GB1581069A

GB1581069A - Process for continuously casting steel in a continuous casting installation

Info

Publication number: GB1581069A
Application number: GB1161977A
Authority: GB
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1976-04-15
Filing date: 1977-03-18
Publication date: 1980-12-10
Also published as: JPS52126620A; FR2347998A1; ATA114577A; CA1077233A; IT1077791B; DE2617263A1

Description

(54) PROCESS FOR CONTINUOUSLY CASTING STEEL IN A CONTINUOUS CASTING INSTALLATION (71) We, MANNESMANN AI(TIEN GESELLSCHAFT, a joint stock company organised under the laws of Germany, of 4 Dusseldorf 1, Mannesmannufer 2, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - The invention relates to a process for continuously casting steel in a continuous casting apparatus.

It is known that, if a continuous casting has a small cross-section, the casting output of the casting channel is small. It may amount to a maximum of only 500 kg/min.

On the other hand, because of the fall in temperature of the steel in the casting ladle, the casting time for the contents of the ladles is limited. If it is desired to cast larger weights of melt as a continuous casting of small dimension, then it is necessary to use a large number of casting channels.

It is however not possible for the number of the channels to be arbitrarily increased, because as the number of the casting channels increases, the distance between the pouring location and the chill mould arranged furthest away (and hence the difference in temperature) exceeds permitted values. For a continuous casting apparatus having the largest possible number of casting channels, the maximum size of cast metal which can be produced has a small cross-section which is today still below the level possible in converter steel-making plants.

In order to increase the efficiency of continuous casting apparatus by sequential casting, it is necessary to have a strictly timed relationship between the steelmaking plant and the continuous casting apparatus. Thus, interruptions and disruptions in the continuous casting step lead to retroactive effects in the steel-making plant.

However, the demand for molten steel caused by providing melts of increased size and by providing a large number of casting channels may mean that the continuous casting capacity which is available is greater than the output of semi-finished steel to the continuous casting apparatus for billet formation. This will lead to a deterioration in the degree of efficiency.

In addition, between two melts or, when using sequential casting between two sequences, as a result of the need to empty the continuous casting installation and/or replace the worn intermediate vessels, additional operational steps are needed which lead to interruptions in production.

We have sought to provide a process and a continuous casting apparatus by which it is possible for large steel melts which are formed at time intervals which are independent of the casting cycle, to be cast in a fully continuous manner, using as far as possible, fewer casting channels than in known plants. The number of channels being dependent only on the requirements of the sequentially connected processing stages, the casting process as a whole being maintained over several melts, despite disruptions, repairs and wear on the pouring heads at individual casting channels.

Accordingly in one aspect the present invention provides an apparatus for the continuous casting of steel which comprises a reservoir vessel adapted to receive molten steel, heating means to ensure that the entire contents of the vessel are maintained at the same temperature, a plurality of conveyor channels connected to the reservoir vessel, each conveyor channel having means to regulate and/or shut off the flow of molten steel and each conveyor channel being provided with a replaceable pouring head and one or more continuous casting moulds adapted to receive molten metal from the pouring head.

In a further aspect the present invention provides a process for the continuous casting of steel in a continuous casting apparatus as defined above, wherein the molten steel is conducted from the heated reservoir vessel through the conveyor channels which can be individually regulated and/or shut off and through the pouring head into one or more continuous casting moulds, the temperature of the molten steel being the same throughout the reservoir vessel and conveyor channels.

By the use of such a process, it is possible to coordinate the production of steel and of the casting of it by using a reservoir vessel for the molten steel. On the one hand, considerably improved use of the casting time of the ladle (sequential casting) is achieved and on the other hand, by heating the whole of the reservoir vessel, it is possible to achieve a constant temperature at each discharge point. Preferably, the casting channels are electromagnetic so that movement of separate channels can be switched off or stopped, so that pouring heads which are designed for quick replacement and which, from experience, are the first parts to become worn, can be replaced. A continuous length which is only briefly stopped in the chill mould serves for the renewed starting of this continuous length.

The temperature at the point at which the molten steel is poured into the reservoir vessel and at the discharge point furthest therefrom is maintained at the same level by heating the reservoir vessel. The maintenance of a reserve of molten steel in this heated reservoir lengthens the time which can elapse between the steel leaving the ladle and entering the mould and thus corrects timing differences between the steelmaking plant and the continuous casting installation. The storage capacity of this reservoir vessel, with a delayed supply of the melt, results in a shortening of the ladle-casting time as compared with the casting time of the apparatus. With shortening of the maximum ladle-casting time, this represents the lengthening of the possible casting time of the melt.

The use of electromagnetic conveyor channels replaces stopper-guiding and stoppers enables the supply of steel to the chill mould to be so interrupted that the part which has become worn, e.g. the pouring head, can be replaced during running conditions. Individual conveyor channels which can have their supply of molten steel shut on and off enable the movement of the continuous lengths of cast steel to be stopped and started again without having any influence on the casting operation in respect of the other lengths of cast steel.

The labour requirements are reduced by the process according to the invention, since such a process renders control of the casting channels unnecessary.

The use of casting channels of the electromagnetic conveyor type makes it possible during movement of the molten steel, to separate the slag from the steel and because of the absence of ferrostatic pressure through the casting channel, leads to small penetration depth of the casting stream into the continuous casting.

The pouring head, which is fixed on the casting channel so that it can be quickly released, can be replaced when worn without waiting for the end of the melting operation or the end of the sequence. Only a small labour force is necessary for this purpose, and this also applies to the adaptation or preparation of the casting channels themselves.

The quantity of the melt in the heatable reservoir vessel, which, like the casting channel is covered, permits a rising of the non-metallic inclusions, so that the quality of the continuous casting is improved.

Further variations in the quality of the continuous casting are produced by suitable metallurgical treatment of the liquid steel in the reservoir vessel, for example, by alloying or desulphurisation, the treatment taking place according to the throughput quantity. If the reservoir vessel and the casting channel are closed off from the surrounding atmosphere by means of a cover and inert gases are introduced, any oxidation of the melt is prevented.

The supply of steel may be fed from the heatable reservoir vessel to the chill moulds via the casting channels by gravity or by the ferrostatic pressure in the reservoir vessel. In such cases, the steel may be conducted in unmeasured quantities through refractory pipes or ducts interchangeably connected to the bottom of the reservoir vessel, which pipes or ducts can be shut off near their outlet end by a slidevalve closure arrangement and may be equipped with connection means for a quick-change pouring head. A quickchange pouring head with a metering device, for example a stoppertype closure means, enables the quantity of steel supplied to the chill mould to be regulated independently of the ferrostatic pressure obtaining in the system.

The process according to the invention can be advantageously employed with single or multiple continuous casting moulds.

An embodiment using a multiple continuous casting mould in accordance with the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which: Fig. 1 is a side view of the installation in section.

Fig. 2 is a plan view of Fig. 1 with covers removed.

Fig. 3 shows, on an enlarged scale, a quick-change pouring head arranged on a conveyor channel, and Fig. 4 shows a mechanical closure means for the melt.

The multiple continuous casting installation illustrated in Fig. 1 and 2 comprises a reservoir vessel 1 with a closure cover 3 and provided with inductor heaters 2 and connected to electromagnetic conveying channels 4 with covers 5. Each channel 4 is provided with a quick-change pouring head 6 which is releasably arranged thereon. The individually adjustable inductor heaters are releasably connected to the reservoir vessel 1.

Illustrated in Figure 2 is an arrangement having six casting channels, from which it can be appreciated that it becomes possible by the arrangement of the inductor heaters 2 to obtain uniform heating of the melt which is introduced through a siphon 16 into the reservoir vessel 1. The conveyor channels 4 are detachably connected to the reservoir vessel 1.

The quick-change pouring head 6 which is illustrated in Figure 3, has a connecting means 10 comprising a guide means 7 and a sealing means 8 which permits rapid replacement of the pouring head 6. The guide means 7 and the sealing arrangement 8 may lie horizontally or vertically.

The quick-change pouring head 6 consists of a trough-shaped body 9, which has a connecting means 10 on its supply side and an opening 11 for pouring tube 12 at the discharge end. Furthermore, it is equipped with a cover 13, which is provided with a working aperture 14 which can be shut off and which is opposite the outlet opening 11.

A mechanical means for shutting off the melt for a gravity flow arrangement, i.e.

without an electromagnetic conveyor, is illustrated in Figure 4 and comprises a slide-valve closure 15, known per se, for shutting off the melt when changing over the quick-change pouring head 6. The operational procedure is therefore as follows.

The steel flows from a casting ladle through an externally arranged replaceable "siphon pouring" inlet 16 into the heatable reservoir vessel 1 and, from the latter, optionally after a metallurgical treatment, by way of electromagnetic conveying channels 4 separately to each replaceable pouring head 6.

The heatable reservoir vessel 1 is shown as an induction channel furnace of elongated form, which is disposed parallel to a series of chill moulds and which, being of this type, is provided with inductor heaters which are adjustable independently of one another, so that the steel which flows therethrough and is temporarily stored therein can be raised to a temperature which is the same over the entire furnace length. In this way, it is ensured that the temperature of the steel is the same at all casting channels and the restriction as regards the number of channels, based on the temperature difference between the pouring position and the most remote chill mould, is obviated.

A "working" aperture in the cover of the pouring head permits the flow to be observed, so that the state of wear of the head can be supervised. In order to be able to replace this part which is subject to wear, the supply of steel to this casting channel is, for example, interrupted by means of the electromagnetic conveyor channel and the quick-change pouring head, of which the point of connection with the conveyor channel is advantageously disposed outside the chill mould region, is replaced by another casting head which has already been made ready. For this purpose, the pouring head, when it is fitted with a submersible pouring tube, is lifted, for example, by means of a lifting tool, from the guide means 7 after actuating a quickrelease device, and a freshly supplied head is introduced from above into the guide means 7, whereas when pouring tubes which are not submersible are employed, the changeover can also be carried out from the side or from the front by means of suitable lifting tools or gear, as for example suitably equipped fork-lift trucks.

This replacement is advantageously so carried out, separately for each pouring head, that either the casting operation can be continued immediately after the replacement or after the removal of the worn pouring head, the casting channel is run until empty and is re-serviced before the continuous casting is once again continued with another pouring head. Independently of these measures, the casting process can be continued at the other casting channels.

Consequently, it is possible to regularly replace any one casting zone which has been subject to particular wear and to fully and continuously cast and treat steel instead of casting sequentially. The repair of the complete, stopped casting channel can also be carried out. By contrast herewith, using the hitherto known installations, the failure of one or more channels would lead to permanent reduction in the output capacity of the installations and to a premature termination of the sequence.

The heat motion generated by inductor heaters may be used for treating the steel which is flowing through the reservoir vessel. The motion assists a rapid homogenisation of the composition of the steel and its temperature. The supply of steel taking place in measured quantities individually to each casting channel also permits metallurgical treatment in the channel for each continuous casting.

As is apparent from the method of procedure as previously set forth, it is possible by using a process and apparatus in accordance with the invention, to enlarge the range of application for the continuous casting, which with known processes and apparatus was restricted by size of the melt and cross-section of the casting.

WHAT WE CLAIM IS:- 1. An apparatus for the continuous casting of steel which comprises a reservoir vessel adapted to receive molten steel, heating means to ensure that the entire contents of the vessel are maintained at the same temperature, a plurality of conveyor channels connected to the reservoir vessel, each conveyor channel having means to regulate and/or shut off the flow of molten steel and each conveyor channel being provided with a replaceable pouring head, and one or more continuous casting moulds adapted to receive molten metal from the pouring head.

2. An apparatus as claimed in Claim 1, wherein the conveyor channels are electromagnetic conveyor channels.

3. An apparatus as claimed in Claim 1 or 2, wherein the heating means comprises channel inductor heaters.

4. An apparatus as claimed in any one of Claims 1 to 3, wherein each pouring head, comprises a trough-shaped body which has connecting means on its supply side whereby it can be connected to the conveyor channel and a pouring tube on its outlet or discharge end.

5. An apparatus as claimed in Claim 4, wherein each pouring head is provided with a cover having a working aperture which can be closed off and which faces the pouring tube.

6. An apparatus as claimed in any one of Claims 1 to 5, wherein the connecting means is formed in the manner of a sliding closure device.

7. An apparatus as claimed in any one of Claims 1 to 6, wherein the pouring tube is formed as a submersible pouring tube.

8. An apparatus as claimed in any one of Claims 4, 5 or 7, wherein the connecting means is an aligning and sealing connecting means.

9. An apparatus as claimed in any one of Claims 1 to 8, wherein the heatable reservoir vessel is provided with releasable connections for an externally disposed siphon pouring device, for the heating means and for the conveyor channels.

10. An apparatus as claimed in any one of Claims 3 to 9, wherein the channel inductor heaters are distributed asymmetrically over the length of the reservoir vessel and have current control means independent of one another.

11. An apparatus for the continuous casting of steel substantially as hereinbefore described with reference to the accompanying drawings.

12. A process for the continuous casting of steel in a continuous casting apparatus as claimed in any of Claims 1 to 11, wherein the molten steel is conducted from the heated reservoir vessel through the conveyor channels which can be individually regulated and/or shut off and through the replaceable pouring head into one or more continuous casting moulds, the temperature of the molten steel being the same throughout the reservoir vessel and conveyor channels.

13. A process as claimed in Claim 12, wherein the heat is produced by electric induction and is so regulated, depending on the distance from the pouring position of the material to be cast, that the tempera- ture of each separately discharged stream of the steel from each conveyor channel is substantially the same.

14. A process as claimed in Claim 12 or 13, wherein the reservoir vessel can hold more than three times the total quantity of molten steel discharged per minute.

15. A process as claimed in any one of Claims 12 to 14, wherein the molten steel is subjected to metallurgical treatment whilst it is in the reservoir vessel.

16. A process as claimed in any one of Claims 12 to 15, wherein the flow of molten steel from the reservoir vessel through the conveyor channels to the casting heads is effected electromagnetically against the force of gravity.

17. A process for the continuous casting of steel substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. metallurgical treatment in the channel for each continuous casting. As is apparent from the method of procedure as previously set forth, it is possible by using a process and apparatus in accordance with the invention, to enlarge the range of application for the continuous casting, which with known processes and apparatus was restricted by size of the melt and cross-section of the casting. WHAT WE CLAIM IS:-

1. An apparatus for the continuous casting of steel which comprises a reservoir vessel adapted to receive molten steel, heating means to ensure that the entire contents of the vessel are maintained at the same temperature, a plurality of conveyor channels connected to the reservoir vessel, each conveyor channel having means to regulate and/or shut off the flow of molten steel and each conveyor channel being provided with a replaceable pouring head, and one or more continuous casting moulds adapted to receive molten metal from the pouring head.