EP0704664B1 - Furnace for reheating, holding and storing of metallurgical products - Google Patents

Description

The present invention relates to a reheating, holding, and accumulating products steelworks. Flat and long products treated in hot rolling mills to form sheets, strips, beams, bars, etc ... are more and more frequently made from steel liquid contained in a pocket and continuously poured into a mold followed by rollers which make it possible to extract the shape obtained by controlled cooling of steel just enough to change from liquid metal to the solid form, the semi-product thus obtained at output continuous casting is usually at a temperature higher than 1000 ° C. Given the high temperature of the semi-finished product, its rolling as soon as it leaves the casting represents a substantial energy saving by compared to the classic process which consists in storing semi finished products before heating them up 1250 ° C to be able to laminate them.

• La première est due à la non homogénéité en température des produits semi finis en sortie de la coulée en continu du fait du refroidissement préférentiel des angles et des rives des produits, ce qui rend nécessaire un complément de réchauffage et d'homogénéisation des semi produits avant laminage.
• La seconde, encore plus contraignante, vient des arrêts programmés et surtout non programmés du laminoir en cours de production pour changer un cylindre ou apporter des corrections aux différents réglages. Pendant ces arrêts, l'acier liquide présent dans les poches doit être impérativement coulé sous forme de semi produits sans pouvoir être immédiatement laminés; il faut donc pouvoir les stocker à chaud pendant des durées allant de quelques minutes à parfois une heure ou plus.
• La troisième, enfin, est d'ordre économique car les équipements de coulée en continu sont également soumis à des aléas de maintenance et de production et connaissent des périodes d'arrêts plus ou moins longues qui ne coïncident pas forcément avec celles du laminoir. Pour une meilleure rentabilité des usines, le laminoir doit dans de tels cas être alimenté à partir de semi produits non issus directement de la coulée et qui, par conséquent, doivent être réchauffés à partir de la température ambiante.

In many factories comprising a steelworks and a hot rolling mill, means are used to carry out the continuous casting and the hot rolling of semi-finished products without systematic passage through a cooling and storage area. However, this approach faces three main techno-economic difficulties:

• The first is due to the non-uniformity in temperature of the semi-finished products at the end of the continuous casting due to the preferential cooling of the angles and the edges of the products, which makes it necessary to further reheat and homogenize the semi-products before rolling.
• The second, even more restrictive, comes from scheduled and above all unscheduled shutdowns of the rolling mill during production to change a cylinder or make corrections to the various settings. During these stops, the liquid steel present in the pockets must imperatively be cast in the form of semi-finished products without being able to be immediately rolled; it is therefore necessary to be able to store them hot for periods ranging from a few minutes to sometimes an hour or more.
• The third, finally, is economic because the continuous casting equipment is also subject to the vagaries of maintenance and production and experience more or less long periods of shutdown which do not necessarily coincide with those of the rolling mill. For a better profitability of the factories, the rolling mill must in these cases be fed from semi-finished products not directly coming from the casting and which, consequently, must be reheated from room temperature.

Many known devices can be used either as storage at pouring temperature, i.e. reheat or make products from casting; in particular the invention described by the patent EP 0 370 916 B1 describes a reheating oven, maintenance, of accumulation which comprises two groups of support rails and transport rails that can both move vertically and lie in lower planes, identical or higher than reference plane given by the rollers which allow to put in and put out the steel products and, by combining the respective plans of the beams of support and transport rails, in order to whether to move the products on each of the groups of support beams.

In the oven described by the aforementioned patent, the displacement from the oven to the oven is controlled from way to either accumulate the steel products in the first zone defined by the first group of beams of support either to make them cross this area too quickly as possible to feed the rolling mill and create an available space in the oven to store it possibly products from continuous casting if the rolling mill stops.

Furthermore, DE-C-653 956 describes a device for the continuous transport of products, in particular of sheets, in continuous ovens, on one level using two groups of mobile spars alternately taking the products and describing a rectangular movement, the arrangement being such that one of the groups of mobile side members take the product from the other group and transfer it when precise where it begins or ends the horizontal advance movement. These measures known does not differentiate the residence times of products in the area storage.

The disadvantage of the installations described in the prior art lies in the limitation transfer speed which cannot be equal to or less than the cycle time and the possible travel of the transport beams. These transport beams follow a rectangular cycle with a total duration of the order of 40 seconds or more, comprising a first ascent phase which frees the side members from support, a second phase of horizontal transport then, a third phase of deposit of the products which have thus progressed by one step on the support beams before the fourth phase of going back to the initial position; we see that during phases one, three and four the products do not move, so only the quarter of the cycle is active in terms of product progression inside the oven and otherwise the step or translation in the horizontal plane of the transport beams is limited to generally less than 0.6 m due to the combination necessary vertical and horizontal movements of the mechanical.

This limitation can constitute a serious handicap as long as in terms of the furnace's production capacity than its ability to free up sufficient space in the oven to store products from casting if the stop was longer than expected or longer than usual. Furthermore, the slow speed of product transfer through the storage area, speed which represents an advantage when the products in the oven are practically cold, is a disadvantage when the semi products arrive directly from the continuous casting because it forces this area to be kept at a temperature high to avoid cooling of the products before their entry into the heating zone. This high maintenance temperature is a handicap both in terms of energy only for the environment because in normal times the products from continuous casting must come out the most quickly possible in reheating zone or even homogenization and consequently the area of storage is empty.

The present invention proposes to overcome these disadvantages in providing a satisfactory answer while both of the transfer speed problem of products and that of high temperature maintenance of the storage area by taking advantage of the fourth phase of turning back the side members of transport to advance the products in the oven as will be seen in the device which follows. To the possibility of reheating cold products that of being able, during operation, to adapt the residence time of semi-finished products depending on their temperature in the oven.

To this end, the invention relates to a storage, reheating and maintenance oven for steel products including a storage area, a heating area and a holding zone, provided with side members connecting, in the transverse direction, a charging zone and charging zone, the heating and cooling zones support comprising fixed product support beams and beams transport placed at a certain distance from said fixed support rails, said transport beams being driven in a translational movement horizontal and a lifting movement relative to the side rails of fixed support, characterized in that said storage area includes support beams independent of the oven bottom and moved in a alternative horizontal travel and mobile transport rails, same type as the transport beams of the reheating and holding.

• la figure 1 est une vue en coupe en élévation frontale, d'un four selon l'invention, illustrant la phase d'avancement du groupe de longerons de support, supportant le produit sidérurgique ;
• la figure 2 est une vue en coupe en élévation frontale, d'un four selon l'invention illustrant le mouvement du groupe de longerons mobiles en-dessous le groupe de longerons de support ;
• la figure 3 est une vue en coupe en élévation frontale, d'un four selon l'invention, illustrant le transfert de la charge du groupe de longerons de support vers le groupe de longerons de transport ;
• la figure 4 est une vue en coupe en élévation frontale, d'un four selon l'invention, illustrant le mouvement du groupe de longerons de support sous le groupe de longerons de transport ;
• la figure 5 est une vue en coupe en élévation frontale, d'un four selon l'invention, illustrant le transfert de la charge du groupe de longerons de transport vers le groupe de longerons de support, délimitant ainsi un cycle entier des mouvements du groupe de longerons de support et de transport.

The characteristics and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment thereof devoid of any limiting character. On the figs:

• Figure 1 is a sectional front elevational view of a furnace according to the invention, illustrating the advancement phase of the group of support beams, supporting the steel product;
• Figure 2 is a sectional front elevational view of an oven according to the invention illustrating the movement of the group of movable beams below the group of support beams;
• Figure 3 is a front elevational sectional view of an oven according to the invention, illustrating the transfer of the load from the group of support beams to the group of transport beams;
• Figure 4 is a sectional front elevational view of an oven according to the invention, illustrating the movement of the group of support beams under the group of transport beams;
• FIG. 5 is a sectional view in front elevation of an oven according to the invention, illustrating the transfer of the load from the group of transport beams to the group of support beams, thus delimiting an entire cycle of the movements of the group support and transport beams.

According to a preferred embodiment, the oven object of the present invention has two or more areas of storage, reheating and maintenance. In this mode of non-limiting embodiment, the oven has a so-called zone storage which should normally remain available to receive the casting products in the event of the rolling mill, a heating zone, and a zone homogenization before charging. The areas of reheating and homogenization are designed as the conventional reheating ovens with side members 2 so-called mobile or support beams 1 so-called fixed, the four-phase cycle described in the art front allows the mobile side members 2 to transport of one step per cycle the products of the entry of the zone from reheating to reheating at speeds generally varying from 0.9 m / min to 0.3 m / min or less.

The storage area includes transport beams 2 integral with a structure 4 as produced in the reheating and homogenization zones and one or two support beam groups 1 which, unlike of a usual oven, are not integral with the sole 3 fixed from the oven or as described in the patent previously cited.

The oven object of the invention has a structure 5 comprising a plurality of support beams 1, independent of the bottom 3 of the oven and capable of horizontal forward movement or the back. These groups of support beams 1 submitted only at a horizontal translation can have a stroke of 1m or more depending on the power requirements of the oven, this horizontal movement takes place with the load during phase four of the return of the beams of transport 2, which allows products to be moved from no support beams 1 linked to the structure 5 by example 1 m, this step being added to that of for example 0.6 m carried out thanks to phase two of the beams of transport 2 linked to structure 4.

• 0,6 m (pas des longerons de transport 2) + 1 m (pas des longerons de support 1) = 1,6 m pendant le temps de cycle normal de 40 secondes soit un pas de 2,66 fois plus long que celui obtenu avec les combinaisons habituelles de longerons de transport 2 et de support 1.

This combination of movements during a single cycle of the transport beams makes it possible to obtain a total displacement of: (the displacement and time values are given for information):

• 0.6 m (step of the transport beams 2) + 1 m (step of the support beams 1) = 1.6 m during the normal cycle time of 40 seconds, a step of 2.66 times longer than that obtained with the usual combinations of transport rails 2 and support 1.

Transport speed through the storage area is thus multiplied at least by 2.66 in this example reducing the residence time in the same proportion, under these conditions it becomes useless to maintain at high temperature storage area in production normal, we can be satisfied with its maintenance in temperature by the fumes from the zones of reheating and homogenization going to the conduits leading to the product evacuation chimney combustion of the oven.

In order to illustrate the operation of the oven object of the invention, we give below a chronology of different phases of the cycle:

In FIG. 1, the product P has been loaded by a means usual in reheating ovens at the entrance of the oven on the group of support beams 1 which is in position rear relative to the fixed support rails 6 of following zones, the group of support beams 1 is moves forward a full step A (in Example 1 m) during (figure 2) the mobile transport beams 2 move in opposite directions under the load P, from the value of a step B (in the example 0.6 m). In figure 3, transport beams 2 move vertically upwards by freeing the groups of spars from support 1 of their product load P which rests now on the longitudinal members 2 which advance by a step B (0.6 m) while (Figure 4) the spar groups support 1 take a step back A (1 m) to return to their initial position. Transport beams 2 arrived at the horizontal end of travel will move vertically downwards, resting the load P on the support rails 1 (Figure 5). the charge P therefore has increased forward by the cumulative value of steps A (figure 1) and B (figure 3) during a rectangular cycle complete with transport beams 2.

This progression cumulating the steps A + B continues until the product P reaches the next zone that is to say the groups of beams of support 6 which are fixed. From the moment the product P is on the groups of support beams 6 it is transported to the racking by the cycle normal rectangular transport beams 7, so at a speed corresponding to the single step 7 which is usually equal to the pitch of the first group of beams transport 2 (in the example 0.6 m).

The speed of movement of products in the storage allows it to be empty in normal times, if the rolling mill stops, the group system support beams 1 remain in a fixed position, the products are transported from the oven to the not the transport beams 2, the progression is one step B in each cycle, depending of the production required the cycles are linked (all 40 s in the example) to free a space at charging for a product coming from the casting continuously, or are separated by a downtime which can be several minutes giving speeds of displacement of the order of 0.3 m / min or less.

In the case of warm or even cold products, the time spent in the storage area must be set profit to preheat the product before its arrival in reheating zone, the speed of movement of products must therefore be modulated what we will get in increasing downtime between two successive cycles and by varying the step A from 0 m to the maximum step A (1 m in the example) as well as the pitch of the side members transport from 0 m to B (0.6 in the example). The combination of these variations in the storage area independently movement of products in the reheating zone allows to vary the time taken by the product to cross the storage area since minimum time in combining the successions of cycles and the maximum steps at infinity if the steps are zero, that is to say that the products remain on site and are regularly lifted by the transport beams 2 then re-deposited at the same location on the groups of support beams 1.

Of course, the present invention is not not limited to the embodiments described and shown above, but that it includes all variants. So, in the usual cases of casting feeds to a hot rolling mill through a storage and heating furnace, homogenization, seems sufficient to equip only one zone with groups of support beams with translational movement horizontal, it can perfectly be conceivable, for flexibility or feeding reasons since multiple flows for example, that two or all furnace areas may have such groups of support rails. We can also take into account operating conditions which make necessary the product return easily obtained by reversing the previously described order of movements and in using the horizontal return cycle of the beams of support on which the products resting while the transport beams, in the low position, progress forward.

Claims (2)

1. Furnace for the storage, heating and holding of iron and steel products comprising a storage area, a heating area and a holding area, equipped with longitudinal members linking, in the transverse direction, a loading area and an unloading area, the heating and holding areas comprising fixed longitudinal members (6) for supporting the products and transportation longitudinal members (7) placed at a certain distance from said fixed support longitudinal members, the transportation longitudinal members effecting a horizontal translatory movement and a lifting movement with respect to the fixed support longitudinal members, characterized in that said storage area has support longitudinal members (1) independent of the furnace hearth (3) and effecting an alternating, horizontal translatory movement and mobile transportation longitudinal members (2) of the same type as the transportation longitudinal members of the heating and holding areas.
2. Furnace for the storage, heating and holding of iron and steel products according to claim 1, characterized in that it comprises means for modulating the passage speed of products into the storage area, between a zero speed in the absence of a horizontal translation of the support (1) and transportation (2) longitudinal members and a maximum speed corresponding to the combination of each of the speeds of each group of support (1) and transportation (2) longitudinal members.

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