WO2005080612A1

WO2005080612A1 - Device for treating liquid metal in a ladle

Info

Publication number: WO2005080612A1
Application number: PCT/EP2005/050164
Authority: WO
Inventors: Jean-Jacques Willieme; Frederic Parasch; Alphonse Decker; Dominique Rocchi
Original assignee: Sms Mevac Gmbh; Lonardi, Emile
Priority date: 2004-02-24
Filing date: 2005-01-17
Publication date: 2005-09-01
Also published as: EP1568790A1

Abstract

The present invention relates to a device for treating liquid metal in a ladle, including a rotary hood provided with a bearing enabling rotation thereof, which bearing includes an upper portion rigidly connected to the hood and a freely rotatable lower portion, a drive device for rotating the hood about a vertical axis, and a hood handling device. The handling device includes a first rotary hood locking means engageable with the lower bearing portion from below so that it bears the weight of the hood, as well as a second rotary hood locking means engageable with the lower bearing portion from above so that it prevents upward movement of the hood.

Description

DEVICE FOR THE TREATMENT OF POCKET LIQUID METAL

The present invention relates to a device for treating liquid metal, in particular ladle steel. At the present time, there are a series of methods for treating liquid metal, in particular ladle steel, according to which a bell or a tube is immersed in the molten metal contained in a ladle. Such processing methods are among others the so-called CAS, CAS-OB, HALT methods, etc. In this type of process, the liquid metal contained in the bag is subjected to various treatments in a confined area, delimited by the bell plunging into the liquid metal. Below the bell, a bubbling gas is injected into the liquid metal to homogenize it during the treatment. Turbulence therefore forms on the surface of the liquid metal which leads to increased local wear of the bell on its lower edge. PCT patent application WO98 / 31841 describes a process aimed at minimizing local wear of a bell during treatment of a liquid metal in a ladle. The bell is rotated around its perpendicular axis in order to minimize local wear of the bell during the processing of liquid metal in the ladle. As the bell rotates during the processing of the liquid metal, increased wear at a given location due to turbulence in the liquid metal is no longer to be feared. The bell wears out regularly around its entire periphery. Such rotating bells are particularly useful during the implementation of the method for the treatment of liquid steel in a ladle described in European patent EP 0 110 809. In such a method, by which the steel contained in the pocket by aluminothermy and by which a certain number of alloying elements are added to the steel, the bell is stressed asymmetrically: - on a "hot" side, the bell or more precisely the refractory lining of the lower edge of the bell is attacked by thermal shock and by chemical corrosion under the effect of projections of metal and slag. The wear is mainly caused by flaking of the refractory lining. - on the "cold" side and possibly in intermittent use when the refractory has cooled, the bell "greases" by solidification of metal and / or slag projections. These phenomena of local wear and "fattening" considerably reduce the life of the bell and thus increase the cost of production by the process of addition and heating under a bell. The use of a rotating bell prolongs the duration of use of a refractory bell, by minimizing local wear and reducing the local fattening. Normally these rotating bells are suspended in a clamp so as to allow their rotation around their vertical axis and are lowered into the liquid metal bath by means of an appropriate device. It is important for the proper functioning of such bells to be able to guarantee a certain depth of penetration of the lower edge of the bell in the liquid metal However, it has been surprisingly found that, under certain conditions, the bells which can weigh several tons, begin to float on the liquid metal in the pocket. In these conditions and given the suspension mechanisms used, there is no It is not possible to guarantee a constant depth of penetration. The problem underlying the invention therefore consists in proposing a rotary bell for the treatment of e liquid metal in a pocket which can be maintained at a certain depth of penetration determined in the metal under all conditions. Usually, the penetration depth of such a bell is about 10-50 cm and preferably between 20 and 40 cm, i.e. the lower edge of the bell is immersed over a distance of 10 to 50 cm below the surface of the liquid metal, if necessary covered with slag. To achieve this objective, the present invention provides a device for processing liquid metal in a bag comprising a rotary bell equipped a bearing allowing a rotational movement of the bell, the bearing comprising an upper part integral with the bell and a lower part which can rotate freely, a drive device making it possible to drive the bell in a rotational movement around a vertical axis and a device for handling the bell. Said handling device comprises: • a first means for blocking the rotary bell which can engage the lower part of the bearing from below so as to support the weight of the bell, • a second means for blocking the rotary bell which can engage the part bottom of the bearing from above so as to prevent the vertical movement upwards of the bell. Even if slag fattenings form on the lower edge of the bell which increase the buoyancy, the bell can be maintained at a predetermined immersion depth. The bell driving device is thus also protected. According to a first advantageous embodiment, the first locking means of the rotary bell comprises a first clamp capable of engaging the bell below the lower part of the bearing of the stop. The second locking means of the rotary bell can either comprise one or more jacks bearing on the top of the lower part of the bearing or else a second clamp capable of engaging the bell above the lower part of the bearing. stop. According to another embodiment, the first locking means and the second locking device are made in one piece comprising a V-shaped notch which can be engaged in the lower part of the bearing. The drive device can advantageously comprise a toothed crown secured to the bell driven by a motor by means of a toothed wheel. The speed of rotation of the bell is usually between 0.5 and 2 revolutions / min during the treatment of the liquid metal. The speed of rotation of the bell can be adapted according to the diameter of the bell, according to the treatment applied to the liquid metal and / or according to the composition and the viscosity of the slag which covers the liquid metal in the pocket. Of course, the bell can continue to rotate around its axis even when it is removed from the bath after the treatment of the liquid metal. The bell is rotated about a vertical axis, substantially perpendicular to the surface of the molten metal or the molten steel, respectively. A preferred embodiment of an installation according to the invention is described with the aid of the appended drawings, in which:

- Figure 1 shows a cross section of a bell and a bag filled at rest;

FIG. 2 shows an enlargement in section of a device for driving the bell,

- Figure 3 shows an overview of the bell handling device when loading a bell,

- Figure 4 shows a coupling sequence of a bell according to a first embodiment, - Figure 5 shows a coupling sequence of a bell according to a second embodiment,

FIG. 6 shows a sequence for coupling a bell according to a third embodiment,

- Figure 7 shows an enlargement of the coupling device of Figure 6. A bag 10 (Fig.1) comprising a refractory lining 15, filled with liquid steel 20 is placed on a carriage 25 and is brought below a refractory bell 30. In the working position, during metal processing liquid, the bell 30 is lowered until its lower edge 40 is immersed in the liquid steel 20. The bell 30 is connected to a supply conduit 50 (FIG. 2) by which the combustible materials and the elements alloys are introduced into the liquid steel 5. It comprises a driving device 60 which can drive the bell in a rotational movement around a vertical axis. An inert or reducing bubbling gas can be introduced into the liquid steel 20 either by a porous plug (not shown) arranged in the bottom of the pocket 10 or by a lance (not shown) which is introduced into the pocket 10. This bubbling gas is used to homogenize the liquid steel 20 contained in the pocket 10 during the treatment of the steel 20. This bubbling gas creates turbulence on the surface of the steel 20 which causes local wear of the bell 30 and in particular of the lower edge 40 of the bell 30. FIG. 2 shows an enlarged view of the drive device 60 of the bell 30. The upper end of the bell 30 comprises a ball bearing 70 integral with the bell 30 which allows the bell 30 to perform a rotational movement about its vertical axis. The upper part 75 of the bearing 70 is ι ^λ i fixed to the bell 30 while the lower part δO of the bearing 70 can rotate freely. When the bearing 70 is not under stress, the lower part 80 rests against a stop 85 arranged below the bearing 70. Of course, this bearing 70 must be protected against the penetration of impurities. The bell 30 is held in position by means of a blocking system bearing from below and from above on the lower part 80 of the bearing 70 which pushes the bell 30 against the supply duct 50. On the 25 upper part 75 of the bearing 70 is arranged a toothed crown 90. The rotation of the bell 30 is carried out using a motor 100 preferably comprising a reduction gear 110 making it possible to vary the speed of rotation of the bell 30. The motor 100 drives the ring gear 90 by means of a toothed wheel 120 integral with the motor 100. Of course, there are other means well known to those skilled in the art for impregnating a rotational movement with such a bell. The tightness of the supply duct 50 relative to to the bell 30 is provided by a baffle 130. The bell 30 and the supply duct 50 comprise an internal coating of refractory material. This coating is not shown in the figures for reasons of clarity of the drawing. In FIG. 3, the pocket 10, placed on a carriage 140, is brought below a bracket 150 which comprises a movable platform 160, equipped with a bell 10, a mast 170 and a drive device 180 on the top of it. The platform 160 is connected to the drive device 180 by means of a belt 190 by means of which the platform can be moved vertically on the mast 170 using the wheels 200 which bear on the mast of the stem. Figures 4, 5 and 6 show, in section, switching sequences of three different locking mechanisms of the bell. In order not to overload the drawings, only the lower part 80 of the bearing 70 has been shown. The first series of Figures 4a), 4b), 4c) and 4d) show, in section, a first embodiment of the present invention in which the first locking means and the second locking device are made in one piece comprising a V-shaped notch that can snap onto the lower part of the bearing. In FIG. 4a), the platform 160 is lowered on the upper part

210 from the bell 10 to below the lower part 80 of the bearing. The platform 160 is then raised until the V-shaped locking device 220 is at the level of the lower part 80 of the bearing (FIG. 4b). In Figure 4c), the V-shaped locking device is closed to block the bell 10 thus preventing downward and upward movement of the bell 10. The bell is then lifted (Figure 4d) rest position (see Figure) On the following two series, the locking devices are produced in two separate parts. In FIG. 5a), the platform 160 is lowered on the upper part 210 of the bell 10 as far as below the lower part 80 of the bearing. The first locking device 230 in this case a clamp - is then brought into the closed position (FIG. 5b) and the platform 160 is then raised until the first locking device 230 touches the lower part 80 of the landing from below (Figure 5c). The second locking device is then closed and prevents any movement of the bell upwards. The bell is then lifted and brought to the resting position. In the case of FIG. 5, the second locking device comprises four cylinders spaced regularly (only two are shown in FIG. 5). They are mounted on the platform using arms 250. The jacks 240 are then brought into the closed position and bear from above the lower part of the bearing of the bell (Figure 5d)). In the case of FIG. 6, the second locking device is a clamp 260 superimposed on the first clamp 230. The second clamp 260 is closed and thus blocks the bearing to prevent any upward movement. In Figure 7, the two clamps 230, 260 for blocking are shown with more details in the open position around the upper part of the bell., Table of references

10 pocket

15 refractory lining

20 liquid steel

25 pocket trolley

30 refractory bell

40 bottom edge

50 supply line

60 drive device

70 ball bearing

75 upper part of the bearing

80 lower part of the bearing

85 stop 90 toothed crown

100 motor

110 reducer

120 gear wheel

130 chicane

140 bell carriage

150 gallows

160 platform

170 mat

180 drive device

190 belt

200 wheels

210 upper part of the bell

220 V-shaped locking device

230 first locking device (first clamp)

240 cylinder

250 arms

260 second locking device (second clamp)

Claims

1. Device for processing liquid metal in a bag comprising a rotary bell equipped with a bearing allowing the bell to rotate, the bearing comprising an upper part secured to the bell and a lower part which can rotate freely, a device for drive for driving the bell in a rotational movement around a vertical axis and a device for handling the bell, said handling device comprising: • a first means for locking the rotary bell which can engage the lower part of the bearing from below so as to support the weight of the bell • a second means for locking the rotary bell which can engage the lower part of the bearing from above so as to prevent vertical movement upwards of the bell.

2. Device according to claim 1, characterized in that the first locking means of the rotary bell comprises a first clamp which can surround the bell below the lower part of the bearing of the stop.

3. Device according to claim 1 or 2, characterized in that the second locking means of the rotary bell comprises one or more cylinders bearing on the top of the lower part of the bearing.

4. Device according to claim 1 or 2, characterized in that the second locking means of the rotary bell comprises a second clamp which can surround the bell above the ring

5. Device according to claim 1, characterized in that the first locking means and the second locking device are made in one piece comprising a V-shaped notch which can engage on the lower part of the bearing.

6. Device according to any one of the preceding claims, characterized in that the drive device comprises a crown toothed integral with the bell driven by a motor by means of a toothed wheel.