GB2202475A

GB2202475A - Continuously casting thin slab

Info

Publication number: GB2202475A
Application number: GB08706530A
Authority: GB
Inventors: Fulvio Fasano
Original assignee: Danieli and C Officine Meccaniche SpA
Current assignee: Danieli and C Officine Meccaniche SpA
Priority date: 1987-03-19
Filing date: 1987-03-19
Publication date: 1988-09-28
Also published as: FR2612098B3; GB8706530D0; FR2612098A1; DE3708685A1

Abstract

The continuous casting system includes a tundish (11) with a pouring device (20 or 120) for conveying molten metal from the tundish (11) to an ingot mould (12) with its inlet aperture (112) below the tundish (11). The device (20 or 120) has one or more suitable slender discharge openings to produce a thin cast slab. The slab may be directly hot-rolled and coiled. In an embodiment, the detailed structure of discharge nozzle is described (Figs. 4 and 5, not shown). <IMAGE>

Description

Continuous Casting Svstem To Obtain Thin Slabs.

This invention concerns a continuous casting system to obtain relatively thin slabs. To be more exact, the invention concerns a continuous casting system able to produce thin slabs of which the thickness is substantially much smaller than their width.

The invention can be employed in all those cases where it is desired to obtain a cast slab which is wide and relatively thin for the subsequent production, for instance, of strip by hot rolling.

The invention lends itself to the rolling of strip from relatively thin slabs directly in line with the casting process without intermediate passes.

Various attempts are known in the prior art which are intended to obtain thin slabs, or even strip directly to undergo subsequent finishing passes.

Among the known systems tried are continuous casting machines which employ tracks, machines with belt and casting wheel, machines with forming drum or forming rollers, etc.

All the known continuous casting machines entail problems which have not been overcome hitherto, and industrially satisfactory embodiments have still not been produced.

In fact, the known embodiments are generally complicated and, owing to their particular operating methods (active entraining of the molten metal by rotary or sliding devices), cannot produce a satisfactory product quality. Moreover, the known embodiments are not reliable enough for application industrially.

A purpose of this invention is to overcome or minimise the drawbacks inherent in the known embodiments by providing a particularly reliable and industrially applicable continuous casting system for relatively thin slabs.

A first purpose of the invention is to make possible a continuous casting system which results in a relatively thin slab by employing a plant comprising the traditional components (ladle, tundish, ingot mould, roller guide, drawing equipment), such components having been specially adapted and correlated to produce such relatively thin slab.

By relatively thin slab there is visualized a slab having a slender thickness as compared to its width, the ratio between thickness and width preferably ranging from 1:10 to 1:100.

Another purpose of the invention is to make possible a slab to be produced which is suitable to be rolled thereafter in-line to obtain strip, perhaps after a pass through a pre-heating or temperaure-equalisation furnace which is also positioned in-line.

The invention overcomes the problem of the employment of an ingot mould having a relatively slender, elongate rectangular section corresponding to the slab to be produced.

It is well known that continuous casting machines comprising an ingot mould fed from a tundish entail the necessity of aligning the casting of molten metal into the ingot mould. This problem is particularly evident in the initial casting step when the casting has still not stabilized.

Such problems of controlling the casting, which are already appreciable with traditional ingot moulds having a square or rectangular and slightly elongate section, become very severe when it it is desired to employ ingot moulds having a relatively thin and elongate section.

The invention arranges for a minimum possible distance between the supplying tundish and the ingot mould to be feasible. It also provides for the use of a pouring device located in the lower side of the tundish and able to obtain a casting of molten metal or several castings of molten metal which are slender enough to fall within the small aperture of the ingot moulds without leading to undesirable overflowing of molten metal.

The discharge opening of the or each pourer may reach the immediate neighbourhood of the inlet aperture of the ingot mould or possibly may be within the ingot mould itself.

According to this invention there is provided a continuous casting system to obtain relatively thin cast slabs which includes a tundish provided with a pouring device for conveying molten metal from the tundish to an ingot mould with its inlet aperture below the tundish, the said pouring device having at least one suitable slender discharge opening to produce a corresponding relatively thin cast slab and the said discharge opening(s) being located in the immediate neighbourhood of the inlet aperture of the ingot mould or within the ingot mould.

A first embodiment provides for the employment of a pouring device comprising individual pourers which each have a discharge opening; in this way the flow of molten metal from the tundish to the ingot mould is split into a series of slender castings which may have a substantially circular, rectangular or elliptic section.

The individual pourers may be arranged spaced apart from one another in a row.

Another embodiment provides for the use of a single pourer having a relatively thin elongate shape.

It may have a discharge opening in the form of an elongate slit with a section smaller than the inlet aperture of the ingot mould. In this way a single slender and elongate laminar casting can be obtained.

The pourer or each pourer of the said pouring device may comprise an inner channel having a section that becomes progressively narrower towards the said discharge opening, for example, becoming reduced from a circular section to an oval, rectangular or elliptic section. Another possibility is for the pourer or each pourer of the said pouring device to comprise an inner channel having a substantially constant section with or without terminal narrowing and a terminal insert having an opening constituting said slender discharge opening.

The said terminal insert will be provided where there is no terminal narrowing of the inner channel.

Control of the level of molten metal in the ingot mould may be obtained in any manner now in use.

Control of the pouring device may be obtained with axial plugs or slide valves or other systems now in use, one single shut-off device being provided for all the pourers where more than one pourer is provided, or else one shut-off device being provided for each pourer.

In any event the invention can also be applied where the or each pourer is free and not restricted by a control of its opening and closure.

There will now be described a set of preferred embodiments of the invention by way of example with reference to the accompanying drawings, in which: Figure 1 gives a diagrammatic view of a possible continuous casting system according to the invention; Figure 2 shows a first embodiment of the invention with several pourers; Figure 3 shows an embodiment with one single elongate pourer; Figure 4a shows a lengthwise section of a pourer; Figures 4b and 4c are sections along A-A and B-B of Figure 4a respectively; Figure 5a is a lengthwise section of another type of pourer; Figure 5b is a plan view of the wider end of such pourer; Figure Sc is a plan view of a wear insert at the narrow end of the pourer of Figure 5a.

Figure 1 shows a continuous casting system 10 comprising a tundish 11 located immediately above an ingot mould 12.

The ingot mould 12 has a relatively thin section of its inner rectangular channel, such section corresponding to the section of the slab to be produced.

Immediately downstream of the ingot mould 12 is located a secondary portion of the casting system, consisting of a curved roller conveyor 13 with a drawing unit 14.

In the system of Figure 1 a cast slab 18 is made to pass through a heating furnace 15 for immediate onward transmission to a rolling mill, shown diagrammatically at 16, for the production of strip 19.

Such strip is then cooled and coiled at a conventional coiling station 17.

The operations of producing the cast slab 18, heating it in a furnace 15, rolling it in the mill 16 and coiling the strip 19 thus produced take place inline in the example shown. The finished strip product may thus be produced directly in-line, starting from a casting bath.

The invention enables the distance between the tundish 11 and ingot mould 12 to be as short as possible so as to allow the molten metal to be poured correctly into the ingot mould, that is to say, it is desired that the end of the pourer should be positioned in the immediate neighbourhood of, or even within, the inlet aperture of the ingot mould 12.

Figure 2 shows a possible embodiment to obtain a casting wherein the molten metal from the tundish has to be introduced appropriately within inlet aperture 112 of the ingot mould 12. In this embodiment the tundish 11 is equipped on its lower side with a pouring device comprising a plurality of pourers 20, each of which is shaped like a funnel.

In this way the casting of molten metal is split into a number of castings equal to the number of pourers. This enables the section of the castings to be kept at a value such as will make it possible to align the castings with the inlet aperture 112 of the ingot mould 12 without any losses of molten metal.

Figure 3 shows an alternative embodiment in which there is one single pourer 120 that has a thin, elongate shape like that of the inlet aperture 112 of the ingot mould 12. In this way there will be a very thin laminar casting which will remain within such inlet aperture 112.

Of course, the pourers 20/120 shown in Figures 2 and 3 respectively are only indicational since their number and their outlet section may vary to suit the specific requirements and the section of the slab to be produced and to suit also the flow of molten metal to be maintained.

Figure 4a shows an example of an especially suitable pourer. The pourer 20 shown comprises an upper portion 21 for attachment to the tundish 11.

The pourer 20 has substantially the shape of a funnel, with a channel 22 which initially has a circular section, but its lower section becomes narrower until it ends with a substantially rectangular terminal outlet 23.

Figures 4b and 4c show two cross-sections along A A and B-B respectively of Figure 4a. Such crosssections make clear the development of the channel 22 with a progressively variable section.

Figure 5 shows a lenthwise section of an alternative embodiment of a pourer 220, which comprises an inner channel 122 of a substantially constant section, which is circular in this instance. At the lower end of the channel is located a wear insert 24, within which is machined an outlet hole 23 having a reduced section as compared to that of the channel 122 with the circular section. In this example the section of the outlet hole 23 is shaped like a slot with rounded ends but could have a rectangular or elliptic section or a section of another form suitable for the purpose.

The wear insert 24 will preferably be exchangeable.

In variants which are not shown here a pouring device can be provided with two or more terminal casting outlets, for instance with two or more nozzles possibly tilted at an angle to each other.

The concepts and embodiments of this invention can be applied also to a continuous casting system having a sloped or almost horizontal development instead of to a vertical ingot mould 12 as shown in Figure 1.

All these variants remain within the scope of this invention.

Claims

1. A continuous casting system to obtain relatively thin cast slabs which includes a tundish provided with a pouring device for conveying molten metal from the tundish to an ingot mould with its inlet aperture below the tundish, the said pouring device having at least one suitable slender discharge opening to produce a corresponding relatively thin cast slab and the said discharge opening(s) being located in the immediate neighbourhood of the inlet aperture of the ingot mould or within the ingot mould.

2. A continuous casting system which is adapted to produce relatively thin cast slabs in which the ratio between the thickness of the slab to its width ranges from 1: 10 to 1:100.

3. A continuous casting system as claimed in Claim 1 or Claim 2, wherein the said pouring device comprises individual pourers which each have a discharge opening.

4. A continuous casting system as claimed in Claim 3, wherein the individual pourers are arranged spaced apart from one another in a row.

5. A continuous casting system as claimed in Claim 1 or Claim 2, wherein the said pouring device consists of a single pourer having a relatively thin elongate shape.

6. A continuous casting system as claimed in any preceding claim, wherein the pourer or each pourer of the said pouring device comprises an inner channel having a section that becomes progressively narrower towards the said discharge opening.

7. A continuous casting system as claimed in any one of Claims 1 to 5, wherein the pourer or each pourer of the said pouring device comprises an inner channel having a substantially constant section with or without terminal narrowing and a terminal insert having an opening constituting said slender discharge opening, at least where there is no terminal narrowing of the inner channel.

8. A continuous casting system as claimed in any preceding claim, which includes downstream of the ingot mould guide roller means to guide the cast slab and optionally drawing means to draw the guided cast slab.

9. A continuous casting system to obtain relatively thin cast slabs substantially as herein described with reference to Figure 1 and Figure 2; or Figure 1 and Figure 3; or Figure 1 and Figures 4a,4b and 4c; or Figure 1 and Figures 5a,5b and 5e of the accompanying drawings.