solid is arranged between the wall of the throughflow aperture and the housing and wherein the housing prevents the penetration of gas and has an upper end and a lower end and is gastight between these ends.

29. Bottom nozzle according to claim 28, wherein the housing has plural, gastightly interconnected, housing portions, at least one housing portion being connected to the upper nozzle and/or the floor. Bottom nozzle according to claim 29, wherein the housing portions are arranged one above the other.

31. Bottom nozzle according to claim 29 or 30, wherein the at least one housing portion abuts with a portion of its side surface on the outside of the upper nozzle and/or the floor.

32. Bottom nozzle according to any one of claims 28 to 31, wherein a valve for regulating the flow of metal melt is arranged above the upper nozzle or between the upper and the lower nozzles.

33. Bottom nozzle according to any one of claims 28 to 32, wherein a getter material is arranged within the housing or in the thermally insulating material.

34. Bottom nozzle according to claim 33, wherein the getter material is titanium, aluminium, magnesium or zirconium.

1055047-IHJG Bottom nozzle according to any one of claims 28 to 34, wherein at least a Sportion of the housing is formed with tubular or conical form. 36. Bottom nozzle according to claim 35 when the housing is formed with an oval or circular cross section. 37. Bottom nozzle according to any one of claims 28 to 36, wherein the housing is constructed of steel and wherein the thermally insulating material contains aluminium Soxide. 38. Bottom nozzle according to claim 37, wherein the thermally insulating r material predominantly contains aluminium oxide. 39. Bottom nozzle according to any one of claims 28 to 38, wherein at least one ri of the nozzles has a heating means. A bottom nozzle for a metallurgical vessel as claimed in claim 28, substantially as hereinbefore described with reference to any one of the accompanying drawings. Is 41. A bottom nozzle according to any one of claims 28 to 40 when used in a metallurgical vessel. Dated 13 December, 2007 Heraeus Electro-Nite International N.V. Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON 1055047-IHJG