EP3486001A1 - Thin-slab caster with replaceable machine head - Google Patents

Abstract

Machine head group for a continuous casting plant (1) for the continuous casting of semi-finished products, preferably slabs or thin slabs for the production of flat steel products, continuous casting plant comprising such a machine head group, as well as processes for the continuous casting of semi-finished products. The machine head group comprises at least a first machine head (2a) and a second machine head (2b), wherein the first machine head (2a) has a hopper mold (21a) and the second machine head (2b) has a mold (21b) with a portion of constant casting cross section in the conveying direction (F) of the rope-shaped product.

Description

Technical area

The invention relates to a machine head group for a continuous casting plant for the continuous casting of semi-finished products, preferably slabs or thin slabs for the production of flat steel products, also a continuous casting plant having such a machine head group, and a method for continuous casting of semi-finished products for the production of flat products.

Background of the invention

In continuous casting in the metallurgical region, liquid metal, such as a molten steel, from a ladle is usually fed through a distributor trough through a dip tube made of refractory material of a mold. The mold defines the rectangular cross section of the later slab or thin slab from the molten steel. The strand, which has not yet solidified, emerges from the mold and is subsequently guided downwards by means of a strand guide, while it successively cools from outside to inside and solidifies. If the casting strand is deflected by the strand guide along an arc, directed and then further transported horizontally, the plant is called a "vertical turning plant". The strand guide, in particular in the bending area, is usually constructed of several construction-like segments. The segments have paired and partially driven rollers for transporting and guiding the strand in a conveying direction. It is possible to reduce the slab or thin slab with liquid core in thickness, for example via "liquid core reduction". For this purpose, the segments of the strand guide are preferably made adjustable. During transport through the strand guide, the strand becomes by means of a direct secondary cooling cooled by either water or a water / air mixture, whereby it solidifies from the outside inwards.

Continuous casting plants of the type described above are for example in the DE 10 2015 210 865 A1 and DE 10 2015 215 187 A1 described.

Due to the high temperature and properties of the liquid steel in combination with the partially liquid casting powder, the mold is thermally, abrasive and chemically stressed. It is therefore a component that is subject to wear and must be regularly reworked or replaced. With the replacement of the mold in continuous casting, for example, the DE 27 29 457 A1 and WO 97/44150 A1 , This describes the WO 97/44150 A1 a solution for long products (billet or pre-block casters). Furthermore, the names WO 97/44150 A1 the production of different dimensions.

Continuous casting plants designed to cast flat products with thicknesses of less than 120 mm are referred to as thin slab plants. On thin slab plants, different types of steel and the thinnest dimensions can be produced as a hot strip. Thin slab plants are provided with a funnel mold as a machine head. Such a hopper mold with dip tube is in the DE 197 10 791 C2 described. The funnel is provided when casting thin slabs, so that the dip tube, which supplies the liquid molten metal to the mold, finds enough space.

Peritectically solidifying and other crack-critical steel grades have the peculiarity that the strand shell, which has already solidified in the mold, experiences a volume jump (shrinkage of about 0.5%) due to a phase transformation (from delta ferrite to austenite). This creates tensile stresses that can lead to cracks and breakthroughs more frequently than with other steel grades. Peritectic or other crack-sensitive Steel grades are therefore difficult to cast on thin slab plants with hopper molds in a manner that is safe in terms of operation and quality. For this reason, two casting machines are required in the current state of the art to cover the entire steel grade range to the extent described above.

Presentation of the invention

It is an object of the invention to improve the operational safety during casting and / or the surface quality of continuously cast semifinished products, preferably slabs or thin slabs for the production of flat steel products, and / or the flexibility of a continuous casting plant, in particular with regard to the castable variety of cast steel and / or castable formats improve; this preferably in a technically simple and / or retrofittable and / or cost-effective manner.

The object is achieved with a machine head group for a continuous casting with the features of claim 1, a continuous casting with the features of claim 9 and a method having the features of claim 13. Advantageous further developments follow from the dependent claims, the following description of the invention and the description preferred embodiments.

The machine head group according to the invention is set up for a continuous casting plant for the continuous casting of semi-finished products in the metallurgical area. In this case, strand-shaped products are cast from a metal, in particular a metal alloy, preferably thin slabs or slabs made of steel.

The machine head group includes at least a first machine head and a second machine head. It should be noted that the terms "first" and "second" mean no order or order or provide the same, but only serve the linguistic distinction of the relevant components or features.

The first machine head is equipped with a hopper mold. As a funnel mold is in the field a mold with tapered walls, d. H. designated with a conical or frusto-conical shape, preferably of copper or a copper alloy, which may be coated. The hopper mold is arranged to deploy the skein, preferably downwardly (viewed in the direction of gravity). For this purpose, the mold is fed to the melt to be cast and brought from the mold in the desired strand or slab form by the not yet solidified strand exits from a correspondingly shaped outlet opening of the mold. The funnel is provided when casting thin slabs, so that the dip tube, which supplies the liquid molten metal to the mold, finds enough space. A mold section with a rectangular casting cross-section can be located below the funnel, preferably in the region of the exit opening of the mold. The first machine head preferably further includes a first machine head segment having a plurality of paired rollers, which may be partially driven, for transporting the rope-shaped product. According to this preferred embodiment, the first machine head segment, viewed in the conveying direction of the strand-like product, adjoins the funnel mold. The paired rollers of the first machine head segment each form a gap and a total of a gap, through which the strand-shaped product occurs in the conveying direction. The hopper mold and the first machine head segment are preferably matched and / or combined in a manner such that the first machine head forms a module that is installable and replaceable as a unit in the continuous casting machine.

The second machine head has a mold, which is provided with a portion of constant casting cross-section along the conveying direction. For this purpose, the mold preferably has plane-parallel walls, for example Copper, or a copper alloy, which may be coated on. Like the funnel mold of the first machine head, the mold of the second machine head is arranged to deploy the strand, preferably downwardly (viewed in the direction of gravity). For this purpose, the mold is fed to the melt to be cast and brought from the mold in the desired strand or slab mold by the not yet solidified strand is discharged from the correspondingly shaped outlet opening of the mold. This mold preferably has a rectangular cross-section in the casting direction over the entire length. The second machine head preferably further comprises a second machine head segment having a plurality of paired rollers, which may be partially driven, for transporting the rope-shaped product. According to this preferred embodiment, the second machine head segment, viewed in the conveying direction of the strand-like product, adjoins the mold. The paired rollers of the second machine head segment also each form a gap and a total of a gap, through which the strand-shaped product occurs in the conveying direction. The mold of the second machine head and the second machine head segment are preferably adapted to one another and / or combined in such a way that the second machine head forms a module that can be installed and exchanged as a structural unit in the continuous casting plant.

Both machine head groups are interchangeable with each other in order to be able to pour the entire range of quality and thickness reliably and safely.

The machine head group thus obtained enables an improvement in the surface quality and operational safety when casting difficult steels. Specifically, the machine head group allows the casting of both peritectically solidifying and non-peritectically solidifying grades of steel. For pouring peritectically solidifying steel grades, casting can be done with the second machine head. This is done by using mold plates without Funnel a lower tension training of the strand shell achieved so as to favor the formation of a flawless surface. This special design of the machine head allows the use of a thin slab plant even for thicker slabs, without having to adjust the layout of the entire machine. A continuous caster equipped with the machine head group set out permits a wide variety of steel grades and a large thickness range, which can save installation space and costs by eliminating the need to purchase and operate two continuous casters that would otherwise be required to meet the requirements Represent steel grade and thickness range.

The casting of the rope-shaped product by means of the second machine head is preferably due to casting thickness, with a lower casting speed than the casting of the rope-shaped product by means of the second machine head. The surface quality and operational safety when casting peritectic or crack-critical steel grades can thus be further improved.

Preferably, the mold of the second machine head has two opposite broad sides and two opposite narrow sides, which are each formed by plane-parallel plates, preferably made of copper or a copper alloy, which may be coated. With such a mold construction of the second machine head, the casting quality of thick stranded products and / or difficult steel grades can be further improved.

Preferably, the rollers of the first machine head segment and / or the second machine head segment are arranged to be approximately adjustable such that during transport, a reduction in the thickness of the rope-shaped product takes place in the corresponding machine head segment. In other words, the respective rolls are arranged or adjustable so that during the regular casting process the thickness of the strand emerging from the mold in the associated machine head segment is reduced. Work that way the mold and the associated machine head segment together in order to realize a greater thickness range with a continuous caster originally designed for thin slabs. Furthermore, the system can be made more compact overall, since part of the reduction in thickness already takes place in the machine head segment and a possible rolling mill for reducing the thickness after solidification can thus be designed smaller.

Preferably, the structure of the first machine head segment and the structure of the second machine head segment differ. Thus, the paired rollers of the first machine head segment approximately form a first gap and form the paired rollers of the second machine head segment a second gap, preferably the width (ie, the intended dimension of the narrow side of the rope-shaped product) decreases at least the second gap in the conveying direction ; Particularly preferably, the widths of both the first and the second splitting ducts decrease, the degree of decrease of the second splitting duct being smaller than that of the first splitting duct. The casting of peritectically solidifying or generally crack-critical steel grades preferably takes place with the second machine head. In order to keep the strand shell low in tension in this case even after leaving the mold, the degree of decrease of the second gap is preferably low, whereby the formation of a defect-free surface is favored.

Preferably, prior to casting, an optimization of the roll diameters and / or roll spacings of rolls of the segments and / or machine head segments for the thickness range and / or casting speed range pourable by means of the first machine head and the second machine head takes place. Thus, an optimal support of the strand is ensured both for the entire thickness range as well as for the large casting speed range and thus temperature range of the slab, whereby strand shell defects can be suppressed. It is pay special attention to the requirements that arise from the wide range of steel grades with different solidification and ductility characteristics, taking into account the strand dimensions. The optimization thus differs from a conventional design directed either to one end of the illustrated range (high casting speeds and small thicknesses resulting in rapid through-solidification) or the other end of the illustrated range (large thicknesses and low casting speeds). According to the preferred embodiment, a design of the rolling schedule is realized such that the whole area is taken into consideration.

Preferably, the first machine head is adapted to pour strand-shaped products having a casting thickness of up to 120 mm, more preferably in the range of 50 mm to 120 mm; and the second machine head is preferably arranged to cast strand-shaped products having a casting thickness of up to 200 mm, more preferably in the range of 120 mm to 170 mm. According to this embodiment, the use of a mold type with a larger dimension is provided for the production of crack-critical steel grades because it does not have a hopper which can have an unfavorable effect when casting crack-critical steel grades. In addition - this results in a synergetic way from the optimization for crack-critical steel grades - an extension of the feasible casting formats is created, even on plants, which are designed as thin slab plants.

The first machine head and the second machine head preferably have identical or construction-like components - such as housing, housing parts, fasteners, etc. - on, so that they interact in a modular manner with the continuous casting. As a result, the machine head change can be carried out quickly in order to be able to integrate a machine head change into production planning without delay.

The continuous casting plant according to the invention is used for casting strand-like products, preferably steel slabs, and has a machine head group according to the above description.

The continuous casting plant is preferably a thin slab plant, i. H. a continuous casting plant that was originally designed for casting thicknesses up to 120 mm. The use of the above-described machine head group thus allows a technically elegant retrofitting of a thin slab plant such that formats of up to 200 mm casting thickness and / or difficult steel grades can be realized due to the design-unnecessary funnel with the system.

Further advantages and features of the present invention will be apparent from the following description of preferred embodiments. The features described therein may be implemented alone or in combination with one or more of the features set forth above insofar as the features do not conflict. The following description of the preferred embodiments will be made with reference to the accompanying drawings.

Brief description of the figures

• The FIG. 1 schematically shows a continuous casting plant with a first and a second machine head according to a first embodiment.
• The FIG. 2 schematically shows the continuous casting of the FIG. 1 with the first machine head installed.
• The FIG. 3 schematically shows the continuous casting of the FIG. 1 with the second machine head installed.
• The FIG. 4 schematically shows a continuous casting plant with a first and a second machine head according to a second embodiment.
• The FIG. 5 schematically shows the continuous casting of the FIG. 4 with the first machine head installed.
• The FIG. 6 schematically shows the continuous casting of the FIG. 4 with the second machine head installed.

Detailed description of preferred embodiments

In the following, preferred embodiments will be described with reference to the figures. In this case, identical, similar or equivalent elements are provided with identical reference numerals, and a repetitive description of these elements is partially omitted in order to avoid redundancies.

The FIG. 1 schematically shows a continuous casting plant 1, which is designed and set up primarily as a thin slab plant. The continuous casting plant 1 has at least two machine heads 2a, 2b (described in detail below) and a plurality of segments 3.

The segments 3 are identical or construction-like and together form a modular design strand guide. The strand, issued vertically down from an installed machine head 2a or 2b (see. Figures 2 and 3 ), passes into a bending region, formed by the segments 3, where it is subjected to bending forces on the one hand and to the other in the conveying direction F is transported. This is done by means of paired and partially driven rollers 31. One or more segments 3 should be adjustable to image the large thickness range, whereby the thickness of the gap formed by the rollers 31 is defined. In particular, the thickness of the gap can decrease in the conveying direction, as exemplified for the upper segment 3 (ie, the first segment seen in the conveying direction F) in the FIGS. 1 to 3 is shown. The adjustability can be realized hydraulically, electrically or in other ways become. For this purpose, the relevant segment 3 may have one or more electrical connections and / or media connections 32, for instance hydraulic connections. During transport, the strand is actively cooled by a secondary cooling, not shown, whereby it gradually solidifies from outside to inside. The continuous casting plant is designed as a "vertical turning plant". It should be noted, however, that the strand guide can be accomplished in other ways, such as in the form of a vertical caster or a circular arc casting machine.

Each machine head 2a, 2b comprises, according to the present exemplary embodiment, a mold 21a, 21b and a machine head segment 22a, 22b. The mold 21a is embodied as a funnel mold that forms a modular component or assembly with the machine head segment 22a as a first strand guide segment. The funnel mold 21a and the machine head segment 22a are matched to one another so that the critical transition between the mold and the upper region of the strand guide does not have to be readjusted after a machine head change. In an analogous manner, the mold 21b, preferably embodied as a mold with plane-parallel broad side plates, forms, with the machine head segment 22b as a first segment for strand guidance, a modular component or structural unit. The mold 21b is preferably a mold of copper plates (or plates of a copper alloy, which may be coated), with plane-parallel plates on the broad sides and also plane-parallel plates on the narrow sides, which are adapted to a relatively high casting thickness, for example, 150 mm. The mold 21b and the machine head segment 22b are matched to one another, so that the critical transition between the mold and the upper region of the strand guide does not have to be readjusted after a machine head change. As a result, the replacement of the machine heads 22a and 22b can be done easily and quickly.

In order to adapt the machine head segments 22a and 22b to the strand guide of the installation, these can be made adjustable so that the gap formed by the rollers 23a and 23b can be adjusted. In particular, the thickness of the gap can decrease in the conveying direction to compensate for the thermal shrinkage on the one hand and on the other hand to achieve an improvement in the internal quality, as exemplified and in different form for the two machine head segments 22a and 22b of FIGS. 1 to 3 is shown. The adjustability can be realized hydraulically, electrically or in other ways. For this purpose, the relevant machine head segment 22a, 22b may have one or more media connections 24a, 24b, for instance hydraulic connections.

According to an exemplary embodiment, the Kokillenöffnungsmaß the hopper mold 21a is about 100 to 120 mm, whereby a slab thickness of about 120 to 80 mm is feasible. The mold 21b preferably has a Kokillenöffnungsmaß of about 150 mm.

The continuous casting machine 1 with installed machine head 2a, which has the hopper mold 21a, is suitable for casting thin slabs of non-peritectically solidifying steel grades in a casting thickness range of 50 to 120 mm. The machine head 2a can now according to the in the FIGS. 1 to 3 embodiment shown are replaced by the machine head 2b with plane-parallel plates on the broad sides and adapted to the new casting thickness narrow sides. At the same time, the associated machine head segments 22a and 22b are exchanged. By the molds 21 a, 21 b and the associated machine head segments 22 a, 22 b each form a module, the change process, shown in the Figures 2 and 3 , be shortened to about the time of a regular machine head change without attached segments.

The stated thin slab plant 1 with the two machine heads 2a and 2b enables an improvement of the surface quality and operational safety when casting crack-critical steel grades and / or casting thicknesses in the range of 150 mm. For this purpose, the casting with the machine head 2b is preferably carried out at lower casting speeds than in thin slab casting with the machine head 2a. In Bogengießmaschinen a quick-change device for the last horizontal segments can be provided so that they can be changed quickly against "dummy" segments at the same time to meet changed solidification lengths.

By replacing the machine head 2a with the machine head 2b, the casting thickness is increased up to 150 mm to minimize stress in strand shell formation without the funnel-shaped mold 21b and to support the low casting speeds. This compensation mechanism allows the use of the thin slab plant even for thicker slabs, without having to adjust the layout of the entire machine. The continuous caster 1 allows a large variety of steel grades and a large Gießdickenbereich, which space and cost can be saved by the purchase and operation of two continuous casters can be omitted, which would otherwise be necessary to represent the required steel grades and thickness range.

In contrast to the first embodiment described above FIGS. 1 to 3 , The machine heads 2a and 2b of the second embodiment of the FIGS. 4 to 6 no machine head own segments, but the first segment 3 according to the second embodiment is used for both machine heads under appropriate employment. Incidentally, the structure and operation of the two exemplary embodiments is substantially the same.

The changing operation of the machine heads 2a and 2b is in the Figures 5 and 6 shown. Since the machine heads 2a and 2b are formed by the respective molds 21a and 21b without being customized with them In the context of the second embodiment, it is particularly preferred that at least the first segment 3 of the strand guide (seen in the conveying direction F) can be adjusted, as a result of which the gap formed by the rollers 23a and 23b can be quickly and reliably applied to the current mold 21a , 21b can be adjusted. In the present example, even two segments 3 are provided adjustable. The adjustability can be realized hydraulically, electrically or in other ways. For this purpose, the relevant segment 3 can have one or more actuators with corresponding electrical connections and / or media connections 32, for example hydraulic connections.

Where applicable, all individual features illustrated in the embodiments may be combined and / or interchanged without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

1

continuous casting plant

2a

First machine head

2 B

Second machine head

21a

funnel mold

21b

mold

22a

First machine head segment

22b

Second machine head segment

23a

Rolls of the first machine head segment

23b

Rolls of the second machine head segment

24a

media connection

24b

media connection

3

segment

31

Rolls of the segment

32

media connection

F

conveying direction

Claims (15)

Machine head group for a continuous casting plant (1) for continuous casting of semi-finished products, preferably slabs or thin slabs for the production of flat steel products, wherein the machine head group comprises at least a first machine head (2a) and a second machine head (2b),
the first machine head (2a) has a hopper mold (21a), and
the second machine head (2b) has a mold (21b) with a section of constant casting cross-section in the conveying direction (F) of the strand-shaped product. Machine head assembly according to claim 1, characterized in that the mold (21b) has two opposite broad sides and two opposite narrow sides, each formed by plane-parallel plates, preferably made of copper or a copper alloy, which may be coated. Machine head assembly according to claim 1 or 2, characterized in that
the first machine head (2a) has a first machine head segment (22a) adjoining the funnel mold (21a) in the conveying direction (F) of the rope-shaped product and having a plurality of rollers (23a) arranged in pairs for transporting the rope-shaped product, and / or
the second machine head (2b) has a second machine head segment (22b) adjoining the mold (21b) in the conveying direction (F) of the rope-shaped product and having a plurality of rollers (23b) arranged in pairs for transporting the rope-shaped product. A machine head assembly according to claim 3, characterized in that the rollers (23a, 23b) of the first machine head segment (22a) and / or the second machine head segment (22b) are arranged, preferably adjustable, such that a reduction in the thickness of the rope-shaped product can take place in the corresponding machine head segment , Machine head assembly according to claim 3 or 4, characterized in that the structure of the first machine head segment (22a) and the structure of the second machine head segment (22b) differ. A machine head assembly according to claim 5, characterized in that the paired rollers (23a) of the first machine head segment (22a) form a first gap and the paired rollers (23b) of the second machine head segment (22b) form a second gap, the gap thickness of at least the second gap in the conveying direction (F) decreases, preferably, the thicknesses of both the first and the second splitting decreases, wherein the degree of decrease of the second splitting duct is smaller than that of the first splitting duct. Machine head assembly according to one of the preceding claims, characterized in that the first machine head (2a) is arranged to cast strand-shaped products with a casting thickness of up to 120 mm, preferably in the range of 50 mm to 120 mm, and the second machine head (2b ) is adapted to pour strand-shaped products having a casting thickness of up to 200 mm, preferably in the range of 120 mm to 170 mm. Machine head group according to one of the preceding claims, characterized in that the first machine head (2a) and the second Machine head (2b) of identical or construction-like components, for example, housing, housing parts and / or fastening means, have, so that they can interact in a modular manner with a continuous casting plant (1). Continuous casting plant (1) for the continuous casting of semi-finished products, preferably slabs or thin slabs for the production of flat products made of steel, which has a machine head group according to one of the preceding claims. Continuous casting plant (1) according to claim 9, characterized in that it is a thin slab plant. Continuous casting plant (1) according to claim 9 or 10, characterized in that it comprises one or more segments (3) with a plurality of pairs of rollers (31), which are preferably partially driven, for transporting the rope-shaped product, wherein rollers (31) at least of the first segment (3), seen in the conveying direction (F), are adjustable. Continuous casting plant (1) according to claim 11, characterized in that the roll diameter and / or roll spacing are optimized for the entire thickness range and / or casting speed range. Process for the continuous casting of semi-finished products, preferably slabs or thin slabs for the production of flat products from steel, which is carried out by means of a continuous casting plant (1) according to one of claims 9 to 12. A method according to claim 12, characterized in that the casting of the strand-like product by means of the second machine head (2b) with a casting speed lower than the casting of the rope-shaped product by means of the second machine head (2b). A method according to claim 13 or 14, characterized in that before casting an optimization of the roll diameter and / or roll distances of roles of the segments (3) and / or machine head segments (22a, 22b) for the means of the first machine head (2a) and the second Machine head (2b) pourable thickness range and / or casting speed range is made.

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