EP0934786B2 - Process of continuous casting of metal and continuous casting plant for carrying out the method - Google Patents

Description

The invention relates to a method for Continuous casting of metal, in particular steel strands, by pouring the metal into a straight, vertically aligned Mold and subsequent removal of the in the mold formed straight strand, the straight Initially strand along one Transition curve in a circular arc with a radius bent along with a circular arc guide guided to the radius, then in an end straightening zone straightened along a transitional curve and then over an approximately horizontal straight line is carried out, as well as a continuous casting plant for Implementation of the method and a method for Conversion of a continuous casting plant with a curved mold in a continuous casting plant with a straight mold.

It is known, for example, from the AT-B-373 518 and AT-B-331 439, for producing a metal strand in the continuous casting a straight mold to use, i. a mold, whose cavity, in the the liquid metal is poured, just trained and is vertically aligned. The strand is going down the exit from the mold with a guide a roller system, either in sttitzsegmenten or in continuous side members is installed, out and cooled so that the still thin strand shell sufficiently against caused by the ferrostatic pressure Dent supported. At first, mostly the strand below the mold still by means of a straight guide guided, which extends over a length, the strand due to the direct cooling below the mold secures a sufficiently strong strand shell, so that the strand then in a bending zone such can be bent that he along a circular arc guide, which connects to the bending zone and a has predetermined radius, further promoted can be. At the circular arc guide closes one End straightening zone, in which the strand again straightened becomes. In the straight state, the strand is over an approximately horizontally oriented straight guide ausfördert.

It is also known, for example from the AT-B - 249 896, for producing a metal strand in the Continuous casting process while avoiding a bending zone To cast the strand already arcuate, namely in a so-called curved mold. In such a Arched mold is the cavity into which the liquid metal is poured, arcuate, preferably circular arc formed so that the emerging from the mold Strand immediately after emergence by means of a Circular arc guide supported and promoted can. In this case, only at the end of the circular arc guide to arrange an end straightening zone in which the Strand is again straightened, so that he subsequently as described above on an approximately horizontal arranged straight guide be discharged can.

Continuous casting plants with curved molds were although built worldwide; However, these plants have metallurgical Disadvantages, which are mainly seen in that with the pouring stream introduced impurities and gas bubbles that go deep into the liquid core of the Stranges penetrate, not so easy to Gießspiegel can ascend like a straight Mold. Also, the flow conditions at a Bogenkokille less favorable, so that it tends to disturbances can come with cup growth.

For these reasons, one has tried Continuous casting plants with curved molds in continuous casting plants to rebuild with a straight mold. Will you Use the same strand guide as you do at the original continuous caster with curved mold was provided, one is forced to the circular arc Strand guide vorzuordnen a bending zone and above it one straight line To arrange continuous casting mold. However, there is Difficulties, because then the level of the straight mold far above the height of the originally intended Arched mold lies. This is not acceptable as under Circumstances not only the casting hall can be enlarged must, but redesigned the entire hall concept must be, because it must the casting platform, intermediate vessels and the pan tower and the feeder the pans etc. adapted to the new level become. The result is a complete transformation the casting hall, which is accordingly expensive and on the other hand, a long shutdown of the casting operation conditional.

Another option is the circular arc guide to replace, u.zw. through a circular arc guide, suitable for straight mold with downstream Bending zone. However, this is also very expensive and costly, so that in most cases the metallurgical disadvantages of a curved mold in Buy has taken.

The invention has as its object, a method for continuous casting and a continuous casting plant to provide for the implementation of the procedure in which the strand using a straight mold and using the most important components a continuous casting machine with a bent mold such as e.g. the circular arc guide, casting platform, etc. are poured can. Another object of the invention is in a Continuous casting plant with straight mold about the height To comply with a continuous caster with gebegener Mold at the same radius of the cast strand or the circular arc guide has. Necessary conversions when changing from a curved mold to a straight chillers should be minimized in terms of time and cost become.

The task is in a method for Continuous casting of a metal strand of the type described above Art solved by the strand in at least a bending zone along a transitional curve in a circular radius shape having a first radius is bent and in at least one subordinate a plurality of rewind force applying rollers comprising straightening zone along a transition curve in one Circular arc shape with a larger radius than the radius, which has the strand after the first bending zone, bent is, with the larger radius preferably the radius of the circular arc guide in front of the end straightening zone equivalent.

Preferably, the first radius having strand between the first bending zone and the first downstream straightening zone along a Circular arc guide guided with this first radius, wherein advantageously emerging from the mold just Strand between the mold and the first bending zone is guided along a vertical linear guide.

Is the radius of the circular arc guide very big, will suitably the strand after bending in the first of the bending zone downstream straightening zone in at least one further downstream straightening zone in a circular arc shape with a larger radius than the Radius the strand before the downstream straightening zone has bent.

For large radii of the circular arc guide can according to a variant on the strand after deformation in the first bending and downstream straightening zone at least one more deformation in another Bending and downstream straightening zone carried out become.

A continuous casting plant for carrying out the inventive method with a straight mold, one of these downstream in Strandausziehrichtung Strand guide with a bending zone, a circular arc guide and an end straightening zone followed by approximately horizontal linear guidance is characterized that at least one bending zone at least a plurality of rewinding force applying rollers comprehensive (s) straightening zone with subsequent circular arc guide is subordinate.

It is advantageous between the first bending zone and the first straightening zone provided a circular arc guide, being expedient between the mold and the first bending zone a vertical straight line for the strand is provided.

According to a variant, after the first bending and subordinate straightening zone at least one further bending zone provided with downstream straightening zone.

A preferred embodiment is characterized characterized in that according to AT-B - 331 439 of caused by the bending zone (s) or straightening zones Course of stretching of the strand in at least one the two transitional areas approximately the shape of a skewed distorted, having a Wendetangente "S" possesses, whereby the slope at the beginning and at the End of the stretch curve applied over the area Zero is related to the X axis of a Cartesian Coordinate system whose origin is in each case located at the beginning of the transition curve and its X-axis represents a tangent to the transition curve.

This corresponds expediently the slope the turning tangent at most a maximum allowable Change in elongation of 0.0025% / mm at Bending and 0.0030% / mm when straightening.

The transition curve preferably follows the differential equation of the change in curvature (y "') y '''=φ' (x j ) · 1 R e 0 X e ∫φ '(x j dx) and φ '(x _j ) is the function of strain change over the extent of the bending or straightening zone has a first rising from zero, then reaching the maximum of the strain change and then falling back to zero gradient, R _{E is} equal to the circular arc radius at the end of the bending or at the beginning of the straightening zone and X _{E is} the vertical projection of the bending zone or the horizontal projection of the straightening zone, and x _{j is} a position coordinate in the coordinate system.

• daß die Bogenkokille und ein daran anschließender Teil der Kreisbogenführung entfernt werden,
• daß eine gerade Kokille an einer Stelle der Stranggießanlage eingebaut wird, deren Entfernung zum Krümmungsmittelpunkt der Kreisbogenführung geringer ist als der Radius der ursprünglichen Kreisbogenführung,
• daß eine eine Übergangskurve aufweisende Biegezone fluchtend zur geraden Kokille eingebaut wird, aus der der Strang mit einem ersten Radius, der geringer ist als der Radius der Kreisbogenführung, austritt, und
• daß der Biegezone nachfolgend mindestens eine mehrere eine Rückbiegekraft aufbringende Rollen umfassende(n), Richtzone eingebaut wird, aus der der Strang mit einem zweiten Radius, der größer ist als der erste Radius, austritt, und welcher zweite Radius vorzugsweise dem Radius des in der Stranggießanlage verbleibenden Teils der ursprünglich vorhandenen Kreisbogenführung entspricht und in diese Kreisbogenführung fluchtend, d.h. tangentengleich übergeht.

A method for converting a continuous casting plant with a curved mold, a subsequent circular arc guide and an end straightening zone with downstream approximately horizontal straight line in a continuous casting with a straight, vertically oriented mold is characterized in that

• that the arched mold and an adjoining part of the circular sheet guide are removed,
• that a straight mold is installed at a position of the continuous casting plant whose distance to the center of curvature of the circular arc guide is less than the radius of the original circular arc guide,
• that a bending zone having a transition curve is installed in alignment with the straight mold, from which the strand emerges with a first radius which is less than the radius of the circular arc guide, and
• in that the bending zone is subsequently fitted with at least one reel straightening roller comprising a plurality of rewinding force rollers from which the strand exits at a second radius greater than the first radius and which second radius is preferably at the radius of the continuous casting line Remaining part of the original circular arc guide corresponds and in this circular arc guide in alignment, ie tangent equal.

It is useful between the bending zone and the first straightening zone incorporated a circular arc guide.

According to a preferred variant is between the mold and the bending zone is aligned with the Molded linear guide installed.

To avoid too much bending of the Strangers to find the Auslangen, will be beneficial to the just mold in a level in the continuous caster built in, that of the level of the bow mold only slightly deviates, preferably low above this level lies, with the deviation from the level of the curved mold depends on the height of the hall, the installed Crane system etc. As "low height deviation" is usually designated one in which a Conversion of the hall construction avoided in any case can be; usually the height deviation lies in custom-designed casting halls at ½ m to maximum a meter.

For large radii the circular arc guide has it proved to be expedient if subsequently to the first straightening zone another straightening zone with downstream Circular arc guide is installed.

After another variant it is for big Radii of circular arc guide appropriate if after the first bending and downstream straightening zone at least one more bending and subordinate one Richtzone is installed.

The invention is described below with reference to a Embodiment, which illustrates in the drawing is explained in more detail, wherein the Fig. A schematic Side view of a continuous caster with straight Mold and curved mold shows.

In the figure is a curved mold with dashed lines 1 with the adjoining strand guide 2 illustrates, for simplicity of the Representation of the strand guide 2 in the upper area - d. H. immediately below the arched mold 1 - only by a dashed line representing the strand outer and underside, respectively illustrated is shown. This strand guide 2 is, as usual, of adjoining the mold Support and guide rollers 2 'formed, the Strand on both sides, so on the outside or bottom and also on the inner or top at close intervals support. The illustrated with dotted line Strand or sub. Strand outside thus forms a Enveloping all these roles.

The casting platform 3 is located approximately at the level of the upper edge of the curved mold 1. The interior 4 of the curved mold 1, ie the continuous cavity 4, in which the molten metal, via a conventional ladle, not shown, in a likewise not shown, but conventionally ausgestaltetes intermediate vessel and flows from this via a pouring tube in the curved mold 1, is designed arcuate, u.zw. a circular arc. The subsequent to the curved mold 1 circular arc guide 2 has a radius R _end . The center 5 of this circular arc guide is located approximately at the level of the lower half of the curved mold 1 and thus by the height H ₀ below the mold level 6 of the curved mold first

To the circular arc guide 2, which is not extends over a quarter of a circle, one closes Straightening zone 7, in which the strand by means of support and Bending rolls is straightened. The straightening zone 7 has advantageously a transition curve according to AT-B - 331 439 on to a gentle straightening of the strand too to back up. After the straightening zone 7 is an approximately horizontally oriented straight guide 8 is provided, the likewise closely adjacent support and guide rollers having. Along this linear guide 8 is the Extruded strand, then into individual strand pieces separated or also directly verwalzt. The straight line guide 8 may also deviate from the horizontal; so 5 ° ± from the horizontal are easily possible.

With full lines is in the Fig. One Continuous casting shown, in place of the curved mold 1 a straight mold 9 is used. As can be seen from the figure, this straight mold 9 by a horizontal amount HH relative to the arched mold 1 in the direction of the center 5 of the circular arc guide 2 arranged offset.

In addition, this straight mold 9 is offset by a small amount in terms of height relative to the curved mold 1, u.zw. raised by the height H _v . To the straight mold 9, ie a mold 9 with a vertically aligned and rectilinear cavity 10, in which the molten metal is poured, closes. a vertically oriented straight guide 11 at. This ensures a purely vertically oriented portion of the cast strand which ensures efficient cleaning, ie rising of contaminants and gas bubbles, which are flushed into the liquid core of the strand with the pouring stream.

Following the vertical straight line 11, a bending zone 12 is provided which has a transition curve along which the strand of straight is bent into a circular arc shape. This transitional curve is suitably also according to AT-B - 331 439 designed.

The circular arc shape has a radius R _min , which is less than the radius R _{end of} the circular arc guide 2, which was provided for the curved mold 1. Downstream of the bending zone 12 is a circular arc guide 13 with the radius R _min , which extends only over a smaller radius angle of about 20 °. At this circular arc guide 13 includes a straightening zone 14, in which the strand is slightly directed, u.zw. exactly on the radius R _{end is} bent, the originally provided for the curved mold 1 circular arc guide 2 has. R _min is to be selected depending on the material to be cast, the casting speed and the casting thickness (strand thickness). When choosing R _min , it should be noted that the strand shell is not exposed to excessive loads (not too large a change in strain) during initial bending.

The closer the mold 9 is moved to the center of curvature 5, the sooner it is possible to maintain a level 3 of the arc mold 1 for the straight mold 9, despite a relatively long linear guide 11, but with a reduction of R _min , especially if one long vertical straight line 11 is desired.

In this way succeeds the strand from a straight mold 9 in the circular arc guide. 2 to bring the Bogenkokille 1 without the right mold 9 must be raised far. Thus it succeeds with only a minor conversion - it only needs the first part 15 of the circular arc guide 2, by the Bogenkokille 1 goes out and until the end of the newly built Straightening zone 14 extends, be removed - itself all metallurgical advantages of the straight mold to take advantage of. The tundish and the pancake tower can be used without further ado possibly after only a slight increase. The casting hall itself is by no means affected.

From the Fig. It can be seen that a slight Shortening the subsequent to the mold 9 vertical straight line 11 would suffice, and the just mold 9 would be exactly on the level to stand on which the curved mold 1 was located Has.

Essential to the invention is that the emerging from the straight mold 9 strand initially bent to a radius R _min we, which is smaller than the radius R _{end of} the circular arc guide 2 of the arc mold 1, and only then on this radius R _{end is} bent. This bending of the straight strand on the radius R _end can also take place in several stages, for example by arranging several straightening zones 14 in succession, but also by bending in a first bending zone 12, which bends the straight strand to a narrower radius R _min than the radius R _{end of} the circular arc guide, then directing to a radius slightly greater than R _min , which the strand occupies when he leaves the first bending zone, this process can also be repeated several times, until the radius R _{end of} the circular arc guide of the arc mold is reached , These variants with multiple straightening or repeated bending-straightening are advantageous to apply, if it is desired that the straight mold 9 is located exactly on the level 3 of the developed curved mold 1.

Claims (18)

1. A process for continuously casting metal strands, in particular steel strands, by casting the metal into a straight, vertically oriented mold (9) and subsequently drawing off the straight strand formed in the mold (9), wherein the straight strand along a transition curve at first is bent into a circular arc shape having a radius (R_end), is guided along a circular arc guide (2) having said radius (R_end), subsequently is straightened in a final straightening zone (7) along a transition curve and, after this, is extracted via an approximately horizontal straight guide (8), characterized in that the strand in at least one bending zone (12) along a transition curve is bent into a circular arc shape having a first radius (R_min) and in at least one consecutively arranged straightening zone (14) comprising several rolls applying a reverse-bending force (n) is bent, along a transition curve, into a circular arc shape having a larger radius (R_end) than the radius (R_min) of the strand after the first bending zone, the larger radius (R_end) preferably corresponding to the radius (R_end) of the cricular arc guide (2) in front of the final straightening zone (7).
2. A process according to claim 1, characterized in that the strand having a first radius (R_min) between the first bending zone (12) and the first consecutively arranged straightening zone (14) is guided along a circular arc guide (13) having said first radius (R_min).
3. A process according to claim 1 or 2, characterized in that the straight strand emerging from the mold (9) is guided between the mold (9) and the first bending zone (12) along a vertical straight guide (11).
4. A process according to one or several of claims 1 to 3, characterized in that the strand, after having been bent in the first straightening zone (14) following the bending zone (12), in at least one further consecutively arranged straightening zone is bent into a circular arc shape having a larger radius than the radius (R_min) of the strand in front of the consecutively arranged straightening zone.
5. A process according to one or several of claims 1 to 4, characterized in that at least a further shaping of the strand is effected in a further bending zone and consecutively arranged straightening zone, following shaping in the first bending zone and consecutively arranged straightening zone (12, 14).
6. A continuous casting apparatus for carrying out the process according to one or several of claims 1 to 5, comprising a straight mold (9), a strand guide following upon said mold in the strand extraction direction and including a bending zone (12), a circular arc guide (2) and a final straightening zone (7) followed by a consecutively arranged, approximately horizontal straight guide (8), characterized in that at least one straightening zone (14) comprising several rolls applying a reverse-bending force (n) and followed by a consecutively arranged circular arc guide (2) is arranged to follow at least one bending zone (12).
7. A continuous casting apparatus according to claim 6, characterized in that a circular arc guide (13) is provided between the first bending zone (12) and the first straightening zone (14).
8. A continuous casting apparatus according to claim 6 or 7, characterized in that a vertical straight guide (11) is provided for the strand between the mold (9) and the first bending zone (12).
9. A continuous casting apparatus according to one or several of claims 6 to 8, characterized in that at least one further bending zone followed by a straightening zone is arranged to follow the first bending zone and consecutively arranged straightening zone (12, 14).
10. A continuous casting apparatus according to one or several of claims 6 to 9, characterized in that the strand elongation course caused by the bending zone(s) (12) and straightening zones (7, 14), respectively, in at least one of the two transitional regions approximately has the shape of an obliquely distorted "S" including an inflectional tangent, wherein the slopes at the beginning and end of the elongation curve plotted above said region are zero, based on the X axis of a cartesian coordinate system whose origin is each located in the beginning of the transition curve and whose X axis constitutes a tangent to the transition curve.
11. A continuous casting apparatus according to claim 10, characterized in that the inclination of the inflectional tangent at most corresponds to a maximally admissible change of elongation of 0.0025 %/mm during bending and 0.0030 %/mm during straightening.
12. A continuous casting apparatus according to claim 10 or 11, characterized in that the transition curve follows the differential equation of the change of curvature (y''') y''' = ϕ'(xj)·1REoXE∫ϕ'(xj)dx and ϕ' (x_j) is the function of the change of elongation, which, over the extension of the bending and straightening zones (12, 14, 7), has a course initially rising from zero, then reaching the maximum of the change of elongation and then dropping back to zero, R_E is the radius of the circular arc at the end of the bending zone or beginning of the straightening zone (12, 14, 7), respectively, and X_E is the vertical projection of the bending zone (12) or the horizontal projection of the straightening zone (14, 7), respectively, and x_j represents a position coordinate within the coordinate system.
13. A process for converting a continuous casting apparatus including a curved mold (1), a circular arc guide (2) following thereupon and a final straightening zone (7) with a consecutively arranged, approximately horizontal straight guide (8), into a continuous casting apparatus including a straight vertically oriented mold (9), characterized in that

    the curved mold (1) and a circular arc guide (2) part (15) following thereupon are removed,

    a straight mold (9) is installed on a continuous casting apparatus site whose center line distance relative to the center of curvature (5) of the circular arc guide (2) is smaller than the radius (R_end) of the original circular arc guide (2),

    a bending zone (12) including a transition curve is installed in alignment with the straight mold (9), from which bending zone the strand having a first radius (R_min) smaller than the radius (R_end) of the circular arc guide (2) emerges, and

    at least one straightening zone (14) comprising several rolls applying a reverse-bending force (n) is installed to follow the bending zone (12), from which straightening zone the strand having a second radius (R_end) larger than the first radius (R_min) emerges, which second radius (R_end) preferably corresponds to the radius (R_end) of the part of the originally present circular arc guide (2) remaining in the continuous casting apparatus and merges into this circular arc guide (2) in an aligned, i.e., tangentially equal manner.
14. A process according to claim 13, characterized in that a circular arc guide (13) is installed between the bending zone (12) and the first straightening zone (14).
15. A process according to claim 13 or 14, characterized in that a straight guide (11) registering with the mold (9) is installed between the mold (9) and the bending zone (12).
16. A process according to one or several of claims 13 to 15, characterized in that the straight mold (9) is installed into the continous casting apparatus on a level only slightly deviating from the level (3) of the curved mold (1), preferably lying closely above said level (3).
17. A process according to one or several of claims 13 to 16, characterized in that a further straightening zone with a consecutive circular arc guide is installed so as to follow the first straightening zone (14).
18. A process according to one or several of claims I 1 to 17, characterized in that at least one further bending zone with a consecutive straightening zone is installed so as to follow the first bending zone and consecutively arranged straightening zone (12, 14).

Images