EP3427863A1 - Method and system for the production of cast blocks from metal - Google Patents

Abstract

The invention relates to a method for producing cast blocks (5) from metal (1), in particular from steel with alloy constituents, by continuous casting from a ladle (10) or from a ladle (10) via an intermediate vessel (12) into a short, after Open mold at the bottom (14) and removal of the strand (4) from the mold (14) by means of a take-off device (22; 22a), in which the strand (4) is not deformed in the longitudinal direction.

Description

State of the art

The invention relates to a method for producing cast blocks from metal, in particular from steel with alloy components, according to the preamble of claim 1. Furthermore, the invention relates to a system for carrying out the method according to the invention.

A method for the production of cast blocks from metal with the features of the preamble of claim 1 is known from WO 2015/101553 A1 the applicant known. The process, also known as continuous casting, is a process that has been known and tested for decades and represents a standard for the production of cast blocks of various qualities and dimensions. In continuous casting, there are applications in which the liquefied metal is not produced directly from the ladle but by using a Taken between intermediate ladle between the ladle and the mold in the mold or poured. Furthermore, the continuous casting process known from the prior art, depending on the format (in this case, the cross-sectional area of the cast block), is characterized by casting or block formation rates of between 0.3 m / min and 4 m / min. This typically results in metallurgical lengths in the ingot or strand of usually at least 15m to 25m and even longer. In this case, the metallurgical length is understood to be the length in the cast block, in the region of which the liquefied metal has not yet completely solidified over the cross section of the cast block. In particular, such continuous casting process are characterized by the fact that they have a high Enables productivity even with large volumes of steel to process, typically between 100,000 tonnes and 300,000 tonnes per strand per year.

In addition to the above-mentioned continuous casting process with all its technical variants and depending on the application existing features there is also still the block casting process in which the liquefied metal is poured into a closed in the bottom region vessel, which is removed after solidification of the strand of the strand. The ingot casting method is especially applied to special grades, i. in compositions of the strand or ingot, for which there is typically only a relatively small need, for example, high-alloy steels. For such small amounts, the continuous casting process required above for producing the continuous casting process is not worthwhile, because it requires a relatively high technical complexity, in particular through extraction devices for removing the strand from the mold, deflection for transferring the strand produced in vertical continuous casting in a horizontal direction etc.

Furthermore, it is mentioned that it is not possible for quality reasons in cast blocks, for example made of high-alloy steels to reduce the height of a continuous casting plant to redirect them from the vertical to the horizontal, as this strength or quality-reducing stresses are generated in the cross section of the solidified strand. Although such strands can be produced in a continuous casting process via a vertical casting process, this inevitably leads to very high construction heights of the continuous casting plant, which are associated with a very high capital outlay. However, as explained above, such investment costs are typically not worthwhile for the special steels produced in relatively small quantities.

Furthermore, the block casting process is also suitable if the required dimensions of the strand are very large, so that this would lead to extreme machine lengths and investment costs in the case of continuous casting production at the usual continuous casting speeds and casting times.

As disadvantageous in the production of strands in the block casting process u.a. the relatively long manual preparation times, the low yield (i.e., the relatively small amount of molten metal that can be used for billet casting in the total amount of molten metal) and the only average quality of the block exhibited.

Disclosure of the invention

Based on the illustrated prior art, the present invention seeks to design a known from the prior art continuous casting process such that it is suitable to produce ingots of metals, which typically for the reasons mentioned above, only economically over make the ingot casting process or where the skilled person would typically use the ingot casting process. In particular, it is an object of the invention to design the continuous casting process in such a way that, compared to the ingot casting method, no reduced quality of the ingot produced from the liquefied metal has to be accepted, and furthermore that the process enables plants that can be produced with relatively low investment costs thus to be able to produce cast blocks economically even with relatively low production quantities.

The above objects are achieved according to the invention in a method for producing cast ingots made of metal with the features of claim 1 by a precisely coordinated selection of parameters that must be met during the manufacture of cast blocks in the continuous casting process.

Essential to the invention is that a casting rate from the ladle or the intermediate vessel in the mold between 50kg / min and a maximum of 300kg / min is set, that the ladle is heated, that the temperature of the metal in the ladle during the entire casting process to a target Temperature is controlled with a temperature tolerance of ± 5 ° C, that the target temperature at the beginning of the casting process is a maximum of 30 ° C above the melting point of the metal to be cast, and that the metallurgical length of the strand is a maximum of 15m. Due to the precise temperature control, the casting speed can be chosen to be relatively small, which has a positive effect on the quality of the cast ingot or strand produced.

By adhering to the combination of the claimed parameters with the mentioned limits cast blocks made of metal, in particular of steel with alloy constituents, can be produced in the continuous casting process, which have no loss of quality compared to ingots produced in the block casting process and moreover an economical production allow even at relatively low levels, since on the one hand the output is massively increased compared to the block casting process and at the same time the investment costs for a required for the manufacture of such ingots plant can be limited.

Advantageous developments of the method according to the invention are listed in the subclaims. All combinations of at least two features disclosed in the claims, the description and / or the figures fall within the scope of the invention

As explained above, the method according to the invention is particularly suitable for producing cast blocks made of metal, which use steel with alloy components, so that special qualities are produced due to the alloy constituents, for example particularly high or good strength properties or similar properties desired depending on the alloy constituents respectively. In particular, steels are used in which chromium, nickel, molybdenum or tungsten are added individually or in combination as alloy constituents, with the proportion by weight of the total alloy constituents typically being at most 30%. In addition, the inventive method is also suitable for the production of nickel and / or cobalt superalloys with nickel and cobalt contents of over 50%.

In order to avoid the use of an intermediate vessel between the ladle and the mold that the (liquefied) metal in the tundish, especially after emptying the ladle to cool down too much before it is poured into the mold, it is in embodiments in which an intermediate vessel is used, provided that this has a maximum of 20% of the volume of the ladle, wherein the metal is not heated in the region of the tundish. Due to the relatively small intermediate vessel is thus excluded that too much heat loss or excessive cooling of the metal takes place in the tundish, which would otherwise only an additional increased target temperature for the metal in the ladle could be compensated, which, however, in turn, among other things, for reasons of energy consumption and quality reasons is not desirable.

However, if an intermediate vessel is to be used whose volume is between 20% and 100% of the ladle volume, it is envisaged to produce high quality ingots from the above discussion that the tundish is heated, either alternatively to heating the metal in the ladle for single casting or additionally for sequence casting.

It is most preferred if the process leads to metallurgical lengths in the strand between at least 2m and a maximum of 10m. With such orders of magnitude of the metallurgical length, the desired qualities can be produced particularly easily and well with relatively compact systems.

As explained at the outset, it is provided according to the invention to adhere to very specific casting parameters for producing the desired qualities in the economic production of the cast blocks. In addition, the essential parameters explained in the context of the invention can be additionally specified or optimized and supplemented. This includes that the casting time for emptying the metal from the ladle is at least 70 minutes. In other words, this means that compared to typical continuous casting processes, the casting time tends to be rather long, ie, there is a tendency for slower pouring of the metal from the ladle into the mold compared to typical continuous casting processes. This slow potting favors the optimization of the quality of the casting.

Furthermore, the invention also includes a system for carrying out a method according to the invention described so far with a ladle, a mold and a discharge device for removing an at least partially solidified strand from the mold. Due to the procedural parameters provided such a system is typically characterized by the fact that their total height is a maximum of 40m. As a result, the investment costs for the system, which in addition to the costs for the actual system also include building investment costs, significantly limit or significantly reduce.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing.

Fig. 1

eine erste Anlage zur Herstellung von Gussblöcken aus Metall im Stranggussverfahren unter Verwendung einer absenkbaren Bodenplatte in einer vereinfachter Darstellung und

Fig. 2

eine gegenüber Fig. 1 modifizierte Anlage mit einer kontinuierlichen Abzugseinrichtung und mit einer Trenneinrichtung zum Abtrennen erstarrter Gussblöcke von einem Strang zum kontinuierlichen Vergießen und inline-Abtrennen einer vordefinierten, frei wählbaren Stranglänge mit der Möglichkeit, mehrere Gießpfannen hintereinander ohne Unterbrechung des Gießvorgangs vergießen zu können..

This shows in

Fig. 1

a first plant for the production of cast ingots from metal in the continuous casting process using a lowerable bottom plate in a simplified representation and

Fig. 2

one opposite Fig. 1 modified plant with a continuous extraction device and with a separator for separating solidified ingots from a strand for continuous casting and inline separation of a predefined, freely selectable strand length with the ability to shed several ladles in a row without interrupting the casting ..

The same elements or elements with the same function are provided in the figures with the same reference numerals.

In the Fig. 1 a simplified first system 100 for carrying out the method according to the invention is shown schematically simplified during the regular casting process of a strand 4. The liquid metal 1 contained in a masonry ladle 10 typically consists of steel with alloying constituents, in particular chromium, nickel, molybdenum or tungsten, individually or in combination, the weight proportions of the alloy constituents totaling a maximum of 30%. The ladle 10 is designed as a heated ladle 10 and arranged in operative connection with a heating device 11, which is shown only symbolically and is known per se from the state of the art. The heating device 11 may in particular be an inductive heating device 11, a heating device 11 using two or three graphite or hollow electrodes with or without gas supply or a plasma torch.

The metal 1 passes through a likewise lined intermediate vessel 12 in a short, water-cooled oscillating and downwardly open mold 14, which may be provided with a Kokillenrührer 16, in the liquid metal sump 3, which is enclosed by the forming solidified strand shell of a cast block 5 ,

In the event that the volume of the tundish 12 is at most 20% of the volume of the ladle 10, the tundish 12 is typically provided without a heating device. However, if the volume of the intermediate vessel 12 is between 20% and 100% of the volume of the ladle 10 or of the metal 1 located within the ladle 10, then it is preferably provided that the intermediate vessel 12 is provided in a heating device not shown in the FIGURE or is heated. Such a heating device can then be designed, for example, as induction heating or with two or three graphite or hollow electrodes. It also explains that it is also possible the metal supply to the mold 14 to be made directly from the ladle 10, ie to dispense with an intermediate vessel 12. To protect against oxidation, the liquid metal 1 is discharged through so-called ceramic shadow tubes 18 into the tundish 12 or the mold 14.

The metal mirror in the vertically oriented mold 14 is usually covered by casting powder 7. The resting on a bottom plate 20 with a trigger mechanism 22, forming ingot 5 of the strand 4 is withdrawn according to the casting speed down so long from the mold 14 until the desired or due to the volume of the metal 1 in the ladle 10 resulting block length L is reached. There is no deformation of the strand 4 in the longitudinal direction of the strand 4 instead.

In addition to an optionally provided electromagnetic mold stirrer 16, it is also possible to provide an optionally vertically movable electromagnetic stirrer 24 below the mold 14 in the region of a secondary cooling zone 26 and also in the region of solidification of the cast block 5. Furthermore, one or more isolation devices may be provided below the mold 14 with horizontally movable against the cast block 5 can be placed or stationarily arranged warming bowls 25.

The total height H of the plant 100, starting from a foundation 101, is a maximum of 40m, not shown facilities of the plant 100 can be provided above the ladle 10.

Furthermore, the cast block 5 produced by the continuous casting method according to the invention is characterized by a metallurgical Length I of the metal sump 3 or the strand 4 between at least 2m and a maximum of 15m, with preferably a maximum of 10m are provided. The casting block 5 is withdrawn from the region of the mold 14 by means of the trigger mechanism 22 continuously in accordance with the casting speed of the metal 1 from the ladle 10 and from the tundish 12 into the mold 14. The casting time for casting the metal 1 in the ladle 10 is preferably at least 70 minutes, with a casting rate being set in the mold 14 per strand 4 between 50 kg / min and 300 kg / min, regardless of the casting format or cross section of the strand 4. Furthermore, it is provided that the temperature T of the metal 1 in the ladle 10 _is controlled to a temperature tolerance of +/- 5 ° C to a target temperature T _soll , which is made possible by the heated ladle 10. The target temperature T _soll is a preselected temperature, which is a maximum of 30 ° C above the melting point of the metal to be cast 1. For controlling the temperature T of the metal 1 in the ladle 10, a control device 30 can serve in particular, which performs a corresponding control of the heating device 11 as a function of the measured temperature T or is connected to the heating device 11.

By the above-mentioned process parameters and the dimensioning of the plant 100, special grades or ingots 5 can be economically produced in the continuous casting process, which are typically characterized by relatively high alloy constituents and by relatively low production quantities per year.

The in the Fig. 2 illustrated plant 100a is characterized in that instead of the bottom plate 20, a trigger mechanism 22a is used with take-off rollers 27, which pull the strand 4 from the mold 14. Furthermore, the forming ingot 5 of the strand 4 after its solidification by a suitable, vertically movable Separator 28 separated at the level of the dividing line 8 and transported away by means of a vertically movable transport or handling device 29 from the area of the plant 100a. This allows the implementation of the so-called sequence casting, in which the metal 1 can be processed or potted from several Gießpannen 10 in time immediately consecutive, without interrupting the casting process.

The system 100, 100a described so far, as well as the method described, moreover, should not be limited to the exemplary embodiment described, but may also contain modifications which, however, make use of the mentioned parameters during casting.

Thus, for example, it is conceivable to provide an existing heat-resistant material, possibly heatable compensating tank 35 in the system 100, 100a, which is placed in particular against pouring onto the mold 14, on the one hand to supply metal 1 as compensation for shrinkage and on the other hand, a delayed Solidification of the metal 1 in the mold 14 to effect, which again has a quality increasing effect.

LIST OF REFERENCE NUMBERS

1

metal

3

metal sump

4

strand

5

ingot

7

casting powder

8th

parting line

10

ladle

11

heater

12

intermediate vessel

14

mold

16

mold stirrers

18

Ladle

20

baseplate

22, 22a

trigger mechanism

24

stirrer

25

Hot tray

26

Secondary cooling zone

27

off roll

28

separator

29

handling device

30

control device

35

surge tank

100, 100a

investment

101

foundation

I

metallurgical length

L

block length

H

Height of the plant

Claims (11)

Method for producing cast blocks (5) from metal (1), in particular from steel with alloy constituents, by continuous casting from a ladle (10) or from a ladle (10) via an intermediate vessel (12) into a short, downwardly open mold ( 14) and removing the strand (4) from the mold (14) by means of a take-off device (22; 22a) in which the strand (4) is not deformed in the longitudinal direction,
characterized,
that a casting rate from the ladle (10) or from the tundish (12) from 50kg / min to 300kg / min is set, that the ladle (10) is heated, that the temperature (T) of the metal (1) in the Ladle (10) is controlled during the entire casting process to a target temperature (T _soll ) with a temperature tolerance of +/- 5 degrees Celsius that the target temperature (T _soll ) at the beginning of the casting process a maximum of 30 degrees above the melting point of the metal to be cast (1 ), and that the metallurgical length (I) of the strand (4) is at most 15m. Method according to claim 1,
characterized,
that the metal (1) is steel and that as alloy constituents chromium, nickel, molybdenum, tungsten, individually or in combination with a total weight fraction of max. 30% are used. Method according to claim 1 or 2,
characterized,
that when using an intermediate vessel (12) this has a maximum of 20% of the volume of the ladle (10), wherein the metal (1) in the region of the intermediate vessel (12) is not heated. Method according to claim 1 or 2,
characterized,
that when using a tundish (12) this has between 20% and 100% of the volume of the ladle (10), wherein the metal (1) in the region of the tundish (12) is heated. Method according to one of claims 1 to 4,
characterized,
that the strand (4) is withdrawn continuously from the mold (14). Method according to one of claims 1 to 5,
characterized,
that the metallurgical length (I) of the strand (4) is at least 2 m and not more than 10m. Method according to one of claims 1 to 6,
characterized,
that the pouring time of the emptying of the ladle (10) is at least 70min. Method according to one of claims 1 to 7,
characterized,
that a possibly heated compensating container (35) for receiving liquid metal (1) is placed on the mold (14) towards the end of the casting. Plant (100, 100a) for carrying out a method according to one of claims 1 to 8, comprising a pouring ladle (10), a mold (14) and a withdrawal device (22; 22a) for drawing off an at least partially solidified strand (4) from the Mold (14),
characterized,
that the total height (H) of the system (100) is a maximum of 40m. Plant according to claim 9,
characterized,
in that the ladle (10) is arranged in operative connection with a heating device (11), and in that the heating device (11) can be actuated by a control device (30) to maintain the setpoint temperature (T _soll ). Plant according to claim 9 or 10,
characterized,
in that a possibly heated compensating container (35) for liquid metal (1) is provided, which can be placed on the end of the mold (14) temporarily, in particular against the end of pouring.

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