DE1558185A1 - Method and device for the continuous casting of steel - Google Patents

Description

CONCAST INCORPORATED HBW YORK (U.S.A.)

Method and device for continuous glazing of steel

The present invention relates to a method for the continuous casting of steel, in which molten Steel is continuously fed into one end of a mold and from the other end of the mold is continuously drawn as a partially solidified strand, and a device for carrying out the

In the conventional continuous casting process molten metal poured into a permanent mold. These cools the edge zone of the metal and causes it to solidify, so that a strand is formed which is continuously drawn from the mold, while also continuously, according to the speed of the drawn strand, molten metal is poured into the mold. After leaving the mold

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the strand is further cooled, for example by spraying water. This cooling of the strand in After leaving the mold, secondary cooling is used to achieve complete solidification of the strand.

In most continuous casting plants, the mold axis is arranged vertically and the strand leaves the mold in a vertically downward direction. After its complete solidification it will be cut off pieces of the desired length from the strand. Since the strand naturally solidifies completely at the interface must be, the casting speed in such systems depends on the height and is therefore economical Reasons are often limited. This means that the casting speed is required in such systems upward to limit the strand to completely solidify within reasonable vertical dimensions between the mold and the cutting device. The costs of the system would increase for higher casting speeds exceed an economic level.

In the continuous casting of steel, these problems are due to the high temperature of the liquid steel and the long duration up to the complete solidification of the strand is particularly great. For example, in normal systems

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^: ·, - ■ ■ · ^: 3 V ■ ■,. ■; ■■ ■■■■. '"For the continuous casting of. Steel Distances of 21 meters between the mold and the cutting unit are not uncommon and even these distances require one upper limit of the casting speed to a value that is lower than the theoretically possible speed.

In order to reduce the height of the system, it is known to cast the strand in a mold with a vertical axis and to cool the strand emerging from the mold further in a secondary cooling zone also arranged vertically and to guide it through rollers. The strand is then bent horizontally in a bending device. In such systems, the strand is curved at an angle of approximately 90 °, so that the curved strand is tangent to a horizontal line. At the point of contact of the tangent, the strand is straightened and then guided in the horizontal direction to a cutting device. Such systems enable the required overall height of the system to be reduced. However, this solution is not entirely satisfactory to the extent that, understandably, a rather large radius of curvature for the bend. of the strand is required. Even with very large radii of curvature, the bending and subsequent straightening of the solidified strand without hardening cracks and without other damage to it is associated with considerable difficulties »
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It is also known to pull the strand from a vertically arranged mold, the axis of which is curved is. In such a mold, the strand is already cast with a curvature and after it emerges in turn cooled from the mold by spraying water in a secondary cooling zone. Inside the secondary cooling zone the strand is guided by rollers or rollers in such a way that that its curvature is maintained. When it reaches the horizontal, the strand becomes in a Straightening device straightened by further rollers or cylinders and fed to a cutting unit. This arrangement undoubtedly allows a further reduction in the required overall height of the system. Here too, however relatively large radii of curvature required, which has an unfavorable effect on the overall height.

While the constructions described undoubtedly result in a reduction in the required overall height of a However, even with such systems, the possible casting speeds are limited. In addition comes that the use of support and bending rollers in the secondary cooling zone immediately after the Mold poses problems. Within this zone and especially immediately after the mold, the crust is very thin and the hydrostatic pressure of the molten metal is very thin

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.-Inside this crust causes a bulging of the Crust in the spaces between successive rollers. This successive bulging and indentation of the crust can cause it to break and thus lead to leakage of liquid metal. At best, however, surface cracks will arise.

Since the beginning of the development of continuous casting, casting appeared in a horizontally arranged manner Permanent mold as desirable, It was recognized that this in addition to a maximum reduction in the required overall height, also an optimal direction of movement of the cast Strand for the needs of secondary cooling, separating and further processing would result. At a horizontally running strand loses its distance between the mold and the cutting unit, for example Significance, as there is enough for this in most systems

Floor space can be provided. The horizontal Continuous casting allowed, with a maximum casting speed to work and the distance between the mold and Adapt the cutting unit to the requirements.

-Horizontal molds have so far been used in continuous casting of aluminum has been used in plants in which the liquid aluminum is replaced by a refractory Nozzle inserted into one end of a horizontal mold

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will lead. When casting aluminum, the pouring spout is not wetted by the liquid aluminum and remains clean during the casting process. When casting steel, however, and especially when using it an oscillating mold, this method falls with a horizontal mold ^ and fixed in it Casting spouts out of consideration. It turned out that the liquid steel wets the pouring nozzle and at the exit this neck solidified. The steel solidified in this way tends to be tubular through the entire mold to grow through it, so that finally at the exit end liquid metal escapes from the mold.

The invention is based on the task of obtaining a method for the »continuous casting of steel which with a minimum height of the system oino large possible Casting speed allows at the same time optimal. Direction of movement of the cast strand.

According to the invention, this object is achieved in that the molten metal in the mold is cooled to a surface temperature of between 1372 ° C and 1095 ° C when it leaves the mold, forming a solidified land zone and the strand is passed through a guide, which is initially curved and then directed again and at the same time on one

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Surface porosity between 1095 ° C and 700 ° C at Leaving this guide is chilled, and that on top of that the directed, partially solidified strand, passed through a secondary cooling zone and in this up to complete solidification is cooled.

The device for carrying out the method is characterized by an open at both ends, the strand forming a thin, solidified Edge zone cooling mold, through a guide for the Strand between the mold and a secondary cooling clay, which guide at the entry and exit ends straight section and between these straight sections has a curved section, so that a through Strand first curved and then straightened again; is maintained by coolant the thin solidified edge zone of the through this guide running cord, through organs to support the cord as it passes through the secondary cooling zone and through Organs for the direct application of coolant to the Strand in the secondary cooling zone to complete the solidification of the strand. . ■

When using a mold, its axis

is inclined to the horizontal that liquid metal can be poured into its upper open end, the

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Direction of the partially solidified strand after exiting the mold changed so that it was in a horizontal position Direction of a horizontally arranged secondary cooling zone can be fed. It is not necessarily so required to feed the strand exactly horizontally. The advantages of the invention can also be found in Plants are realized in which it appears desirable for structural or other reasons, the line in in a direction slightly inclined to the horizontal.

According to your method according to the invention liquid steel with a temperature of around 1650 C. continuously poured into the open upper end of a mold, the axis of which is inclined to the horizontal. As hitherto the mold wall has preferably been made of a metal with high thermal conductivity, e.g. copper and the primary cooling in the mold is carried out by a circulating liquid, for example cold water.

The mold cavity can be of any cross-section, for example circular, square or rectangular.

During the casting process, the liquid metal in the mold is removed by heat extraction through the mold

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wall with the formation of a thin solidified edge-ζοηβ cooled ,, The heat extraction is dependent controlled by the casting speed, for example by setting the circulation speed accordingly of the mold coolant, in such a way that ■ Jass the surface temperature when leaving the Strand from the mold lies between 1372 ° C and 1095 ° C. ;

The partially solidified strand emerging from the mold is then passed through a guide, in which egg first bent and then again is judged. The direction of movement of the strand is changed so that the strand is fed to an essentially horizontally arranged cooling zone, in which it is further cooled until it completely solidifies will.

This tour can go through * a number of Be formed guide elements which are provided with surfaces which bear against the strand and this support and which are arranged so that they have a curved Form the guideway for the strand. When the strand enters the curved guide part it is curved and directed when leaving the curved guide part. The mentioned guide elements are like this

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designed so that they can accommodate a circulating coolant. In addition, sio can be trained in this way be that small amounts of coolant are directed through their walls directly onto the strand, around the Lubricate the guide and facilitate bending and movement of the strand through this guide.

During the movement of the strand through this guide it is important that the thin crust, which was formed in the mold is maintained and its re-melting through heat absorption from the swamp, on the other hand it is just as essential that the thickness of the crust during the passage through this guide does not increase significantly in order to avoid the bending and then straightening of the Allow strand without damage.

While it is thus necessary to cool the strand while it passes through the guide to the To maintain thin crust, it is also desirable to have this cooling effect within the aforementioned guide to be limited to the minimum required. For this purpose, the heat extraction is controlled by the Coolant circulation or otherwise regulated in such a way that the outer surface of the crust when it leaves the

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called leadership has a temperature between 1095 ° C and 700 ⁰ C.

After leaving the said guided tour will be the strand is passed through a secondary cooling zone, in which it is cooled down to its complete solidification will.

As it passes through the secondary cooling zone the strand is guided in a straightened state until it has completely solidified. For example the strand can be moved from below through a row of rollers arranged at short distances from one another be supported whose axes lie in a common plane. When leaving the mentioned tour, the Strand taken up by these rollers or by other support elements and on this one with further cooling Cutting unit fed.

The cooling in the secondary cooling zone is preferably carried out by the direct application of coolant onto the surfaces of the strand, for example by spraying water. .

The strand is drawn out by drive rollers, which convey the whole strand from the mold through the said guide and through the secondary cooling zone.

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Since the distance from the mold to the secondary cooling zone is very small, the necessary Extraction forces are also low and the extraction rollers can be arranged at the beginning of the secondary cooling zone nevertheless · at this point the crust is still thin is.

Further features of the subject matter of the invention emerge from the following description of an exemplary embodiment, which is explained in more detail by means of figures. It shows:

1 shows a side view of a continuous casting plant, FIG. 2 shows a section through part of the Plant according to Fig. 1,

Fig. 3 is a section along the line III-III of Figure 2 ,, and

Fig. 4 shows a section through the mold with inserted Cold strand at the start of casting.

The device shown in the figures comprises a mold 10, which via an intermediate container or tundish 12 and a pouring nozzle 14 liquid steel is fed. The mold is water-cooled and the mold cavity is delimited in a known manner by means of copper plates 11 which are in direct contact with the liquid metal and a rapid heat

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ensure withdrawal. As a result, the edge zone of the liquid metal solidifies and forms a thin crust 13 which delimits the strand continuously drawn from the mold. If necessary, the mold can be oscillated along its axis in a known manner. After exiting the mold, the strand is guided in a guide consisting of several elements 15I ₁ 152, 153, 154, 155 and 156. The device shown is used for the continuous casting of slabs 16. Each element of the guide comprises an upper plate 17 and a lower plate 18, which are held at a certain distance from one another by suitable means. The plates 17, 18 are hollow and are cooled by circulating water which circulates in the cavity 20 via inlet and outlet lines 21. Further cooling takes place through a small proportion of cooling water which reaches the surface of the strand directly through openings 22 in the surfaces of the plates 17 and 18 which are in contact with the strand. The openings 22 are in communication with the cavities of the. Plates and the pressure prevailing there are selected in such a way that water is pressed out of the openings 22. The coolant acting directly on the strand in this catfish serves to lubricate the guide and facilitate the movement of the strand in this guide.

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As can be seen from the figures, the elements 151 and 152 follow the guide immediately The mold is straight, elements 153, 154 and 155 are curved and element 156 is straight again. When traversing the strand from element 151 to element it is slightly curved and then assumes the curvature of the element 153. This curvature becomes 1 for the pass of the strand is maintained by elements 154 and 155 so that the direction of movement of the strand of the direction when leaving the mold is changed to a substantially horizontal direction. When walking through of the strand from element 155 into element 156, it is directed so that it is the latter element straightened leaves.

The first element 151 is advantageous and not curved to avoid the risk of breaking the thin otrangkrust, which was formed in the mold, to counteract and a certain stabilization of the temperature before the strand is bent. For this purpose, the plates 23 of the adjacent to the strand Elements 151 advantageously made of copper. In contrast, the plates in contact with the strand are the Elements 152, 153, 154, 155 and 156 are advantageously made of cast iron.

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Element 152 is straight and not curved. As the strand is curved by member 153, practice

it exerts a reaction force against the side walls of the immediately preceding element 153. Even though element 151 could precede element 153 in some cases, it is advantageous if the reaction forces mentioned are prevented from acting against the relatively soft copper plates of element 151. For this reason the element 152 is provided with plates made of cast iron. This prevents the reaction forces resulting from the bending from acting on the soft copper plates. The radius of curvature of the guide is advantageously chosen to be so large that the stretching of the crust on the outside of the curvature that occurs when the strand is bent and subsequently straightened does not exceed a value of 1 to 2 ½%. Accordingly, a radius of curvature of about 10 meters is selected for a 30.5 cm thick slab, for example.

When the strand passes through the guide sections 151 to 156, the circulation of the coolant carefully controlled in such a way that · the thickness of the Crust is always sufficient to rule out breakthroughs at the points of curvature, but the thickness of the crust at the point where it is judged, not a judging

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complicating and the formation of surface cracks favoring degree exceeds.

For this purpose, the cooling is controlled in the range of the strand of the elements 151 to 156 in such a way that the strand as it leaves the element 156 has a temperature that is not more than 1O95 ° C and not less than 700 ⁰ C.

In elements 151, 152 and 156, the side walls of the string are supported by side plates 24 and led. These are also hollow and water-cooled in accordance with the plates 17 and 18. In the curved elements 153, 154 and 155 advantageously become the side walls of the string through a row guided by wedge-shaped rollers 25 which are rotatably mounted on axles, their imaginary extensions go through the center of curvature of the curved guide portion. In the drawing is for each of the Elements 153, 154 and 155 only show a pair of such wedge-shaped rollers, but several could of course be used Pairs per item can be provided.

The individual guide sections are preferably designed so that they can be used for repairs and replacements are easily accessible, as can be seen in detail from FIG. The lower plate 18 is supported by a frame 30

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carried. By means of cross members or webs 32, the required Strength achieved. The upper plate 17 is mounted in a frame 33 which has a Pin 34 is hinged to frame 30. The attachment takes place via a bolt 35 and a nut 36. One Axis 37 of the wedge-shaped rollers 25 is in a frame 38 held, which is slidable relative to the frame 30. The rollers are preferably water cooled in a known manner. The conicity of the outer roller surfaces, as well as the Inclination of the roller axes in the curved guide section ensure that the side walls of the strand are guided without damaging the thin strand crust.

A number of factors enable ongoing Curvature and the subsequent straightening of the Strand without the risk of breakthroughs or other damage. First and foremost, the radius of curvature of the curved guide sections can be chosen so large that that the strand is only slightly bent. Next lets The thin crust in the guide can be bent and straightened slightly at the specified temperatures. Furthermore, since the vertical distance between the mirror of the liquid Metal in the mold and the. Axis of the strand on the The place where it leaves the guide is kept relatively small is the ferrostatic pressure in the strand

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much smaller than with the previous continuous casting plants. For example, in the illustrated Device, with a radius of curvature of the curved guide section of approx. 10 meters, the distance between the level of the liquid metal in the mold and the strand axis when leaving the element 155 be less than 1.5 meters. At this distance the ferrostatic pressure is about 0.85 at compared with pressures of 70 at, which is the case with vertical continuous casters are common. The low ferrostatic pressures can be more easily absorbed by the thin crust and the risk of breakthroughs when bending and straightening the strand »is considerably lower.

Upon exiting the element 156, the strand passes between a series of rotatable pairs of rollers Drive rollers 42 are arranged in a substantially horizontal plane and guide the strand during its Passing through the secondary cooling zone. In the secondary cooling zone, the strand undergoes intensive cooling Water jets 43 thrown directly against his Surface can be straightened.

Pouring liquid steel into an inclined mold is particularly important at the start of the casting process take certain precautionary measures to avoid damaging the

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to avoid copper mold surfaces. Such damage can by using a cold pipe according to Figure 4 be avoided.

In FIG. 4, a tundish 12 is shown, to which a pouring nozzle 14 is articulated, through which liquid steel is poured into the mold 10. Before the start of the casting process, a cold strand is introduced which has a cold strand head 56 at its end. This head is provided with a recess 58 into which molten metal flows and ^y solidifies to ensure the end of the link to be cast strand with the dummy bar to, and take off. The cold strand head corresponds exactly to the dimensions of the strand to be produced and is usually dressed with an asbestos seal 60, for example by an asbestos cord inserted into a V-shaped groove. An arm 62 of the cold strand head extends beyond the lower end of the pouring spout 14. During casting, the liquid metal hits the arm 62. This protects the plates 11 of the mold from erosion by the hot molten steel. As soon as the mold is filled to the level of the metal level 69, the molten steel forms a cushion that prevents the inflowing liquid steel from directly impacting the mold plates delimiting the mold cavity. In many cases

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it may be desirable to use a lubricant on the Apply mold inner surfaces. Such can be introduced through line 66.

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Claims (12)

PATENT CLAIMS 1. Process for the continuous casting of steel, at which molten steel continuously into the one Inserted the end of a mold and from the other end of the Continuous mold as a partially solidified strand is drawn, characterized in that the molten metal in the mold solidified to form a Edge zone to a surface temperature when leaving the mold is cooled between 1372 ° C and 1095 ° C, and the strand passed through a guide, first curved in this and then straightened again and at the same time to a surface temperature between 1095 ° C and 700 ° C is cooled when leaving this guide, and that on this the directed, partially solidified strand passed through a secondary cooling zone and in this up is cooled to complete solidification. 2. The method according to claim 1, characterized in that that the mold axis is inclined to the horizontal and the directed, partially solidified strand emerges from the guide in a substantially horizontal direction and is passed through the secondary cooling zone. ; ";. · - 21 ■ - ■.; ■ 009812 / Q682 3. The method according to claim 1, characterized in that the mold axis is straight and the Strand in the mentioned guide first along a straight line, then along a curved line and then is again guided along a straight path, 4. The method according to claim 1, characterized in that that said guide has a portion with a curved axis. 5. The method according to claim 1, characterized in that the strand in its passage is only supported from below by the secondary cooling zone. 6. Apparatus for performing the method according to claim 1, characterized by an open at both ends, the strand (16) forming a thin solidified edge zone (13) cooling mold (1O) ₇ through a guide for the strand between the mold and a Secondary cooling zone, which guide has a straight section at the inlet and outlet end and a curved section between these straight sections, so that a strand that has passed through is first curved and then straightened again, using coolant to maintain the thin solidified edge zone of the strand running through this guide , by organs (4O) to support the strand as it passes through the - 22 - 009812/0882 ι öb whether Secondary cooling zone and through organs for direct application of coolant (43) on the strand in the secondary cooling zone to complete the solidification of the strand. 7. Apparatus according to claim 6, characterized by rollers (42) for pulling out the strand from the mold, which hollows are placed at the entrance of the secondary cooling zone in order to reduce the length of the material to be drawn through them Strands to a minimum. 8. Apparatus according to claim 6, characterized in that that said guide consists of several elements (151-156), each of which has an upper and a lower plate (17, 18), which are water-cooled and so formed / that water through the plates can be passed to form a water film between the plate and the adjacent strand surface. 9 .. Vorrichttang isach claim 6, characterized in that the curved section of said guide has a radius of curvature which is selected so large that the elongation on the outer curve of the strand surfaces is not more than 2 V'2,% . 10. The device according to claim 6 ,. marked through a pouring nozzle protruding into the mold opening for introducing the liquid metal into the mold. ... ■■ '-' 23 '.- ■ .- ■. 009812/06 8 2 11. The device according to claim 10, characterized in that to initiate the 3-strand formation a cold strand is insertable into the mold, which has a projection (62) which extends along the lower The wall of the mold protrudes under the snout (14) to prevent metal from directly striking the lower wall of the mold to prevent as long as the cold strand is in the mold. 12. The device according to claim 6, characterized in that the cooling in said guide can be controlled in such a way that the temperature on the surface of the strand passing through the guide is between 1095 ° C and 700 ° C. CONCAST INCORPORATED - 24 - 0 09812/0582 Leer.se ι f e