EP3486001B1 - Thin-slab caster with replaceable machine head - Google Patents

Description

Technical field

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 products from steel, further to a continuous casting plant which has such a machine head group, and a method for the continuous casting of semi-finished products for the production of flat products.

Background of the Invention

In continuous casting in the metallurgical field, liquid metal, such as a molten steel, is usually fed from a ladle via a distributor channel through a dip tube made of refractory material to 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 then initially guided downward by means of a strand guide, while it gradually cools and solidifies from the outside inwards. If the casting strand is deflected by the strand guide along an arc, straightened and then transported horizontally, the system is referred to as a "vertical bending system". The strand guide, especially in the bending area, is usually made up of several construction-like segments. The segments have rollers which are arranged in pairs and are partially driven in order to transport and guide the strand in a conveying direction. It is possible to reduce the thickness of the slab or thin slab with a liquid core, for example via "liquid core reduction". For this purpose, the segments of the strand guide are preferably designed to be adjustable. During transport through the strand guide, the strand is directly cooled by means of secondary cooling cooled by either water or a water / air mixture, causing it to solidify from the outside in.

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 subjected to high thermal, abrasive and chemical stress. It is therefore a component that is subject to wear and has to be reworked or replaced regularly. For example, they are concerned with replacing the mold in continuous casting plants DE 27 29 457 A1 and WO 97/44150 A1 . Here describes the WO 97/44150 A1 a solution for long products (billet or blooms). Furthermore, the WO 97/44150 A1 the production of different dimensions.

Continuous casting plants that are designed for casting flat products with a thickness of less than 120 mm are referred to as thin slab plants. Various types of steel and the thinnest dimensions can be produced as hot strip on thin slab lines. Thin slab plants are equipped with a hopper mold as a machine head. Such a funnel mold with dip tube is in the DE 197 10 791 C2 described. The funnel is provided when pouring thin slabs, so that the immersion tube that feeds the molten metal to the mold has enough space.

Peritectically solidifying and other crack-critical steel grades have the special feature that the strand shell, which has already solidified in the mold, but undergoes a volume jump (shrinkage by approximately 0.5%) due to a phase change (from delta ferrite to austenite). This creates tensile stresses that can lead to cracks and breakthroughs more often than with other types of steel. Peritectic or other crack sensitive Steel grades are therefore difficult to cast on thin slab lines with a funnel mold in an operational and quality-safe manner. For this reason, according to the current state of the art, two casting machines are required to cover the entire range of steel grades to the extent described above.

The DE 39 09 900 A1 describes a continuous casting mold for casting steel strip. The continuous casting mold can be designed with continuously parallel broad side walls or with funnel-shaped wide side walls in the pouring area and parallel in the remaining area.

Presentation of the invention

An object of the invention is to improve the operational reliability during casting and / or to improve the surface quality of continuously cast semi-finished products, preferably slabs or thin slabs for the manufacture of flat products from steel, and / or to increase the flexibility of a continuous casting installation, in particular with regard to the variety of castable steel types and / or castable formats improve; this is preferably done in a technically simple and / or retrofittable and / or inexpensive manner.

The object is achieved with a machine head group for a continuous caster with the features of claim 1, a continuous caster with the features of claim 9 and a method with the features of claim 13. Advantageous further developments follow from the subclaims, 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 field. Poured are strand-shaped products made of a metal, in particular a metal alloy, preferably thin slabs or slabs made of steel.

The machine head group comprises at least a first machine head and a second machine head. It should be pointed out that the terms "first" and "second" do not convey any order or sequence or the like, but only serve to linguistically differentiate the relevant components or features.

The first machine head is equipped with a funnel mold. In the field, a funnel mold is a mold with tapered walls, ie with a conical or frustoconical shape, preferably made of copper or a copper alloy, which can be coated. The funnel mold is set up in order to discharge the strand, preferably downwards (seen in the direction of gravity). For this purpose, the melt to be cast is fed to the mold and brought into the desired strand or slab shape by the mold by the strand which has not yet solidified emerging from a correspondingly shaped outlet opening of the mold. The funnel is provided when pouring thin slabs, so that the immersion tube that feeds the molten metal to the mold has enough space. A mold section with a rectangular casting cross section can be located below the funnel, preferably in the region of the outlet opening of the mold. The first machine head preferably also has a first machine head segment with a plurality of rollers arranged in pairs, which can be partially driven, for transporting the strand-shaped product. According to this preferred embodiment, the first machine head segment adjoins the funnel mold as seen in the conveying direction of the strand-shaped product. The rollers of the first machine head segment arranged in pairs each form a gap and, overall, a gap passage through which the strand-shaped product passes in the conveying direction. The funnel mold and the first machine head segment are preferably adapted to one another and / or combined with one another in such a way that the first machine head forms a module which can be installed and exchanged as a structural unit in the continuous casting installation.

The second machine head has a mold, which is provided with a section of constant casting cross section along the conveying direction. For this purpose, the mold preferably has plane-parallel walls, for example made of copper, or a copper alloy that can be coated. Like the funnel mold of the first machine head, the mold of the second machine head is set up to discharge the strand, preferably downwards (seen in the direction of gravity). For this purpose, the melt to be cast is fed to the mold and brought into the desired strand or slab shape by the mold, in that the strand which has not yet solidified 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 also has a second machine head segment with a plurality of rollers arranged in pairs, which can be partially driven, for transporting the strand-shaped product. According to this preferred embodiment, the second machine head segment adjoins the mold as seen in the conveying direction of the strand-shaped product. The rollers of the second machine head segment arranged in pairs likewise each form a gap and, overall, a gap passage through which the strand-like product passes in the conveying direction. The mold of the second machine head and the second machine head segment are preferably matched to one another and / or combined with one another in such a way that the second machine head forms a module which can be installed and exchanged as a structural unit in the continuous casting installation.

Both machine heads are designed to be interchangeable so that the entire quality and thickness range can be cast reliably and in a reliable manner.

The machine head group obtained in this way enables an improvement of the surface quality and operational safety when casting difficult types of steel. In particular, the machine head group enables the casting of both peritectically solidifying and non-peritectically solidifying steel grades. For the casting of peritectically solidifying steel grades, casting can be carried out with the second machine head. In this case, the use of mold plates without a funnel results in a low-stress formation of the strand shell, so that the formation of an error-free one Favor surface. This special design of the machine head enables the use of a thin slab system even for thick slabs without having to adapt the layout of the entire machine. A continuous caster equipped with the machine head group shown allows a large variety of steel grades and a large range of thicknesses, which saves installation space and costs by dispensing with the acquisition and operation of two continuous caster systems that would otherwise be necessary to meet the required requirements To represent steel grades and thickness range.

The casting of the strand-like product by means of the second machine head is preferably carried out at a lower casting speed due to the thickness of the casting than the casting of the strand-like product by means of the first machine head. The surface quality and operational reliability when casting peritectic or crack-critical steel grades can be further improved in this way.

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

The rollers of the first machine head segment and / or of the second machine head segment are preferably arranged such that they can be adjusted such that the strand-shaped product in the corresponding machine head segment is reduced in thickness during transport. In other words, the rolls in question are arranged or adjustable in such a way that the thickness of the strand emerging from the mold in the associated machine head segment is reduced during the regular casting process. Work this way the mold and the associated machine head segment together in order to be able to realize a larger 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 any rolling mill for reducing the thickness after solidification can consequently be designed to be smaller.

The structure of the first machine head segment and the structure of the second machine head segment preferably differ. For example, the rollers of the first machine head segment arranged in pairs form a first gap and the rollers of the second machine head segment arranged in pairs form a second gap, with the width (ie the intended dimension of the narrow side of the strand-shaped product) preferably decreasing in the conveying direction of at least the second gap ; the widths of both the first and the second gap passage decrease particularly preferably, the degree of decrease of the second gap passage being smaller than that of the first gap passage. Peritectically solidifying or generally crack-critical steel grades are preferably cast using the second machine head. In order to keep the strand shell low in tension even after leaving the mold, the degree of decrease in the second gap is preferably low, which favors the formation of a flawless surface.

Before casting, the roll diameters and / or roll spacings of rolls of the segments and / or machine head segments are preferably optimized for the thickness range and / or casting speed range that can be cast by means of the first machine head and the second machine head. This ensures optimal support of the strand both for the entire thickness range and for the large casting speed range and thus the temperature range of the slab, as a result of which strand shell faults can be suppressed. It is Pay particular attention to the requirements resulting 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, which is directed either to one end of the range shown (high casting speeds and small thicknesses resulting in rapid solidification) or the other end of the range shown (large thicknesses and low casting speeds). According to the preferred embodiment, the role plan is designed in such a way that the entire area is taken into account.

The first machine head is preferably set up to cast strand-like products with a casting thickness of up to 120 mm, particularly preferably in the range from 50 mm to 120 mm; and the second machine head is preferably set up to cast strand-shaped products with a casting thickness of up to 200 mm, particularly preferably in the range from 120 mm to 170 mm. According to this embodiment, the use of a mold type with larger dimensions is provided for the production of crack-critical steel types, because this has no funnel, which can have an unfavorable effect when casting crack-critical steel types. In addition - this results in a synergetic way from the optimization for crack-critical steel grades - an expansion of the realizable casting formats is created, even on plants that are designed as thin slab plants.

The first machine head and the second machine head preferably have identical or similar components - such as housings, housing parts, fasteners, etc. - so that they interact in a modular manner with the continuous casting installation. This means that 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 caster according to the invention is used to cast strand-like products, preferably steel slabs, and has a machine head group as described above.

The continuous casting plant is preferably a thin slab plant, i. H. a continuous caster that was originally designed for casting thicknesses up to 120 mm. The use of the machine head group set out above thus enables a technically elegant retrofit of a thin slab plant in such a way that formats up to 200 mm casting thickness and / or difficult types of steel can be realized with the plant due to the design of the funnel, which is not necessary due to the design.

Further advantages and features of the present invention are evident from the following description of preferred exemplary embodiments. The features described there can be implemented on their own or in combination with one or more of the features set out above, provided that the features do not contradict each other. The following description of the preferred embodiments is made with reference to the accompanying drawings.

Brief description of the figures

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

Detailed description of preferred embodiments

Preferred exemplary embodiments are described below with reference to the figures. The same, similar or equivalent elements are provided with identical reference numerals, and a repeated description of these elements is partially omitted in order to avoid redundancies.

The Figure 1 shows schematically a continuous casting plant 1, which is primarily designed and set up as a thin slab plant. The continuous caster 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 similar and together form a modular strand guide. The strand, issued vertically downwards from an installed machine head 2a or 2b (cf. Figures 2 and 3rd ), reaches a bending area, formed by the segments 3, where it is subjected to bending forces on the one hand and is transported in the conveying direction F on the other. This is done by means of rollers 31 arranged in pairs and partially driven. One or more segments 3 should be adjustable to map the large thickness range, thereby defining the thickness of the gap passage formed by the rollers 31. 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 Figures 1 to 3 is shown. The adjustability can be realized hydraulically, electrically or in another way will. For this purpose, the relevant segment 3 can have one or more electrical connections and / or media connections 32, such as hydraulic connections. During transport, the strand is actively cooled by a secondary cooling, not shown, whereby it gradually solidifies from the outside in. The continuous caster is designed as a "vertical turning system". However, it should be pointed out that the strand guidance can also be carried out in another way, for example in the form of a vertical casting machine or a circular arc casting machine.

According to the present exemplary embodiment, each machine head 2a, 2b has a mold 21a, 21b and a machine head segment 22a, 22b. The mold 21a is designed as a funnel mold which, together with the machine head segment 22a, forms a module-like component or structural unit as a first segment for strand guidance. 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 designed as a mold with plane-parallel broad side plates, forms a module-like component or structural unit with the machine head segment 22b as a first segment for strand guidance. The mold 21b is preferably a mold made of copper plates (or plates of a copper alloy that can be coated), with plane-parallel plates on the broad sides and likewise plane-parallel plates on the narrow sides, which are adapted to a comparatively high casting thickness of, 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. This enables the machine heads 22a and 22b to be replaced quickly and easily.

In order to adapt the machine head segments 22a and 22b to the strand guide of the installation, they can be designed so that the gap passage formed by the rollers 23a and 23b can be adjusted. In particular, the thickness of the gap can decrease in the conveying direction, on the one hand to compensate for the thermal shrinkage and on the other hand to achieve an improvement in the internal quality, as is the case, for example, and in different forms for the two machine head segments 22a and 22b of FIG Figures 1 to 3 is shown. The adjustability can be realized hydraulically, electrically or in another way. For this purpose, the relevant machine head segment 22a, 22b can have one or more media connections 24a, 24b, for example hydraulic connections.

According to an exemplary embodiment, the mold opening dimension of the funnel mold 21a is approximately 100 to 120 mm, with which a slab thickness of approximately 120 to 80 mm can be realized. The mold 21b preferably has a mold opening dimension of approximately 150 mm.

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

The thin slab system 1 described with the two machine heads 2a and 2b enables an improvement in the surface quality and operational reliability when casting crack-critical steel types 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 with thin slab casting with the machine head 2a. In the case of arc casting machines, a quick-change device can be provided for the last horizontal segments, so that these can be changed quickly against "dummy" segments at the same time, in order to accommodate changed solidification lengths.

By replacing the machine head 2a with the machine head 2b, the casting thickness is increased to up to 150 mm in order to minimize the tensions during the formation of the strand shell without funnel-shaped mold 21b and to support the low casting speeds. This compensation mechanism enables the thin slab system to be used even for thick slabs without having to adjust the layout of the entire machine. The continuous caster 1 allows a large variety of steel types and a large casting thickness range, whereby construction space and costs can be saved by dispensing with the acquisition and operation of two continuous caster systems that would otherwise be necessary to represent the required steel types and thickness range.

In contrast to the first embodiment of the Figures 1 to 3 , The machine heads 2a and 2b of the second embodiment of the Figures 4 to 6 no segments belonging to the machine head, but the first segment 3 according to the second embodiment is used for both machine heads with appropriate employment. Otherwise, the structure and the mode of operation of the two exemplary embodiments are essentially the same.

The process of changing the machine heads 2a and 2b is shown in FIGS Figures 5 and 6 shown. Since the machine heads 2a and 2b are formed by the respective molds 21a and 21b without these having to be individually adapted machine head segments, it is particularly preferred in the context of the second embodiment that at least the first segment 3 of the strand guide (viewed in the conveying direction F) can be adjusted, as a result of which the gap passage formed by the rollers 23a and 23b quickly and reliably to the current mold 21a , 21b can be adjusted. In the present example, two segments 3 are even provided so that they can be adjusted. The adjustability can be realized hydraulically, electrically or in another way. 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.

As far as applicable, all individual features that are shown in the exemplary embodiments can be combined and / or exchanged with one another without leaving the scope of the invention.

Reference list

1

Continuous caster

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

Rolling the first machine head segment

23b

Rolling the second machine head segment

24a

Media connection

24b

Media connection

3rd

segment

31

Roles of the segment

32

Media connection

F

Direction of conveyance

Claims (15)

1. Machine head group for a continuous casting plant (1) for continuous casting of semi-finished products, preferably slabs or thin slabs for production of flat products from steel, wherein the machine head group comprises at least one first machine head (2) and second machine head (2b), the first machine head (2a) comprises a funnel mould (21a) and the second machine head (2b) comprises a mould (21b) with a portion of constant casting cross-section in conveying direction (F) of the strip-shaped product, wherein the first machine head (2a) and the second machine head (2b) are constructed to be interchangeable in the continuous casting plant (1).
2. Machine head group according to claim 1, characterised in that the mould (21b) has two opposite wide sides and two opposite narrow sides, which are each formed by planoparallel plates, preferably of copper or a copper alloy, which can be coated.
3. Machine head group according to claim 1 or 2, characterised in that the first machine head (2a) has a first machine head segment (22a), which is connected with the funnel mould (21a) in the conveying direction (F) of the strip-shaped product, with a plurality of rollers (23a), which are arranged in pairs, for transport of the strip-shaped product, and/or the section machine head (2b) comprises a second machine head segment (22b), which is connected with the mould (21b) in the conveying direction (F) of the strip-shaped product, with a plurality of rollers (23b), which are arranged in pairs, for transport of the strip-shaped product.
4. Machine head group according to claim 3, characterised in that the rollers (23a, 23b) of the first machine head segment (22a) and/or of the second machine head segment (22b) are so arranged, preferably adjustably, that a reduction in thickness of the strip-shaped product can take place in the corresponding machine head segment.
5. Machine head group according to claim 3 or 4, characterised in that the construction of the first machine head segment (22a) and the construction of the second machine head segment (22b) differ.
6. Machine head group according to claim 5, characterised in that the rollers (23a), which are arranged in pairs, of the first machine head segment (22a) form a first gap path and the rollers (23b), which are arranged in pairs, of the second machine head segment (22b) form a second gap path, wherein the gap thickness at least of the second gap path decreases in conveying direction (F), preferably the gap thicknesses of both the first and the second gap path decrease, wherein the degree of decrease of the second gap path is less than that of the first gap path.
7. Machine head group according to any one of the preceding claims, characterised in that the first machine head (2a) is arranged to cast strip-shaped products with a casting thickness up to 120 millimetres, preferably in the range of 50 millimetres to 120 millimetres, and the second machine head (2b) is arranged to cast strip-shaped products with a casting thickness up to 200 millimetres, preferably in the range of 120 millimetres to 170 millimetres.
8. Machine head group according to any one of the preceding claims, characterised in that the first machine head (2a) and the second machine head (2b) comprise identical or constructionally similar components, for example housings, housing parts and/or fastening means, so that these can co-operate in modular manner with a continuous casting plant (1).
9. Continuous casting plant (1) for continuous casting of semi-finished products, preferably slabs or thin slabs for production of flat products of steel, which comprises a machine head group according to any one of the preceding claims.
10. Continuous casting plant (1) according to claim 9, characterised in that this is a thin slab plant.
11. Continuous casting plant (1) according to claim 9 or 10, characterised in that this comprises one or more segments (3) with a plurality of rollers (31), which are arranged in pairs and which are preferably in part driven, for the transport of the strip-shaped product, wherein rollers (31) at least of the first segment (3) are adjustable as seen in conveying direction (F).
12. Continuous casting plant (1) according to claim 11, characterised in that the roller diameter and/or roller spacings is or are optimised for the overall range of thickness and/or the range of rate of casting.
13. Method for continuous casting of semi-finished products, preferably slabs or thin slabs for production of flat products from steel, which is carried out by means of a continuous casting plant (1) according to any one of claims 9 to 12.
14. Method according to claim 12, characterised in that the casting of the strip-shaped product is carried out by means of the second machine head (2b) at a lower rate of casting than the casting of the strip-shaped product by means of the first machine head (2a).
15. Method according to claim 13 or 14, characterised in that prior to the casting an optimisation of the roller diameter and/or roller spacings of rollers of segments (3) and/or machine head segments (22a, 22b) for the thickness range and/or range of rate of casting castable by means of the first machine head (2a) and the second machine head (2b) is carried out.

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