Control instrument and method for monitoring a plate of an ingot mould in a continuous casting plant

Abstract

 A control instrument (11) for monitoring a plate (10) of an ingot mould (4) in a continuous casting plant (1); the control instrument (11) is provided with: a rigid frame (13) provided with a plurality of feet (14) suited to be laid against a vertical wall (12) of the plate (10); a distance measuring device (20) suited to face the vertical wall (12) so as to measure a distance (D) existing with respect to the vertical wall (12) itself; a moving device (21), which moves the distance measuring device (20) along a vertical measuring path (P); a position sensor (22), which detects the position of the distance measuring device (20) along the vertical measuring path (P); and a processing unit (23), which correlates the distance (D) with respect to the vertical wall (12), which has been measured by the distance measuring device (20), with the position of the distance measuring device (20) along the vertical measuring path (P), so as to obtain a profile of the vertical wall (12) (Fig. 3).

Description

FIELD OF THE ART

[0001] The present invention relates to a control instrument and a method for monitoring a plate of an ingot mould in a continuous casting plant.

[0002] The present invention finds advantageous application in a continuous casting plant for the making of steel bars, to which the following disclosure will explicitly refer while not losing generality therefor.

PRIOR ART

[0003] A continuous casting plant for the making of steel bars comprises a ladle feeding molten metal through a vertical solidification path comprising an ingot mould in which primary solidification of steel occurs. The ingot mould is a tubular body comprised of a set of copper plates that are cooled by a continuous circulation of cooling water.

[0004] The ingot mould has a taper converging towards the bottom (i.e., towards the outlet) so that the cross section of the ingot mould progressively decreases from the upper inlet to the lower outlet; the taper of the ingot mould is fundamental in order to allow the ingot mould to "follow" the shrinkage of the metal consequent to temperature reduction. When the taper of the ingot mould is incorrect, the internal surface of the ingot mould can happen to lose contact with the semi-solid metal (insufficient taper), with an entailed localized reduction of the cooling capacity (in the absence of contact between ingot mould and semi-solid metal, heat transmission decreases remarkably) and therefore with the forming of undesired dishomogeneities in the semi-solid metal, or the internal surface of the ingot mould can happen to press too much on the semi-solid metal (excessive taper) with the entailed onset of undesired strains in the semi-solid metal, worsening the grade of the solidification process.

[0005] To monitor the correct taper of the ingot mould, it has been proposed to use a control instrument that is applied on the outside of a copper plate making up the ingot mould and measures inclination with respect to the vertical of the copper plate itself. However, it was observed that in some situations undesired variations in the taper of the ingot mould can occur, variations that are not detected by known control instruments such as the one described above, which measure inclination with respect to the perpendicular of the copper plates making up the ingot mould. In particular, known control instruments such as the one described above are relatively less reliable when the copper plates are not perfectly planar but have a curvilinear profile.

DESCRIPTION OF THE INVENTION

[0006] The object of the present invention is to provide a control instrument and a method for monitoring a plate of an ingot mould in a continuous casting plant, which control instrument and method be free from the drawbacks described above and, in particular, be easy and inexpensive to carry out.

[0007] According to the present invention there are provided a control instrument and a method for monitoring a plate of an ingot mould in a continuous casting plant, according to what claimed by the annexed claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The present invention will hereinafter be described with reference to the annexed drawings, illustrating a non-limiting exemplary embodiment thereof, wherein:

■ Figure 1 is a schematic view of a continuous casting plant for the making of steel bars;

■ Figure 2 is a schematic perspective view of an upper portion of an ingot mould of the plant of Figure 1;

■ Figure 3 is a side view of an instrument which is manufactured in accordance with the present invention and carries out the monitoring of a plate of the ingot mould of Figure 2; and

■ Figure 4 is a partially sectional front view of the instrument of Figure 3.

PREFERRED EMBODIMENTS OF THE INVENTION

[0009] In Figure 1, a continuous casting plant for the production of steel ingots is globally denoted by 1.

[0010] Plant 1 comprises a ladle 2 feeding molten steel to an underlying tundish 3, from which the molten steel is fed to a vertical solidification path. The vertical solidification path comprises, at the beginning, an ingot mould 4 made of copper, in which primary solidification of steel occurs; downstream of ingot mould 4 made of copper, the vertical solidification path continues with water injectors 5. Plant 1 comprises a station 6 for cutting the steel bars, provided with ejector rolls 7 and a rollover cradle 8 which receives each steel bar from cutting station 6 and feeds the steel bars to an horizontally-conveying roll device 9.

[0011] According to what is illustrated in Figure 2, ingot mould 4 is a tubular body of parallelepiped shape and comprises four copper plates 10 which are cooled by a continuous circulation of cooling water. Each copper plate 10 has a predetermined inclination with respect to the vertical line and/or a specific profile in order to give ingot mould 4 a desired conicity which progressively reduces the cross section of the ingot mould 4 from top to bottom (i.e. from the upper inlet opening, which is larger, to the lower outlet opening, which is narrower). The function of the conicity of ingot mould 4 is that of allowing ingot mould 4 to "follow" the steel dimensional reduction consequent to temperature reduction (i.e. to primary solidification). If the conicity of the ingot mould is incorrect, then the internal surface of ingot mould 4 can lose contact with the semi-solid steel (insufficient conicity), or the internal surface of the ingot mould 4 can press too much on the semi-solid metal (excessive conicity).

[0012] According to what is illustrated in Figures 3 and 4, in order to monitor the correct conicity of ingot mould 4 it used a control instrument 11, which is applied externally to a copper plate 10 which is part of ingot mould 4 and measures both the inclination of copper plate 10 with respect to the vertical line and the vertical profile of copper plate 10 (i.e. the shape of an external vertical wall 12 of copper plate 10 along a vertical line).

[0013] Control instrument 11 comprises a rigid frame 13 having a plurality of feet 14, which are apt to be rested against a vertical wall 12 of plate 10; in particular, frame 13 comprises a beam 15 and a pair of transverse arms 16 , each of which is arranged perpendicularly to beam 15 and supports a pair of feet 14 arranged at opposite sides of beam 15.

[0014] Moreover, control instrument 11 comprises a support device 17, which is fixed to frame 13 and is apt to rest on an upper horizontal wall 18 of plate 10 for supporting frame 13 (i.e. for supporting control instrument 11).

[0015] Support device 17 is shaped in such a way that the weight of control instrument 11 pushes frame 13 against vertical wall 12 of plate 10 when support device 17 rests on upper horizontal wall 18 of plate 10. Thus, it is the weight of control instrument 11 which ensures that feet 4 remain in contact with vertical wall 12 of plate 10, with no need for any further external intervention.

[0016] According to a preferred embodiment, control instrument 11 comprises a box-like body 19 which is fixed to an upper end of frame 13 (i.e. it is head connected to an upper end of beam 13) and is mechanically connected to support device 17 (i.e. support device 17 is not directly connected to frame 13, but is indirectly connected to frame 13 through box-like body 19).

[0017] Control instrument 11 comprises a distance measuring device 20, which oriented towards vertical wall 12 of plate 10 and is apt to measure a distance D from vertical wall 12 (that is, it measures the distance between a reading head of distance measuring device 20 and vertical wall 12).

[0018] According to a possible embodiment, distance measuring device 20 is a laser distance measuring device operating without contact (i.e. the reading head of distance measuring device 20 sends a laser beam against vertical wall 12, and therefore never touches vertical wall 12).

[0019] According to a different embodiment, distance measuring device 20 is a mechanical distance measuring device, operating by contact (i.e. the reading head of distance measuring device 20 continuously touches vertical wall 12).

[0020] Control instrument 11 comprises a moving device 21, which is supported by frame 13 (in particular by beam 15 of frame 13) and supports distance measuring device 20 so as to move distance measuring device 20 along a vertical measuring path P; moreover, control instrument 11 comprises a position sensor 22, which detects the position of distance measuring device 20 along the vertical measuring path P.

[0021] Finally, control instrument 11 comprises a processing unit 23, which cyclically reads distance measuring device 20 and position sensor 22 and correlates the distance D with respect to vertical wall 12 of plate 10 as measured by distance measuring device 20 with the position of distance measuring device 20 along vertical measuring path P as measured by position sensor 22 so as to obtain a profile of vertical wall 12.

[0022] Preferably, processing unit 23 is housed inside box-like body 19 and is connected to a display 24 having the "touch" function and implementing an I/O ("Input/Output") device; i.e. display 24 is used both to show information to the user and to receive instructions from the user.

[0023] According to a possible (but non-binding) embodiment, moving device 21 comprises a slide, which is mounted in a sliding manner along measuring path P and carries distance measuring device 20, a worm screw 25, which is arranged along measuring path P and is mechanically coupled to the slide so as to set the slide in motion when rotated, and an electric motor 26, which is mechanically coupled to an end of screw 25, so as to cause it to rotate. According to a preferred embodiment, electric motor 26 is housed inside box-like body 19. According to a preferred embodiment, position sensor 22 is an angular encoder which is mechanically connected to motor 26 or to screw 25.

[0024] According to an alternative embodiment, not illustrated, worm screw 25 is replaced by a closed-loop belt, tensioned between a motorized upper pulley, which is connected to electric motor 26, and an idle lower pulley; one side of the belt is fixed to the slide carrying distance measuring device 20 and therefore, by moving the belt by means of a rotation of the motorized upper pulley, a corresponding movement of the slide (and therefore of the distance measuring device 20) is obtained along path P.

[0025] According to a preferred embodiment, control instrument 11 comprises a contact sensor 27, which is coupled at least to one foot 14, is connected to processing unit 23 and detects whether or not there is actually a contact of foot 14 with vertical wall 12 of plate 10; processing unit 23 detects the profile of vertical wall 12 of plate 10 only when the contact sensor 27 detects that there is actually a contact of foot 14 with vertical wall 12. Preferably, contact sensor 27 detects the electrical conductivity existing between at least two distinct feet 14 through plate 10; in other words, if the electrical conductivity existing between at least two distinct feet 14 through plate 10 is "high" (i.e. higher than a predetermined threshold value), then an adequate mechanical contact exists between the two feet 14 and plate 10 (which is made of copper, and therefore is an excellent conductor of electricity), whereas if the electrical conductivity existing between at least two distinct feet 14 through plate 10 is "low" (i.e. lower than a predetermined threshold value), then an adequate mechanical contact between the two feet 14 and plate 10 does not exist, and therefore it is not possible to accurately detect the profile of vertical wall 12 of plate 10.

[0026] Control instrument also comprises an inclinometer 28, which is connected to processing unit 23 and detects the angle of inclination of frame 13 with respect to the vertical line (therefore, it detects the angle of inclination of vertical wall 12 of plate 10 with respect to the vertical line) and is preferably housed inside box-like body 19.

[0027] Hereinafter, operation of control instrument 11 for monitoring a plate 10 (or better, a vertical wall 12 of plate 10) of the ingot mould 4 is described.

[0028] Before starting the monitoring, the user couples control instrument 11 to plate 10 by initially resting support device 17 on upper horizontal wall 18 of plate 10, and then letting control instrument 11 "fall" towards vertical wall 12 of plate 10 so that feet 14 rest against vertical wall 12. It is important to observe that handles or other elements apt to be grabbed by the user can be connected to frame 13 and/or to box-like body 19, so as to enable the user to easily manipulate control instrument 11 even remaining at a certain distance from ingot mould 14.

[0029] Once control instrument 11 is coupled to plate 10, the user can start monitoring of plate 10; such a monitoring provides detecting the angle of inclination of vertical wall 12 of plate 10 with respect to the vertical line by means of inclinometer 28, and it further provides obtaining the profile of vertical wall 12 of plate 10 by moving distance measuring device 20 along path P and then correlating, as described above, the distance D with respect to vertical wall 12 of plate 10 as measured by distance measuring device 20 with the position of distance measuring device 20 along vertical measuring path P as measured by position sensor 22.

[0030] Of course, control instrument 11 starts the monitoring of plate 10 only if contact sensor 27 detects that there is actually adequate contact of feet 14 with vertical wall 12 of plate 10.

[0031] Once measuring has been completed, the angle of inclination of vertical wall 12 of plate 10 with respect to the vertical line measured by inclinometer 28 is compared to a predetermined optimal value and, in case of a significant deviation (i.e. a deviation greater than a maximum deviation allowed, which may be expressed in an absolute or relative way) it alerts about the presence of an anomalous situation. Moreover, once measuring has ended, the profile of vertical wall 12 of plate 10 is compared punctually (i.e. point by point) with a predetermined optimal profile and, in case of a significant deviation (i.e. greater than a maximum deviation allowed, which can be expressed in an absolute or relative way) it alerts about the presence of an anomalous situation; e.g., in order to assess the deviation of the measured profile with respect to the predetermined optimal profile, a mean square deviation between the two profiles might be calculated. It is important to note that the above-described comparisons for determining any anomalous situation can be carried out directly by processing unit 23 of control instrument 11, or by a computer receiving (via cable or via radio) the measurements from control instrument 11.

[0032] The above-described control instrument 11 has numerous advantages.

[0033] Firstly, above-described control instrument 11 allows detecting quickly and with extreme accuracy the profile of vertical wall 12 of plate 10; thanks to this detection of the profile, it is possible to detect not only a wrong position of entire plate 10 (wrong position also detected by the measurement of inclinometer 23), but it is also possible to detect any local deformation of plate 10 (i.e. deformations concentrated in a limited zone of plate 10) which can determine local variations of the taper of the ingot mould even in the presence of a correct position of plate 10.

[0034] Moreover, above-described control instrument 11 is of easy and intuitive use also by an inexpert user; in other words, it is possible to profitably use the above-described control instrument even after a simple reading of the instruction manual attached to the control instrument, with no need of specific training.

[0035] Finally, the above-described control instrument is of simple and inexpensive manufacturing.

Claims

1. A control instrument (11) for monitoring a plate (10) of an ingot mould (4) in a continuous casting plant (1); the control instrument (11) comprising:

■ a rigid frame (13) provided with a plurality of feet (14) which are apt to be laid against a vertical wall (12) of the plate (10); and

■ a support device (17), which is fixed with the frame (13) and is apt to rest onto an upper horizontal wall (18) of the plate (10);
the control instrument (11) characterised in that it comprises:

■ a distance measuring device (20), which is apt to be faced towards the vertical wall (12) and is apt to measure a distance (D) from the vertical wall (12);

■ a moving device (21), which is supported by the frame (13) and carries the distance measuring device (20), so as to move the distance measuring device (20) along a vertical measuring path (P);

■ a position sensor (22), which detects the position of the distance measuring device (20) along the vertical measuring path (P); and

■ a processing unit (23), which cyclically reads the distance measuring device (20) and the position sensor (22) and correlates the distance (D) with respect to the vertical wall (12) as measured by the distance measuring device (20) with the position of the distance measuring device (20) along the vertical measuring path (P) as measured by the position sensor (22), so as to obtain a profile of the vertical wall (12).

2. The control instrument (11) according to claim 1, wherein the frame (13) comprises a beam (15), which directly supports the moving device (21), and a pair of transverse arms (16), each of which is arranged perpendicular to the beam (15) and supports a pair of feet (14) arranged at opposite sides of the beam (15).

3. The control instrument (11) according to claim 1 or 2, wherein the support device (17) is shaped in such a way that the weight of the control instrument (11) pushes the frame (13) against the vertical wall (12) of the plate (10) when the support device (17) rests on the upper horizontal wall (18) of the plate (10).

4. The control instrument (11) according to claim 1, 2 or 3, wherein the moving device (21) comprises:

■ a slide, which is mounted in a sliding manner along the measuring path and carries the distance measuring device (20);

■ a worm screw (25), which is arranged along the measuring path (P) and is mechanically coupled to the slide, so as to set the slide in motion when rotated; and

■ a motor (26), which is mechanically coupled to an end of the screw (25), so as to rotate the screw (25).

5. The control instrument (11) according to claim 4, wherein the position sensor (22) is an angular encoder, which is mechanically connected to the motor (26) or to the screw (25).

6. The control instrument (11) according to claim 4 or 5, comprising a box-like body (19), which is fixed to an upper end of the frame (13), houses the motor (26) and the processing unit (23), and is preferably mechanically connected to the support device (17).

7. The control instrument (11) according to one of the claims 1 to 6, comprising a contact sensor (27), which is coupled to at least one foot (14), is connected to the processing unit (23) and detects whether or not there is an actual contact of the foot (14) with the vertical wall (12), the processing unit (23) detecting the profile of the vertical wall (12) only when the contact sensor (27) detects that there is an actual contact of the foot (14) with the vertical wall (12).

8. The control instrument (11) according to claim 7, wherein the contact sensor (27) detects the electrical conductivity existing between at least two distinct feet (14) through the plate (10).

9. The control instrument (11) according to any of claims 1 to 8, comprising an inclinometer (28), which is connected to the processing unit (23) and detects the angle of inclination of the frame (13) with respect to a vertical line.

10. A method for monitoring a plate (10) of an ingot mould (4) in a continuous casting plant (1); the method comprising a step of resting a support device (17) which is fixed to a rigid frame (13) provided with a plurality of feet (14) onto an upper horizontal wall (18) of the plate (10) so that the feet (14) rest against a vertical wall (12) of the plate (10),
the method characterised in that it comprises the further steps of:

■ dispacing, along a vertical measuring path (P), a distance measuring device (20) facing the vertical wall (12) so as to measure a distance (D) with respect to the vertical wall (12);

■ detecting the position of the distance measuring device (20) along the vertical measuring path (P) by means of a position sensor (22); and

■ correlating the distance (D) with respect to the vertical wall (12) as measured by the distance measuring device (20) with the position of the distance measuring device (20) along the vertical measuring path (P) as measured by the position sensor (22) so as to obtain a profile of the vertical wall (12).

Drawing