EP1661645A2 - Process for regulating the flow rate and bottom tap hole for metallurgical vessel - Google Patents

Abstract

A method for controlling flow through the bottom outlet of a metallurgical vessel with an upper nozzle (3) in the base (1), a lower nozzle (7) below (3), inert gas inlet(s) (13) and a sensor (10) on or in the lower nozzle (7) to measure the thickness of solid in the nozzle (clogging), in which the inert gas feed to the outlet is controlled by means of the signal from the sensor. Independent claims are also included for (1) a bottom outlet as described above (BO1) in which the inert gas inlet(s) and connection(s) are below the upper nozzle (3) and the sensor (10) is on or in the outside of the lower nozzle (7) and is also connected to an inert gas flow controller (2) a bottom outlet as above (BO2) in which the wall of the connecting opening between (3) and (7) is liquid-tight, at least with regard to molten metal, and the two nozzles (3, 7) are surrounded by a gas-tight housing (14) which forms a gas-tight seal with (7) at the bottom of the housing (14), with part of its inside on the outside of (7) and with a thermally-insulating solid between the wall of the connection (3:7) and the housing (14) .

Description

The invention relates to a method for regulating the flow through a bottom spout of a metallurgical vessel. Furthermore, the invention relates to a floor spout of a metallurgical vessel.

In particular, with molten steel, the liquid metal is poured from a distributor, for example, in a continuous casting plant. It flows through a floor spout in the bottom of the distributor housing (a so-called Nozzle). A disadvantage is the adhesion of material to the wall of the floor spout during the flow. This reduces the opening cross section, so that the flow conditions are adversely affected. In order to prevent adhesion of material to the wall, an inert gas such as argon is often introduced into the flow opening. Excessively large quantities of gas, however, can adversely affect the quality of the steel, for example, by creating voids in the steel which cause surface damage when the steel is rolled out.

A material for a floor spout is described, for example, in WO 2004/035249 A1. A floor spout within a metallurgical vessel is disclosed in KR 2003-0017154 A or in US 2003/0116893 A1. In the latter document is shown on the use of inert gas with the aim to reduce the adhesion of material to the inner wall of the floor spout (so-called clogging), similar to that described in JP 2187239. A mechanism with a gas supply regulation from WO 01/56725 A1 is quite well known. Nitrogen is supplied according to Japanese Publication JP 8290250. JP 3193250 discloses a method of observing adherence of material by means of a plurality of temperature sensors arranged longitudinally of the bottom spout. The introduction of inert gas into the interior of the floor spout is also known, inter alia, from JP 2002210545, JP 61206559, JP 58061954 and JP 7290422.

It is also known from some of these documents, in addition to the supply of inert gas, to prevent oxygen access as much as possible by using housings around part of the floor spout. In some cases, as in JP 8290250, for example, an inert gas overpressure is generated within such a housing. To prevent the ingress of oxygen, a housing is disclosed in JP 11170033 around a valve of the floor spout. The flow of molten metal through the bottom spout is controlled by spool valves in accordance with the above references. These slides slide perpendicular to the flow direction of the metal and can thereby close the bottom spout. Another possibility of the flow control is a so-called stopper rod (also called stopper rod), as known for example from JP 2002143994.

The Korean document KR 1020030054769 A describes the arrangement of a housing around the valve of a floor spout. The gas in the housing is sucked by means of a vacuum pump. JP 4270042 describes a similar housing.
Here, as in other references mentioned above, a non-oxidizing atmosphere is created within the housing. The housing has an opening through which inert gas can be supplied. Another arrangement in which gas is aspirated from the housing partially surrounding the bottom spout to create a vacuum within the housing is known from JP 61003653.

It is an object of the present invention to further improve the existing techniques to easily and reliably minimize the sticking of fixings in the nozzle of a floor spout without compromising the quality of the molten metal or solidified metal.

The object is solved by the features of the independent claims. Advantageous embodiments are specified in the subclaims.

According to the inventive method for controlling the flow through a bottom spout of a metallurgical vessel with a arranged in the bottom of the metallurgical vessel upper nozzle and a lower nozzle disposed below the lower nozzle, with at least one inertgaseinlassöffnung and arranged on or in the lower nozzle sensor for determining the layer thickness of fixings in the nozzle, the inert gas supply is controlled in the bottom spout on the basis of the measuring signals of the sensor.

In particular, starting from an existing flow rate of the inert gas or an existing pressure of the inert gas, the flow rate and / or the pressure is reduced until the sensor signals an increase in determinations and / or the flow rate and / or the pressure are increased until the sensor indicates a decrease or a dissolution of the stipulations. In this case, the Inergaszufluss can be minimized to a minimum, so that little inert gas is fed into the molten metal and as a result less gas inclusions in the finished metal, such as steel, are present. Preferably, a temperature sensor arranged on or in the outside of the lower nozzle is used as the sensor. The measurement can also be made inductively, resistively, by means of ultrasound or X-rays. It is expedient that the flow rate and / or the pressure be reduced until the measured wall temperature drops faster than a predetermined limit value of the cooling and / or that the flow rate and / or the pressure are increased until the measured wall temperature is less fast decreases as a predetermined limit of cooling. In particular, it may be advantageous for the molten metal flow to be regulated by means of a valve arranged between the upper and the lower nozzle or a valve arranged above the upper nozzle. In the former case, a slide valve (sliding gate) is used between the upper and lower nozzles, in the latter case a stopper rod. It is expedient that the introduction of the inert gas takes place in the flow opening of the bottom spout below the upper nozzle. Preferably, argon is used as the inert gas.

According to the invention, a bottom spout for a metallurgical vessel for carrying out the method comprises an upper nozzle arranged in the bottom of a metallurgical vessel and a lower nozzle arranged below the upper nozzle, wherein at least one inert gas inlet opening is arranged below the lower nozzle in the flow opening of the bottom spout with an inert gas connection and wherein on or in the outside of the lower nozzle, a sensor, preferably a temperature sensor, is arranged for determining the layer thickness of clogging in the nozzle and wherein the sensor is connected to an inert gas flow regulator. At least one of the nozzles may conveniently have a heater. It makes sense that below or above the upper nozzle a valve (slide valve or stopper rod) is arranged to control the molten metal flow.

Another inventive bottom spout for a metallurgical vessel with an upper nozzle arranged in the bottom of a metallurgical vessel and a lower nozzle arranged below the upper nozzle has an at least molten metal flow-tight design Wall of the flow opening through the nozzles and is characterized in that the nozzles are at least partially surrounded by a gas-tight housing, that the housing gas-tight encloses the lower nozzle at its lower end at its periphery, wherein it with a part of its inside on the outside the nozzle abuts and that between the wall of the flow opening and the housing, a thermally insulating solid is disposed. The term "at least partially" is to be understood as meaning that the housing, of course, can not surround the nozzle, for example, at its orifices. The housing prevents the passage of gas, it has an upper and a lower end and is gas-tight in between. With this arrangement, the floor spout on two basic seals, namely a melt flow seal in the region of the wall of the flow opening and a gas seal in the colder, the flow opening facing away from the bottom spout. As a result, less temperature-resistant materials can be used to achieve the gas-tightness. Under gas-tight course, no absolute gas tightness is to be understood, but a low gas flow is possible, for example, less than 10 ml / s, preferably less than 1 ml / s, more preferably about the order of 10 ⁴ ml / s, depending on the type and location of seals / materials. Such a value is at least an order of magnitude less than in the known prior art. This gas tightness (especially oxygen tightness) is responsible for minimizing clogging.

The housing preferably has a plurality of gas-tight connected, preferably superimposed housing parts, wherein at least one housing part with the upper nozzle and / or the bottom of the metallurgical vessel is connected gas-tight, preferably by having a part of its side surface on the outside of the upper Nozzle and / or the soil is applied. It is expedient, furthermore, that a valve for regulating the molten metal flow is arranged above the upper nozzle or between the upper and the lower nozzle. In the former case, the valve is a stopper rod, in the second case a slide valve. Within the housing or in the thermally insulating material is preferably an oxygen getter material, in particular from the group of titanium, aluminum, magnesium or zirconium arranged.

The housing is expediently at least partially tubular (hollow cylinder) or conical, preferably formed with an oval or circular cross-section. The housing may conveniently be formed of steel and the thermally insulating material may preferably contain alumina. It may make sense that at least one of the nozzles has a heater.

Figur 1

einen Bodenausguss zur Durchführung des erfindungsgemäßen Verfahrens,

Figur 2

ein Temperatur/Druck-Zeitdiagramm,

Figur 3

einen erfindungsgemäß abgedichteten Bodenausguss.

The invention will be explained by way of example with reference to a drawing. In the drawing shows:

FIG. 1

a floor spout for carrying out the method according to the invention,

FIG. 2

a temperature / pressure time diagram,

FIG. 3

a sealed according to the invention bottom spout.

The bottom spout shown in Figure 1 in the bottom 1 of a distributor for molten steel 2 has within the bottom 1 an upper nozzle 3. In this electrodes 4 are arranged to produce an electrochemical effect or as a heater. The floor 1 itself has various layers of a refractory material and on its outer side a steel housing 5. Below the upper nozzle 3, a slide valve 6 is arranged to control the molten steel flow and below a lower nozzle 7, which extends into the molten metal container 8, which belongs for example to a continuous casting plant for the steel. Through openings 9, the molten steel 2 flows into the molten metal container 8. A temperature sensor 10 measures the temperature on the outside of the lower nozzle. If this decreases, this indicates a growth of the fixings within the lower nozzle 7, since the insulation between the outside of the lower nozzle 7 and the flowing molten steel 2 increases. The temperature sensor 10, together with the pressure sensor 11 via a pressure control 12, the control of the argon supply through the Inertgaseinlassöffnung 13 to the molten metal second

FIG. 2 shows a time pressure / temperature profile. As the temperature decreases (thick line), the argon pressure is gradually increased so that the flow of argon into the flow passage causes dissolution of the wall fixings. As a result, the temperature measured on the outer wall increases again to a constant value. In this way, argon pressure inflow can be minimized, at which the formation of fixes is just prevented or minimized.

The bottom spout shown in Figure 3 has a basically two-part seal, namely a melt flow-tight seal along the inside of the flow opening and a housing 14, which realizes a gas-tight seal to the outside (between the ambient atmosphere and the flow opening), wherein the individual seals in a significantly lower temperature range are arranged. The housing 14 consists of several parts 14a and 14b and is in principle continued in the metal sleeve 15, which comprises the upper nozzle 3 on its outer side and opens into a flange 16, on which a part of the outer surface of the upper housing part 14b is sealingly arranged. In the figure, the various seals are shown. So-called type 1 seals 17 exist between mutually movable parts on the slide valve 6. They are at least partially exposed to molten metal. Type 2 seals 18 are disposed between refractory parts of the bottom spout 1, that is, for example, between the parts of the spool valve 6 and the upper nozzle 3 and the lower nozzle 7. These type 2 seals 18 are the molten metal or the Temperature of liquid steel at least partially exposed directly. Furthermore, the wall of the flow opening of the floor spout 1 itself is a seal (type 3 seal), which is influenced by the choice of material. The above-described seals are in principle also present in all known arrangements. They may be formed of alumina, for example. The sealing effect of the Type 3 seals can be improved, inter alia, by high temperature glass layers. The parts of the outer housing 14 form a type 4 seal which are not exposed to molten steel or temperatures of comparable height. These seals may be formed of metal, for example of steel, or of densely sintered ceramic material. Type 5 seals 19 are located between parts of the housing 14 and moving parts of the flow control, such as the push rods 20 of the slide valve 6. They are not exposed to the liquid steel and can, depending on the specific temperature conditions of Inkonel (up to 800 ° C) , made of aluminum, copper or graphite (up to about 450 ° C) or from one
elastomeric material (at temperatures up to about 200 ° C) may be formed, as well as the type 6 seals 20 between the individual housing parts. In addition, as a transition between the refractory material of the upper nozzle 3 and the lower nozzle 7 and surrounding them on the outside housing 14 and metal sleeve 15 type 7 seals 21, which prevent gas, especially oxygen at the junction along these building parts in the cavity 22 between the housing part 14b and the slide valve 6 penetrate. Thereby, a negative pressure within the cavity 22 is ensured against its environment during the passage of the molten metal 2 through the bottom spout 1. This type 7 seal can be made and adjusted by the manufacturer of the nozzles.

The upper nozzle 3 may be formed of zirconia, the lower nozzle of alumina. Foam alumina with a low density and closed pores may also be used, as well as alumina graphite, other refractory foam or fiber materials. In the thermally insulating material of the lower nozzle 7 or between the lower nozzle 7 and the housing part 14a, an oxygen getter material such as titanium, aluminum, magnesium, yttrium or zirconium may be arranged as a mixture with the refractory insulating material or as a sepatates part.

$${\mathrm{T}}_{\mathrm{avg}}=\left({\mathrm{T}}_{\mathrm{in}}+{\mathrm{T}}_{\mathrm{out}}\right)/2\mathrm{\hspace{0.17em}}<\mathrm{\kappa }>$$

avg = Durchschnittswert.The floor drain according to the invention has a significantly lower leakage rate than known systems. Type 1 and Type 2 seals have a leak rate of approximately 10 ³ to 10 ⁴ and 10 ² to 10 ³ ml / s, respectively, and standard materials for the Type 3 seals result in leakage rates of approximately 10 to 100 ml / s. Type 4 seals result in a leakage rate of negligible less than 10 ^-8 ml / s when metal (such as steel) is used as the material. Type-5 and
Type 6 seals can achieve a leak rate of about 10 ^-4 ml / s using polymer material and using appropriately sized graphite seals of about 1 ml / sec. Type 7 seals are similar to a combination of Type 3 and Type 4 seals and can reach a leak rate of approximately 1 to 10 ml / s. The leak rates refer to the operating condition of the floor spout.
The normalized leak rate (Nml / s) = leak rate (ml / s) xp _avg / 1 atm x 273 K / _avg $${\mathrm{p}}_{\mathrm{avg}}=\left({\mathrm{p}}_{\mathrm{in}}+{\mathrm{p}}_{\mathrm{out}}\right)/2\mathrm{}<\mathrm{atm}>$$

$${\mathrm{T}}_{\mathrm{avg}}=\left({\mathrm{T}}_{\mathrm{in}}+{\mathrm{T}}_{\mathrm{out}}\right)/2\mathrm{}<\mathrm{\kappa }>$$

avg = average value.

Thus, the normalized leak rate according to the invention is on the order of about 1 to 10 nml / s, while the combination of type 1, type 2 and type 3 seals leads at best to 150 Nml / s.

Claims (18)

Method for regulating the flow through a bottom spout of a metallurgical vessel with an upper nozzle (3) arranged in the bottom (1) of the metallurgical vessel and a lower nozzle (7) arranged below the upper nozzle (3) with at least one inert gas inlet opening (13) and with sensor (10) arranged on or in the lower nozzle (7) with which the layer thickness of clogging in the nozzle is determined, the inert gas feed into the bottom nozzle being regulated on the basis of the measuring signals of the sensor (10), A method according to claim 1, characterized in that starting from an existing flow rate of the inert gas or an existing pressure of the inert gas, the flow rate and / or pressure are reduced until the sensor (10) signals an increase of determinations and / or that the flow rate and / or the pressure is increased until the sensor (10) signals a decrease or a resolution of the determinations. A method according to claim 1 or 2, characterized in that as a sensor (10) on or in the outside of the lower nozzle (7) arranged temperature sensor is used. A method according to claim 3, characterized in that the flow rate and / or the pressure are reduced until the measured wall temperature decreases faster than a predetermined limit value of the cooling and / or that the flow rate and / or the pressure is increased until the measured wall temperature decreases less rapidly than a predetermined threshold value of the cooling. Method according to one of claims 1 to 4, characterized in that the molten metal flow can be regulated by means of a valve (6) arranged above or below the upper nozzle (3). Method according to one of claims 1 to 5, characterized in that the introduction of the inert gas takes place in the flow opening of the bottom spout below the upper nozzle (3). Method according to one of claims 1 to 6, characterized in that argon is used as the inert gas. Floor spout for a metallurgical vessel for carrying out the method according to one of Claims 1 to 7, having an upper nozzle (3) arranged in the bottom (1) of a metallurgical vessel and a lower nozzle (7) arranged below the upper nozzle (3), below at least one inert gas inlet opening (13) with an inert gas connection is arranged on the upper nozzle (3), a sensor (10) being arranged on or in the outer side of the lower nozzle (7) for determining the layer thickness of clogging in the nozzle and wherein the sensor is connected to an inert gas flow regulator. Floor spout according to claim 8, characterized in that the sensor (10) is a temperature sensor. Floor spout according to claim 8 or 9, characterized in that at least one of the nozzles (3; 7) has a heater. Floor spout according to one of claims 8 to 10, characterized in that above or below the upper nozzle (3) a valve (6) is arranged for controlling the molten metal flow. Floor spout for a metallurgical vessel with an upper nozzle (3) arranged in the bottom (1) of a metallurgical vessel and one below the upper nozzle (3) arranged lower nozzle (7), wherein the wall of the flow opening through the nozzles (3: 7) is formed at least molten metal flow, characterized in that the nozzles (3; 7) are at least partially surrounded by a gas-tight housing (14) that the Housing (14) at its lower end, the lower nozzle (7) encloses gas-tight at its periphery, wherein it bears with a part of its inner side on the outside of the nozzle (7) and that between the wall of the flow opening and the housing (14) thermally insulating solid is arranged. Floor spout according to Claim 12, characterized in that the housing (14) has a plurality of housing parts (14a, 14b) which are connected to one another in a gas-tight manner, wherein at least one housing part (14b) is connected to the upper nozzle (3) and / or the floor ( 1) is connected in a gastight manner, preferably in that it rests with a part of its side surface on the outside of the upper nozzle (3) and / or the bottom (1). Floor spout according to claim 12 or 13, characterized in that above the upper nozzle (3) or between the upper and the lower nozzle, a valve (6) is arranged for controlling the molten metal flow. Floor spout according to one of claims 12 to 14, characterized in that within the housing (14) or in the thermally insulating material, a getter material, preferably from the group of titanium, aluminum, magnesium or zirconium is arranged. Floor spout according to one of claims 12 to 15, characterized in that at least part of the housing (14) is tubular or conical, preferably with an oval or circular cross-section. Floor spout according to one of claims 12 to 16, characterized in that the housing (14) is formed of steel and that the thermally insulating material preferably contains predominantly alumina. Floor spout according to one of claims 12 to 17, characterized in that at least one of the nozzles (3; 7) has a heater.

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