The present invention relates to an interconnect¬ ing unit between at least one manufacturing line of hot steel flat products, such as thin slabs or strips, and only one finishing rolling line to strip or the like, downstream.

It is known that along the hot manufacturing line of steel flat products, in particular thin slabs and strips, it has been proposed to use devices for the temporary coiling of the product, before its finish¬ ing, in order to separate the low speed section (long winding times), connected with the continuous casting, from the finishing rolling section downstream, which occurs at high speeds (short times of uncoiling), thus forming coils to be used as feed stocks, possibly movable along the production line to the most suitable position from which the product can continue its processing on line, upon uncoiling.

A device ot this type is the so-called "Coil Box" which is commonly used for hot rolling plants of conventional type, where the coiling time, upon rough¬ ing, is comparable with that of uncoiling for finish- ing rolling . In those c ases wherein the winding time is long, such as when the roughing step is directly connected with casting, the Coil Box shows on the contrary a series of inconveniences. The Coil Box, as developed by Stelco (Canada), substantially comprises a number of inlet rollers for bending the flat

product and preparing the same to winding, as well as motorized rollers for imparting the necessary rotation to the product itself in order to cause the formation of a coil, which occurs freely, without a central c core for winding and without box housing. This method of intermediate temporary coiling, as well as the relevant apparatus, shows some drawbacks, the first of which is that of being unsuitable for too slight thickness values, e.g. lower than 25/30 mm, otherwise 0 the coil is actually collapsed while assuming a flattened shape, also depending on the speed at which the product is fed forward. Thereby, if between the parameters thickness and velocity there is not provi¬ ded a perfect calibration, taking also into account 5 the temperature, the coil thus obtained takes ovalized shapes whose deformation becomes even greater during transportation for the necessary movements on the line, as the transportation is carried out such as by previously inserting a cylindrical core in the empty 0 central portion of the coil itself. The objective, remarkable difficulty of coil boxing, even more criti¬ cal owing also to this particular type of transporta¬ tion, especially when a long time of coiling is involv¬ ed, gives then rise to problems of oxidation, as well 5 as of fast cooling, whereby it is necessary to re-heat the coil in a batch-type furnace, such as rotary furnace or the like, before the subsequent process¬ ing.

It is true that more recently an attempt has

• _j O been made to obviate these inconveniences by providing the above-mentioned intermediate coiling in a number

of stations, so that they are alternately one in a winding step and another unwinding, all being boxed and mounted each on a tiltable structure, thus having in turn a coil at an upper position, such as in a winding step, and one at a lower position, in unwind¬ ing step or vice versa. This apparatus shows within the housing box a furnace for maintaining the coil temperature and has been manufactured e.g. by MDS (Mannesmann Group) for the steel manufacturing factory ISP of Cremona (Italy) and is commonly called "Cremona Box" or "Cremona furnace".

However, even with such a solution, the problem of production capacity cannot be solved, as it is rather a rigid solution and provides for a casting line aligned with the finishing rolling mill whereby, as a consequence of the difference between the duration of winding and unwinding steps, long waiting times of the finishing rolling mill are experienced. By adopting a plurality of casting lines which feed in parallel the finishing rolling mill, the latter, having a much higher productivity, can be prevented from remaining uselessly standstill.

However, to reach this result it is necessary to shift laterally at least some of the coils produced by the casting lines. A lateral shift cannot be carried out with the above-mentioned "Cremona Box" whereas it could be imaginable with the previous

"Coil Box". In this case however there should be the need of providing a complex system of driving and intermediate heating, while anyhow the above-mentioned drawbacks would still remain as well as the uncertaint-

- k -

ies about the result.

Apart from this important aspect bound to the productivity of the plant, two additional inconveniences shown by the above-mentioned "Cremona Box" should also to be considered, and namely the impossible access to the lower mandrel for maintenance and replacement purposes unless by completely dismantling a whole upper furnace, and the necessity of ensuring that the tail of a coil remains at the outside of the housing, upon winding, thus preventing the same from entering the "Cremona box", otherwise the subsequent step of unwinding the coil itself could result to be extremely difficult .

Therefore it is an object of the present invention to provide an interconnecting unit between feeding lines upstream and a finishing rolling line to strip, downstream, which may reduce the period of waste time in operation of the finishing rolling mill. Thus the latter may be fed from a plurality of lines in parallel, with a better productivity of the plant. Such an interconnecting unit can be advantageously used also between one feed line and a finishing line.

In any case, even if the feed line is only one, another object is that of providing a temporary intermediate winding device for coiling the cast product, without the drawbacks of the prior art , in other words to ensure a non-ovalized coil shape, as much as possi¬ ble independent on the thickness, the temperature and the winding speed, that maintains the temperature at high levels without the need of further re-heating stations, may reduce as much as possible the oxidation

of the wound product, and also will allow a good acce¬ ssibility to the winding mandrel during maintenance or replacement, and in addition will not require to keep free the tail end of the wound product at the outside of the apparatus.

An additional object is that of allowing to choose the adoption of more than two winding/unwinding stations in series for each feeding line, thus achiev¬ ing the aim of a greater capacity of storing, in case of temporary stops downstream, without therefore being compelled to stopped the production upstream, and also the possibility of increasing the time of stay ("soaking time") in the zones of temperature keeping/ re-heating, at the same time providing an installed stand-by station, without prejudice for the fact that only two stations are sufficient for the operation, alternately for each line upstream. All the above is not thinkable with the "Cremona Box" which, due to its conformation, restricts to the number of two the coiling/uncoiling units.

This objects are obtained with an interconnect¬ ing unit showing the features of claim 1.

Particular embodiments of the same unit are obtained through the features of the sub-claims. This and additional objects, advantages and characteristics of the interconnecting unit according to the present invention will be clearer from the following detailed description of a preferred embodi¬ ment thereof, given as a non-limiting example with reference to the annexed drawings in which:

Figure 1 shows a partial perspective view of a

plant for the production of hot rolled steel strips from two lines of continuous casting, in correspondence of an interconnecting unit according to the invention with downstream a line of finishing rolling; and Figure 2 shows a side view, partially in cross- section along line II-II of figure 1, i.e. along the longitudinal axis of the mandrel of a coiling-uncoiling apparatus with elongated mandrel at the winding station. With reference to the drawings, a plant for the production of steel strips from continuous casting has two feed lines 1, 1 ' feeding a hot steel flat product 10, 10' from continuous casting and roughing rolling at a low speed and, downstream of an interconnecting unit U according to the present invention, only one line 2 for feeding the same flat product 10 to a finishing rolling mill (not shown) at a high speed. It should be noted that, as will be stated again in the following, the feed lines upstream of the unit U could also be provided in a number diffe¬ rent from two, such as only one or possibly three.

The interconnecting unit U comprises, according to the present invention, for each inlet line, two or more coiling stations 3_ 3a; 3' _> 3'a for the fed mate¬ rial to keep temperature as constant as possible in the time. These stations are aligned with the respective feed line 1, 1' and in series to each other, so that the material may be wound alternately on either of said two stations in line as will be better explained in the following. At a central position within the interconnecting unit U and aligned with the outlet line 2, there is

provided a single series of unwinding stations 4, 4' , each of which is in turn aligned in a transverse direction with the respective winding stations 3 _. 3' ; 3a, 3'a with which it is respectively positioned side by side. Each unwinding station 4, 4' is provided by the stroke end position reached by a mobile portion of the appara¬ tus at the inside of the winding stations when the formed coil, designated with the reference number 20 in figure 2, shall reach such a position for unwinding and feeding the line 2.

More in particular and in other words the interconnecting unit U of the present invention is formed of a number of devices 9 _> which is determined by the number of inlet or feed lines 1, l ¹ .... multi- plyed for the number of coiling stations 3 _. 3a (and consequently of uncoiling 4, 4') provided for each line. Therefore these apparatuses are in number of four in the embodiment shown in figure 1, where two inlet lines 1, 1' and two stations of coiling/uncoiling i ⁿ series are provided. In general the number may vary from a minimum of two for a single feed line at the inlet until a maximum of nine for three inlet lines with three stations in series.

Each apparatus 9 comprises a motor unit 5 _. 5a, ecc. connected by means of an elongable arm 6, 6a with the corresponding coiling station 3 _. 3a,.... and more precisely with a mobile portion of such an appa¬ ratus, formed of the a coiling-uncoiling mandrel 7 mounted on a transferring carriage 7a to which a portion 8a (anyhow movable, capable to be possibly opened as a door or a guillotine) of the box housing

structure 8 of the apparatus is integrally fixed, e.g. as illustrated, when it is at the winding station. At the inside of housing 8 there is kept of course stationary each means provided for heating and/or maintaining the temperature and acting onto the wound coil 20 ( also visible in figure 2 within the winding station, but only by a broken line profile). The roller trains 11 (in figure 2 only one roller is shown) should be noted in the drawings, guiding the flat product 10, 10' towards the interconnecting unit U, more precisely to the respective coiling station. It will be also noted that for each one of said roller trains, there can be provided an extension 11' of the same array of rollers, even downstream of the last coiling station 3 _. 3' _ to be used in case at least a part of the material is not to be sent to the subsequent finishing rolling step along line 2, but in a simple way to the production of plates which can be cut from the same thin slab or strip arriving from the line in correspondence with a suitable station of withdrawal of plates, downstream of the interconnecting unit U.

When observing more in particular figure 2, there is seen that in the embodiment shown the elonga- ble arm 6, 6a is formed of two co-axial and telescopic shafts, in mutual engagement as they are e.g. spline broached on the contacting surfaces, the hollow one of them, having the greater diameter, being connected at an end to the outlet of a reducing gear 5a which in turn is driven by a motor 5 capable of rotating in both directions.

At the opposite side of the bearing of the

reducing gear 5a, the shaft is supported by an upright mounting 12 for limiting the shaft deflection, espe¬ cially at the completely extended position of the inner shaft 6 at the outlet of which the mandrel assembly 7 is connected being mounted on a slidable and motorized support 7a of whichever known type, and integral, in the illustrated example, with a wall portion 8' of housing 8 at the side opposite to that at which the shaft 6 enters housing 8 during its elongation. Since the mandrel assembly 7 with the coil 20 wounded thereon has to leave said housing to reach the uncoiling station 4, it shall consequently carry therewith a portion, even of reduced size, of the boxing structure or otherwise the latter will have to open in whichever else known way to let the mandrel pass. However the re-heating means (not shown) remains stationary at the inside of the housing within the winding station 3» As far as the formation of coil 20 on the mandrel 7 is concerned, this can be performed in whichever known way, but preferably the mandrel axis, that is aligned with the axis X-X of the shafts 6, 6a, may have e.g. a groove in which the leading edge of the strip-shaped material 10 is fitted to start the winding step. In addition suitable shunt- ing devices of known type are provided, also not shown, to direct the head of a thin slab/strip moving forward to either one or the other coiling station 3 and the¬ reby to the respective apparatus 9» These devices may be provided for example merely by pairs of rollers which can be oriented upon control so as to cause the material to move forward on the train of rollers

until a subsequent coiling station, or to direct the same toward an inlet slot ( also not represented) of the housing frame 8.

To better clarify the above, the operation of the interconnecting unit of the present invention is the following: the strip-like product from at least one plant of continuous casting and e.g. a subsequent roughing mill for each plant on one or more lines parallel to each other is directed, by means of the above-mentioned shunting devices, to the selected coiling station of the two or more ones provided on the line, such as not to be already occupied by a wound coil for maintaining of its temperature, or not to be in the situation of having its mandrel assembly shifted to the uncoiling station. The switch¬ ing of two successive thin slabs or strips from a station to the other occurs through an operation of the shunting device and gives rise to an almost instant operation of the switch itself. The apparatus is particularly suitable for thicknesses of less then 35 mm and temperatures between 900 and 1200°C.

Immediately the gear motor unit 5~5a controls the winding operation by causing the mandrel to rotate until completion of coil 20 still within station 3« As soon as the winding of thin slab or strip is over, the mandrel stops its rotation and the mandrel assembly 7 with the associate support mounting 7a and possibly the wall 8' (which instead can open without shifting) moves sideways while carrying the coil 20 outside of the winding station and heating chamber, until reaching the uncoiling station 4 on the line 2 for the finishing

rolling step. Also in this position the coupling of mandrel 7 with the respective drive motor 5 is ensured through the telescopic shafts 6, 6a which can thereby provide to unwinding the material upon inverting the rotating direction of the mandrel, once suitable known equipments have oriented the trailing edge of the thin slab, now become leading edge, towards the line 2 and finishing rolling mill. Therefore the latter can be subsequently fed by either of the uncoiling stations without interruptions or standstills due to the fact that said uncoiling stations 4, 4' .... are in turn fed alternately with the slabs coming from either one or the other feeding line upstream.

It should be appreciated that in every coiling station 3 _. 3' there are provided active re-heating units, such as by burners or the like. The mandrel 7 of a high temperature resistant alloy, the respective supports 7a and the extendable arms 6, 6a are cooled such as by water. In addition the mandrel 7 is insulated at the surface of contact with the innerest coil turn. As already stated above not only the coiling stations for each line ( and consequently the correspond¬ ing uncoiling stations) may be even more than two, but also the feed lines at the inlet may be more than two, but hardly more than three), provided that the mandrels relating to the most external line can have such an extension to reach in any case without interferences the line of uncoiling stations 4, 4' on the same finishing line 2. In any case the alternation of winding and unwinding step may occur following an arbitrary sequence according to the needs of the

plant, both upstream for the inlet lines, and down¬ stream for the outlet line.

Even when only one inlet line is provided, as already stated in the foregoing, there could be advan¬ tages by employing two or more winding stations to be used alternately and independently from each other, being able to move trasversely until reaching a position on the unwinding line, still in alternative, thus having anyhow a better flexibility of the plant and enjoying the above-mentioned advantages with respect of the coiling-uncoiling device adopted so far.