Method for casting steel and distributors for this purpose

Abstract

The invention relates to a method for continuous casting of metal, in particular steel, wherein liquid metal from a ladle, which is movably mounted, is guided by a shadow pipe into a continuous casting manifold and from the continuous casting manifold is guided via an outlet into a casting mold, wherein the continuous casting manifold compensates for the interruptions when the ladles are changed, and wherein the ladles are mounted in a moving device, characterized in that different melts with respect to their alloy composition and origin are cast successively into the manifold, wherein the successively cast, different melts are LD melts on the one hand and EAF melts on the other.

Description

[0001] The invention relates to a method for casting steel.

[0002] Continuous steel casting is a well-known process for the continuous casting of steel slabs.

[0003] For this purpose, steel is usually produced in a converter, transferred from the steel converter to a ladle and from the ladle via a distributor to the casting mold.

[0004] The distributor's function is to ensure a continuous flow of steel after one pan has emptied and the next pan has been fed in.

[0005] Basically, it must be ensured that there are no inclusions in the liquid steel, in particular neither slag particles nor components of the respective refractory lining or injection molding of the vessels nor reaction products from metallurgical treatment steps.

[0006] This is achieved in particular by the arrangement of appropriate components in a distribution trough, which generates a specific upward flow after the steel has been poured in, such that the steel is washed to the surface, allowing particles that are lighter than the steel to enter the slag or be bound by the slag.

[0007] A continuous casting plant is known from DE 33 37 739 A1. This continuous casting plant has a device for holding and changing ladles (ladle turntable), ladles, and a distribution trough, as well as a continuous casting mold and a strand discharge device. A distribution trough is associated with the molten-filled ladle, which is in the preparation position for transport to the casting position, for transport together with it. Preferably, in this embodiment, the distribution trough is inserted into the boom on the ladle turntable below the ladle, which is provided for receiving the ladle. The distribution trough and / or ladle are provided with means for detachable connection to each other.

[0008] From EP 0 119 853 A2 a distributor trough for continuous casting is known, wherein the distributor trough has a channeled induction heating device arranged on the side wall of the distributor trough, the device comprising a channel that communicates with an opening in the side walls of the distributor trough.

[0009] From EP 0 140 217 A1 a method and a device for changing the casting ladle and intermediate container on a continuous casting plant are known.

[0010] From EP 0 726 115 A1, a casting trough for receiving and filtering molten ferrous metals is known, which has a discharge opening in the bottom area for drawing off the molten metal after it has passed through a deflecting and / or filtering device. A ceramic filter, which covers substantially the entire horizontal cross-section of the casting trough and is removable in a known manner, is arranged in the trough. This filter extends substantially horizontally and is provided with openings arranged in the substantially vertical direction of flow of the molten metal through the trough. This is intended to enable the cleaning and filtering of molten metals, even at high casting speeds, with a simple design.

[0011] From EP 0 804 306 B1, a device for regulating the flow of molten metal in a distribution trough to improve the separation of inclusions from the metal bath is known. For this purpose, a flow control dam is positioned downstream of a shock buffer. This dam has an upper section designed to receive a flow of molten steel that detaches from the shock buffer and to divert it into at least one secondary flow flowing downstream towards the slag cover and at least one secondary flow flowing upstream towards the slag cover. Ultimately, this is an integrated dam intended to prevent short-circuit flow.

[0012] US Patent 6,074,600 discloses a modification of a distribution channel dam for minimizing turbulence. In particular, this is intended to reduce the formation of gas bubbles and slag inclusions. This is especially advantageous during the initial filling of the distribution channel. For this purpose, a weir is arranged between the steel inlet and outlet of the distribution channel, extending from the bath surface to the bottom but spaced apart from it. A ramp is arranged between the weir and the outlet, while a second ramp is located upstream of the weir.

[0013] From DE 10 2009 009 740 A1, it is known to arrange vortex stones in the area of ​​the bottom outlets of vessels containing molten steel in such a way that their knife edges extend into the vortex in order to prevent turbulence. The vortex stones consist of a circular segment-shaped flat fixing part and a braking part with the knife edge, whereby this one-piece component can be placed on the bottom outlet or, better yet, on a perforated stone and connected to it, because the inner diameter corresponds to that of the bottom outlet.

[0014] EP 3 496 882 B1 discloses a baffle plate for placement in a distributor to reduce the effects of a misalignment of an incoming stream of molten steel entering the distributor.

[0015] Furthermore, it is known to equip distribution channels with a bottom depression from the steel inlet to the steel outlet, whereby a ridge or raised section is placed on this sloping bottom, which is sometimes also stepped, such that the steel inlet area forms a kind of basin. After the basin is filled, the water flows over the ridge and then fills the entire distribution channel. This ridge also serves to ensure turbulent flow and to slightly extend the residence time of the steel in the distributor, and in particular to achieve contact with the slag layer.

[0016] From CN 103 25 465 B1 a so-called turbulent flow controller for asymmetric use in the distributor is known, in which the shadow tube is arranged above this installation, wherein this installation is arranged in a saucer-like shape with a slightly raised bottom on one side next to other waves in the distributor.

[0017] A comparable installation is known from CN 102 000 791 A, which is arranged below the shadow pipe and is located next to two ridges in the base of the distributor. However, in this case, the base of this installation, which has a cuboid shape, is corrugated, with the steel from the shadow pipe being poured into this structure and then exiting it from above.

[0018] From KR 2003 00 52 756 A, an installation is known which is arranged in a trough shape with its own vertical walls within the distributor, wherein the shadow pipe opens into a spring-like projection and from there the steel initially fills this trough-like structure before flowing into the rest of the distributor. The basic shape of the installation is approximately T-shaped, with the steel flowing into the rest of the T-shaped sub-distributor through a reduced opening.

[0019] A comparable installation is known from EP 0 804 306 B1, in which the steel is first poured into a trough located at ground level, then exits laterally and meets conventional wall installations.

[0020] A similar trough-like installation is also known from CN 217 121 721 U, in which, however, the trough is more elongated-oval in shape, but also with a wave-shaped bottom structure, so that the steel is first poured into this trough and then flows out of it into the rest of the distributor.

[0021] From “Numerical and Physical Study on New Simple Design of Subflux Flow Controller for One-Strand Tundish”, Cwudziński, Adam; Materials 2022, 15, 3756 ff., the influence on the flow using an asymmetric shadow tube has been investigated, simulating various arrangements.

[0022] From “Physical and mathematical modeling of inclusion behaviour in a tundish with gas curtain”; Metallurgy and Materials 2020, 73(4), 531 - 538, the influence of gas curtains in the inlet area was investigated, whereby the inlet area was additionally designed with walls hanging from above and walls rising from below.

[0023] It was found that all these measures either calm the flow of the liquid melt, but then lead to a shorter residence time, or make it so turbulent that the particle loading is high.

[0024] The object of the invention is to create a method for casting steel that simplifies distribution management, increases the separation sharpness between the batches to be cast, and reduces the mixing range.

[0025] The problem is solved by a method having the features of claim 1.

[0026] Advantageous further training courses are marked in the sub-requirements.

[0027] The invention is based on a number of insights.

[0028] In continuous casting, different batches of steel are cast continuously. After passing through the converter, each batch of steel is poured into a ladle and undergoes secondary metallurgical treatment.

[0029] To ensure a virtually uninterrupted continuous casting process, the contents of the ladle are poured into a distributor, which, however, still contains steel from the previous ladle. This is unavoidable, as otherwise the casting strand would break. The steel from the previous ladle is also referred to as the pre-melt, and the ladle that is subsequently filled into the distributor is called the post-melt.

[0030] Using multiple distributors would be extremely expensive. Therefore, the goal is to feed different steel grades through a single distributor one after the other.

[0031] According to the invention, the method is also intended to allow different grades of steel from different origins to be cast together using a distributor.

[0032] In particular, the invention is intended for casting steel grades produced using different methods, namely batches from the electric arc furnace (EAF) and batches from the conventional blast furnace (LD) route. These batches also exhibit, among other things, different CO2 footprints, which should be readily traceable within the context of a material's CO2 balance. However, the invention is also applicable to other steel grades, as it specifically takes into account the metallurgy of the melts.

[0033] Distribution planning (distribution management) is established well in advance. Therefore, a single distributor change for EAF or LD batches is hardly feasible.

[0034] Generally, when different steel grades are used in the subsequent casting strand and thus also in the slab, mixed areas will occur. With small differences in steel grade, this may be tolerable; otherwise, the mixed area is cut out and scrapped. A metallurgical analysis of the mixed area can also be used as a tracer for the CO2 balance.

[0035] To quantify the deviation of the respective melts from one another, the melt difference index (MDI) can be used. The MDI is calculated from the absolute deviations of individual elements between the melts (|ΔE). i |), which is combined with an element-specific weighting factor (k i ) is weighted, formed. The weighted deviation of an element (|ΔE i |* k i ) is calculated as the product of the absolute deviation (|ΔE i |) and the weighting factor (k i ).

[0036] In a preferred embodiment, the melt difference index (SDKZ) can be derived from the dn weighted deviations (|ΔE). i |* k i ) are ordered in descending order, the resulting series being called the ranking (rank). The ranking (rank) preferably includes all weighted deviations (|ΔE i |* k i ). A distinction must be made between the counter for the elements (i) and the counter for the ranking (j). Rangj=|ΔEi|⋅ki where Rangj>Rankj+1 Rank={Rank1,...,Rangj,Rangj+1,...,Rangn}

[0037] To determine the melt variation index (MSI), a defined number (x) of the largest weighted deviations can be included. For example, all elements can be included, or the selection can be limited to the three or five largest weighted deviations. The number (x) is chosen based on the process requirements. Advantageously, when all elements are included, the total MSI can be determined. In an alternative embodiment, when selecting the three or five largest deviations, the focus can be advantageously placed on the deviations of the most significant influencing factors, while other, comparatively minor (less effective) deviations are filtered out.This means that a melt which has very small deviations in numerous elements can be advantageously classified as less critical than a melt which only has deviations in three elements, but has comparatively large deviations in these three.

[0038] The largest weighted deviations (Rank 1, ... , Rank x The values ​​listed first in the ranking (rank) are shown below. The melting difference index (SDKZ) is calculated as follows. SDKZ=∑j=1xRankj

[0039] The more different the alloy compositions of the pre- and post-melt processes are, i.e., the larger the melt difference index (SDKZ), the more pronounced the mixing range.

[0040] The invention takes into account the varying differences of successively cast melts by adapting the charging of the melts in the distributor to the melt difference index (SDKZ). The inventors aimed to minimize the mixing range and increase the separation efficiency during continuous casting with different steel grades. This results in a reduced number of distributors required, as it becomes possible to cast different steel grades using the same distributor.

[0041] An optimized manifold management system for continuous casting with different steel batches, minimizing the need for manifold changes, results in cost reductions, as fewer of the very expensive manifolds are required, as well as a reduction in the workload during the continuous casting process.

[0042] Continuous analyses are performed at the distributor to indicate the beginning and end of the mixing zone. These analyses specifically show when the first batch (pre-melt) is still present at the discharge end of the continuous casting distributor, when thorough mixing has occurred, and when the second batch (post-melt) is present. This data can be used to control the slab cutting process, reliably removing the mixing zone from the casting strand.

[0043] This is expected to become even more important in the future, as conventional steel production in converters, involving the refining of a mixture of scrap and pig iron and the transfer of this crude steel into a ladle (LD steel), could be replaced by electric arc furnaces and upstream direct reduction (EAF steel). This will lead to frequent switching between LD and EAF batches in the continuous casting process.

[0044] However, it is also important to note that the successively cast melts must not differ too much in terms of their alloy composition, as otherwise various difficulties, such as hot cracks, poor butt joints, different liquidus temperatures, etc., may occur.

[0045] Critical elements, where problems can arise if there are significant differences between melts, include carbon, aluminum, niobium, vanadium, zirconium, boron, and nitrogen. Silicon, manganese, copper, titanium, chromium, nickel, and molybdenum, on the other hand, are comparatively uncritical.

[0046] The invention thus relates in particular to a method for continuous casting of metal, especially steel, wherein liquid metal from a ladle, which is movably mounted, is directed by means of a shadow pipe into a continuous casting manifold and from the continuous casting manifold is directed via an outlet into a casting mold, wherein the continuous casting manifold compensates for the interruptions when the ladles are changed, and wherein the ladles are mounted in a moving device, wherein different melts with respect to their alloy composition and origin are cast successively into the manifold, wherein the successively cast, different melts are LD melts on the one hand and EAF melts on the other.

[0047] One embodiment provides that the absolute deviations of the respective alloying elements |ΔE Zul,i |, preferably |ΔE Bev,i |, especially preferred |ΔE BBev,i| the different melts may have the following maximum values ​​compared to each other: jeweils in Gew.% Absolute deviations of individual elements between the melts |ΔE i | Element Permissible |ΔE Zul,i | Preferred |ΔE Bev,i | Especially preferred|ΔE BBev,i | C 0,25 0,20 0,10 Si 0,40 0,30 0,25 Mn 1,00 0,80 0,70 Al 0,15 0,10 0,09 Nb 0,15 0,10 0,07 Cu 0,50 0,40 0,35 Ti 0,40 0,30 0,15 V 0,15 0,10 0,07 Cr 0,50 0,40 0,35 Ni 0,40 0,30 0,25 Mo 0,40 0,30 0,25 Zr 0,15 0,10 0,05 B 0,05 0,03 0,02 N 0,02 0,01 0,008

[0048] One embodiment provides that deviations in the melts (ΔEi) are quantified with a melt difference index (SDKZ), wherein the melt difference index (SDKZ) is formed from the absolute deviations of individual elements between the melts |ΔEi|, which is weighted with an empirically determined element-specific weighting factor (ki), wherein the weighted deviation of an element (|ΔEi|* ki) is formed from the product of the absolute deviation (|ΔEi|) and the weighting factor ki.

[0049] One embodiment provides that the empirically determined element-specific weighting factors (ki) have the following values: Element Weighting factor k i C 0,40 Si 0,25 Mn 0,10 Al 0,67 Nb 0,67 Cu 0,20 Ti 0,25 V 0,67 Cr 0,20 Ni 0,25 Mo 0,25 Zr 0,67 B 2,00 N 5,00

[0050] One embodiment provides that the weighted deviations |ΔEi|* ki are ordered in descending order, the resulting series being called the ranking or rank, the ranking or rank comprising all weighted deviations |ΔEi|* ki, the following relationship between the numerator for the elements (i) and the numerator for the ranking (j) holds: Rangj=|ΔEi|⋅ki where Rangj>Rankj+1 Rank={Rank1,...,Rangj,Rangj+1,...,Rangn}

[0051] One embodiment provides that the melt difference index (SDKZ) is formed from the largest weighted deviations, where x defines a defined number of the largest weighted deviations, wherein: SDKZ=∑j=1xRankj

[0052] One embodiment provides that x >= 1 preferably x >= 3, particularly preferably x >= 7, especially x = 14.

[0053] One embodiment provides that the melt difference index (SDKZ) is divided into three categories, namely in permissible SDKZ Zul , preferably SDKZ Bev , and especially preferred SDKZ BBEV where the values ​​of the three categories are derived from the product of constant melt difference index change (SDKZ'), permissible SDKZ' Zul , preferably SDKZ' Bev , especially preferred SDKZ' BBev , and the number of largest weighted deviations (x), where: SDKZZul=SDKZZul'⋅x SDKZBev=SDKZBev'⋅x SDKZBBev=SDKZBBev'⋅x

[0054] One embodiment provides that the constant melt differential index change (SDKZ') is permissible SDKZ' Zul , preferably SDKZ' Bev , especially preferred SDKZ' BBev , exhibit the following values: Permissible SDKZ' Zul Preferably SDKZ' Bev SDKZ' is especially preferred BBev SDKZ' 0,10 0,07 0,05

[0055] One embodiment provides that the sequential filling of the distributor with the two different melts is adapted to the melt difference index (SDKZ), whereby no adjustment in the distributor is required if the melt difference index (SDKZ) is less than the limit value for the particularly preferred melt difference index (SDKZ). BBev ) is, wherein, for a melt difference index (SDKZ), there is a difference between the limit values ​​for the particularly preferred melt difference index (SDKZ). BBev ) and for the preferred melt difference index (SDKZ) Bev ) Adjustments are made in the distributor so that the ratio of remelt to premelt in the distributor is greater than 1.5 to 1, and wherein a melt difference index (SDKZ) exists between the limit values ​​for the preferred melt difference index (SDKZ). Bev ) and permissible melt difference index (SDKZ) Zul) Adjustments must be made in the distributor so that the ratio of post-melt to pre-melt in the distributor is more than 2 to 1.

[0056] With these defined limit values ​​for the melt difference index (SDKZ) Zul , SDKZ Bev , SDKZ BBe A distinction can be made between permissible, preferred, and particularly preferred ranges. Instructions for action are defined for each range. The limit values ​​for the melt differential index (SDKZ) Zul , SDKZ Bev , SDKZ BBe ) can result from the product of constant melt difference index changes (SDKZ') Zul , SDKZ' Bev , SDKZ' BBev ) and the number (x) of largest weighted deviations. SDKZZul=SDKZZul'⋅x SDKZBev=SDKZBev'⋅x SDKZBBev=SDKZBBev'⋅x

[0057] Is the melt difference index (SDKZ) smaller than the limit value for the particularly preferred melt difference index (SDKZ) BBev These melts can be cast together in the distributor without any adjustments. SDKZ≤SDKZBBev→No adjustment

[0058] Is the melt difference index (SDKZ) greater than the limit value for the particularly preferred melt difference index (SDKZ) BBev ) and less than or equal to the limit value for the preferred melt difference index (SDKZ) Bev ), a distributor adjustment can advantageously be made such that the ratio of remelt to premelt is more than 1.5:1 in the distributor, this can advantageously reduce the mixing area. SDKZBBev <SDKZ≤SDKZBev→Verteileranpassung 1,5:1

[0059] Is the melt difference index (SDKZ) greater than the limit value for the preferred melt difference index (SDKZ)Bev ) and less than or equal to the limit value for the permissible melt difference index (SDKZ) Zul ), a distributor adjustment can advantageously be made such that the ratio of remelt to premelt is more than 2:1 in the distributor; this can advantageously reduce the mixing area even further. SDKZBez <SDKZ≤SDKZZul→Verteileranpassung 2:1

[0060] Is the melt difference index (SDKZ) greater than the permissible melt difference index (SDKZ) Zul ) and / or individual elements differ too much in their absolute deviations. Thus, the differences between the various melts may be deemed too large, and the melts may be classified as unsuitable, i.e., not permissible, for the process. SDKZZul <SDKZ→Nicht zula¨ssig

[0061] One embodiment provides that when determining a value of a) Absolute deviations of individual elements between melts |ΔE i | of one or more elements above the limit allowed |ΔEZul,i| and / or b) an SDKZ above the limit permissible SDKZ Zul , a sequential filling of the distributor with the two different melts is not carried out.

[0062] The invention is explained by way of example with the aid of a drawing. The drawing shows: Fig. 1: Highly schematic representation of a continuous casting plant; Fig. 2: a table showing the maximum analytical difference between successive batches; Fig. 3: a table showing the element-specific factor (ki) of the individual element contents for determining the melting difference index (SDKZ); Fig. 4: a table showing pre-melting and post-melting, which cannot be mixed due to excessive deviations; Fig. 5: a table showing pre- and post-melts whose melt difference index was determined with 14 largest weighted deviations (x=14) and the determined melt difference index corresponds to a particularly preferred range; Fig. 6: a table showing pre- and post-melts whose melt difference index was determined with 8 largest weighted deviations (x=8) and the determined melt difference index corresponds to a preferred range; Fig. 7: a table showing pre- and post-melting, whose melt difference index was determined with 5 largest weighted deviations (x=5) and the determined melt difference index corresponds to a permissible range; Fig. 8: a table showing the individual melt difference index changes for the calculation of the limit values ​​of permissible, preferred and particularly preferred melt difference indexes; Fig. 9: a diagram showing the progression of limit values ​​of permissible, preferred and particularly preferred melt difference parameters over the number of largest weighted deviations considered, and in which the determined melt difference parameters of the examples according to Fig. 6, Fig. 7 and Fig. 8 are applied; Fig. 10: highly schematic two batches in a distributor, where the feed of the second batch depends on the degree of runoff of the first batch and the ratio of the two batches to each other (post-melt to pre-melt) is greater than 1.5 to 1 with a melt difference index of 0.2 to 0.5; Fig. 11: highly schematic two batches in a distributor, where the feed of the second batch depends on the degree of runoff of the first batch and the ratio of the two batches to each other (post-melt to pre-melt) is greater than 2 to 1 with a melt difference index of 0.5 to 1.4; Fig. 12: Highly schematic representation of a continuous casting plant showing the casting strand with pre-melting, mixing zone and post-melting. Fig. Figure 1 shows a highly schematic representation of a continuous casting plant 1. This plant has a first metallurgical vessel 2, for example a ladle 2, containing liquid metal. Below this is a continuous casting distributor 3, which is loaded with liquid metal via a shadow pipe 4 attached to the ladle 2. The shadow pipe 4 can have one or more outlet openings. The distributor 3 is an elongated, preferably trough-like container with two opposing end walls 5, 6 and two side walls 7, 8 connecting the end walls 5, 6.

[0063] Furthermore, the continuous casting manifold 3 has a base 9, with an inlet area 11 and an outlet area 12 provided along a central axis of the manifold 3. The inlet area 11 is located adjacent to an inlet-side end wall 5, while the outlet area 12 is located adjacent to an outlet-side end wall 6, so that, in principle, the incoming steel flows through the vessel following the longitudinal extent of the continuous casting manifold 3. However, the continuous casting manifold 3 can also be shaped differently, for example, V-shaped or with multiple fingers or multiple outlets.

[0064] The bottom 9 of the continuous casting distributor 3 can slope downwards from an inlet area 11 to an outlet area 12, where sloped means that the depth becomes deeper relative to a bath level 13.

[0065] In the discharge area 12, a discharge 14 with a casting pipe 15 is arranged in the base 9. The casting pipe 15 opens into a mold 16, in which the metal is cooled until it solidifies. The strand 17 emerges from the bottom of the mold 16, is deflected by means of refractory rollers 18, and enters a straightening zone 19. After the straightening zone 19, the strand 17 is cut into slabs 21 by means of flame cutters 20.

[0066] In the continuous casting of metal, especially steel, in such a continuous casting plant 1, liquid metal is conveyed from the ladle 2, which is movably mounted, via the shadow pipe 4 into the continuous casting manifold 3 and from the continuous casting manifold 3 via the outlet 14 into the casting mold 16. The continuous casting manifold 3 compensates for interruptions when the ladles 2, which are mounted in a moving mechanism, are changed.

[0067] According to the invention, in such a continuous casting plant 1, different grades of steel with respect to their alloy composition and origin are to be cast successively in the same distributor 3. The deviation of the respective melts from one another can be quantified by the melt difference index SDKZ, and the sequential filling of the distributor 3 with the two batches is adapted to the melt difference index.

[0068] When two different steel grades, for example, from different origins such as LD and EAF batches, are cast successively in a distributor, certain maximum permissible differences in analysis regarding the individual alloying elements must be observed. These are specified in Fig. 2. Presented in tabular form.

[0069] The melt difference index (SDKZ) is calculated using the deviations of the individual alloying elements between the pre- and post-melt (ΔE). i) multiplied by an empirically determined, element-specific factor (k i ), ordered in descending order to a ranking (rank) and the defined number (x) of the first (=largest) weighted deviations summed: Rangj=|ΔEi|⋅ki where Rangj>Rankj+1 Rank={Rank1,...,Rangj,Rangj+1,...,Rangn} SDKZ=∑j=1xRankj

[0070] Fig. Figure 3 shows the corresponding empirically determined factors for the individual alloying elements in tabular form. Based on the factors that weight the deviations of the individual alloying elements, it becomes clear that the elements carbon, aluminum, niobium, vanadium, zirconium, boron, and nitrogen are particularly critical for determining the melting point differential, as their factors are comparatively high. In contrast, the elements silicon, manganese, copper, titanium, chromium, nickel, and molybdenum are comparatively less critical, as their respective factors are relatively low.

[0071] To illustrate the calculation of the melt difference index, it was calculated as an example for an LD premelt and an EAF postmelt ( Fig. 4, Fig. 5, Fig. 6 and Fig. 7) Naturally, these values ​​would also apply if the EAF melt had been the pre-melt and the LD melt the post-melt. The deviations in the alloy composition with respect to the individual alloying elements, as well as the element-specific factors, are factored out. Fig. 3 one.

[0072] Fig. Figure 4 shows a pre- and post-melt where the absolute deviation of the aluminum content exceeds the maximum permissible value of 0.150 wt.%, which is 0.240 wt.%. These melts cannot be cast consecutively. Calculating the melt difference index is not necessary.

[0073] Fig. Figure 5 shows a pre- and post-melt cycle in which all elemental contents comply with the respective permissible absolute deviations. For the calculation of the melt difference index, the absolute deviations of the elemental contents were multiplied by the weighting factor ( Fig. 3) multiplied and ranked. In this example, 14 deviations, i.e., x = 14 of the element contents, were taken into account. The melting point difference index of 0.189 corresponds to a particularly favored range ( Fig. 9) since these exceed the limit of SDKZ B-BEV significantly below 0.70.

[0074] Fig. Figure 6 shows a pre- and post-melt process in which all elemental contents comply with the respective permissible absolute deviations. The calculation of the absolute weighted deviations is performed in the same way as for the example in [reference]. Fig. 5. In this example, 8 deviations (x=8) of the elemental contents were considered. The melt difference index of 0.430 corresponds to a preferred range ( Fig. 9) since the SDKZ BBEV a limit of 0.40 is specified and this is exceeded, but the value of SDKZ BEV The value falls below 0.56.

[0075] Fig. Figure 7 shows a pre- and post-melt process in which all elemental contents comply with the respective permissible absolute deviations. The calculation of the absolute weighted deviations is performed in the same way as for the example in [reference]. Fig. 5. In this example, 5 deviations (x=5) of the elemental contents were taken into account. The melt difference index of 0.416 corresponds to a permissible range ( Fig. 9), since the values ​​of SDKZ eeεv (0.25) and SDKZ BEV (0.35) each exceeded, but the value of SDKZ ZUL (0.50) is undercut.

[0076] In general, the melt difference index (SDKZ) depends on the number of the largest weighted deviations (x). Limit values ​​for the melt difference index (SDKZ) Zul , SDKZ Bev , SDKZ BBe A distinction is made between permissible, preferred and especially preferred areas ( Fig. 9) To calculate the limit values, constant changes in melt difference indicators are multiplied by the number of the largest weighted deviations. Fig. Figure 8 shows the constant changes in the melt difference index for the individual areas.

[0077] Are the batches to be cast successively very similar in their composition (SDKZ ≤ SDKZ)? BBev ), no specific adjustments are required in the manifold, and the batches can simply be cast one after the other in the same manifold without adverse effects such as hot cracking, poor butt joints, or different liquidus temperatures being expected in the resulting slab. The melt differential coefficient (SDKZ) is in the particularly preferred range ( Fig. 9).

[0078] However, if the melt difference index lies between the limit values ​​for the particularly preferred melt difference index SDKZ BBevand for the permissible melt difference index SDKZ Zul Additional measures must be taken to avoid any problems arising from differences in steel batches and to prevent the need for a change of distributor. Advantageously, a specific ratio of remelt to premelt should be set, adapted to the melt difference index ( Fig. 9). This can be achieved, for example, by temporarily closing the pouring tube 15 with a plug 22 ( Fig. 10 and Fig. 11).

[0079] In the case of a melt difference index between the limit values ​​for the particularly preferred melt difference index SDKZ BBev and the limit values ​​for the preferred melt difference index SDKZ Bev Adjustments will be made in distributor 3 so that a ratio of remelting to premelting of more than 1.5 to 1 is set in distributor 3 ( Fig. 10) The melt differential index (SDKZ) is in the preferred range ( Fig. 9).

[0080] In the case of a melt difference index between the limit values ​​for the preferred melt difference index SDKZ Bev and the limit values ​​for the permissible melt difference index SDKZ Zul Adjustments will be made in distributor 3 so that a ratio of remelting to premelting of more than 2 to 1 is set in distributor 3 ( Fig. 11) The melt differential index (SDKZ) is within the permissible range ( Fig. 9).

[0081] In Fig. Figure 12 shows the use of one and the same distributor 3 for different batches, for example LD and EAF melts, in a continuous casting plant 1, which forms a casting strand 17 with a mixing zone, shown schematically.

[0082] The measures according to the invention allow the different steel batches to be cast in one and the same manifold with high separation efficiency and a reduced mixing range. This simplifies manifold management and contributes to reducing the overall process costs, as fewer of the very expensive manifolds are required. Reference symbol list 1 continuous casting plant 2 metallurgical vessel / pan 3 continuous cast manifolds 4 shadow tube 5 End wall 6 Front wall 7 side wall 8 side wall 9 distributor floor 11 Inlet area 12 Outlet area 13 bathroom mirrors 14 outlet 15 Watering pipe 16 molds 17 strand 18 fireproof rollers 19 Guideline zone 20 oxyfuel cutters 21 slabs 22 plugs QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 33 37 739 A1

[0007] EP 0 119 853 A2

[0008] EP 0 140 217 A1

[0009] EP 0 726 115 A1

[0010] EP 0 804 306 B1 [0011, 0019] US 6,074,600

[0012] DE 10 2009 009 740 A1

[0013] EP 3 496 882 B1

[0014] CN 103 25 465 B1

[0016] CN 102 000 791 A

[0017] KR 2003 00 52 756 A

[0018] CN 217 121 721 U

[0020]

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