WO1992013109A1 - Method and apparatus for cooling and quenching flat products moving along a path - Google Patents

Abstract

The apparatus comprises a device for passing flat products (2) between two rows of adjustable-flow rate water sprayers (3, 3'; 4, 4') arranged crosswise to the direction of the products in a plurality of adjacent modules which are spread out along part of the path followed by said products. Said apparatus includes, in at least one (M1?, M2?) module placed at the start thereof, devices (11, 11'; 12, 12'; 13) for projecting a steady stream of unatomized water onto both sides of the materials with a flow rate which is determined so that, when it is added to the maximum possible flow rate of sprayed water in said module, the greatest possible exchange of heat is achieved.

Description

 Process and installation of cooling in the runway with quenching of flat products.

The present invention relates to a process and an installation for cooling in the runway, of constant direction or of alternating directions, of flat products, and, more particularly, "to such an installation equipped with means making it possible to provide an optional quenching of these products.

French patent No. 2,578,553, known in the name of the applicant, is known from a system for cooling the parade of flat products by spraying which comprises two rows of spray bars between which the plates pass and suction boxes interposed between the ramps placed above the upper faces of the plates which pass horizontally.

The spray bars used are of a particular type, described in French patent No. 2,578,449 also filed in the name of the applicant. Each boom comprises a spray head directed towards one face of the plate to be cooled, this head comprising a slot for the flow of the coolant and, on either side of this slot, other slots for the passage of '' an overpressure gas which sprays the coolant. This gives very good transverse homogeneity of the sprayed liquid. These ramps also have the advantage of allowing significant variations in the flow rate of sprayed water. Installations of the type described above have been constructed in the steel industry for cooling metal plates leaving rolling mills. In Figure 1 of the accompanying drawing is shown in phantom a typical skin temperature profile obtained with such an installation. It thus appears that it is possible to change the skin temperature of a plate from 800 ° C to 200 ° C in less than 10 seconds, which is well suited to many steel products in plates. By adjusting the flow rate of sprayed water, ^"has also with such an installation, a large heat flux adjustment range of cooling, 0.3 to 1.5 MW / m ² for example with water at 20 ° C.

For certain metallurgical products, however, the need appeared to provide such an installation with a capacity for increasing the cooling rate at the start of treatment, as shown on the speed profile marked T _skin in FIG. hatched area visualizes the offset of this profile compared to that discussed above and identified in phantom. It is then a question of abruptly lowering the skin temperature (T _pβau ) from 800 ^β C to 200 ° C for example, by a quenching operation carried out at the head of the treatment installation. Another constraint posed by metallurgists is that the means used to obtain this quenching in no way disturb the operation of the installation when it is conventionally used, without quenching. This is indeed a very large installation, with complex settings that should be kept because of the long and costly efforts that were necessary to obtain them. The present invention therefore aims to provide a cooling process implemented in an installation of the type described above and which gives it an optional and additional quenching capacity, without the operation of the installation being disturbed when this capacity is not used. The present invention also aims to achieve such an installation using only the means for adjusting the sprayed water flow rate of the installation, to adjust the cooling rate profile of a predetermined quenching. These aims of the invention are achieved, as well as others which will appear on reading this description which follows, with a process of cooling in the procession with quenching of flat products, in an installation where these products pass between two rows of adjustable spray water spraying booms arranged transversely to the product running direction, in a plurality of adjacent modules. According to the invention the two sides of the products are additionally sprinkled as they pass through at least one module located at the head of the installation, with a flow of irrigation water fixed by construction such that the sum of this fixed flow and the water flow sprayed maximum..possible in this module ensures the strongest heat exchange of quenching to be achieved in said module.

This additional watering at the top of the installation makes it possible to obtain the desired quenching. When it is cut, the installation returns to its previous operation without quenching, without disturbing this operation.

According to an advantageous characteristic of the method according to the invention, a desired quenching is established by adjusting the flow rate of water sprayed into the module where are installed additional sprinkling means in non-sprayed water.

So by adjusting by construction. the fixed flow rate of irrigation water at a value which, added to the maximum sprayed water flow rate of the module concerned, makes it possible to achieve the highest heat exchange required, it is ensured that the installation has a large area setting the quench itself.

For the implementation of this method, the invention provides an installation comprising means for passing flat products between two rows of water spraying booms with adjustable flow arranged transversely to the running direction of the products, in a plurality of adjacent modules distributed over part of the trajectory followed by the products. According to the invention, the installation comprises, in at least one of the modules placed at the head of the installation, means for watering the two faces of the products with water at a rate fixed by construction, determined so that it added to the maximum flow rate of water sprayed possible in said module, ensures the highest heat exchange of quenching to be carried out in this module.

According to a first embodiment of this installation, in which the products pass by substantially horizontally on a path defined by support and drive rollers, suction boxes being interposed between the spray bars arranged above the product path, said sprinkling means comprise at least one distribution bar d sprinkling water on the upper face of the products, installed in a suction box so as to release around this ramp a space allowing a suction of moist air by the box. According to another embodiment of an installation of the same type, the irrigation water distribution ramp on the upper face of the products is installed, rather than in a suction box, in a space formed between a ramp spraying water and a wall of a compartment containing this ramp, leaving a space allowing additional air circulation between this ramp and this wall towards the suction boxes.

According to an advantageous characteristic of the installation according to the invention, said water sprinkling means further comprises at least one water supply ramp arranged under the path of the products and equipped with a series of regularly staggered distributor tubes to water the underside of the products, these ramps being shaped as a support for means for guiding these products, between two adjacent rollers.

These crawlers thus play a double role, of supplying water on the one hand and of supports for guiding the flat products on the other hand. These supports were present in an installation not improved by the present invention. The use of these supports to bring the irrigation water to the underside of the products to be treated makes it possible not to disturb the geometry of the installation at this level and therefore to keep all the settings established in the absence of these watering means. Other characteristics and advantages ^" of the present invention will appear on reading the description which follows and on examining the appended drawing in which: FIG. 1 is a graph of the cooling rates discussed in the preamble to this description,

FIG. 2 is a diagram of a cooling installation with quenching according to the present invention,

- Figure 3 is a cross section of a preferred embodiment of a spray bar of the upper fac of the products to be treated in the installation according to the invention, - Figure 4 is a cross section of the means arranged between two rollers for supporting and driving the products to be treated, to spray water on the underside of these products and to sprinkle this side with water contained in the water supply ramps according to this invention, and

- Figure 5 is a flow diagram for adjusting the water flow in the various modules constituting the installation according to the invention, illustrating various operations of this installation. Reference is made to the diagram in FIG. 2 of the appended drawing and to the aforementioned patents to describe the structure of an installation according to the invention. This comprises support and drive rollers 1, 1 ′, 1 ", etc., arranged so as to cause a flat product 2 such as a metal plate or sheet metal coming out of it to circulate in a substantially horizontal plate. 'a rolling mill in the direction of arrow F. The plate passes into the installation so that its temperature drops according to a predetermined cooling speed profile. In Figure 1 the cooling speed profile is illustrated at 1' using the skin temperature T _skin , accessible by measurement. The average temperature T _B and the core temperature T _core of the plate have also been shown in this figure. The average temperature corresponding to the skin temperature which can be measured in a cooling installation of the type described in the aforementioned French patent No. 2,578,553, fitted out in accordance with the present invention. The skin temperature T _pβau drops suddenly to a level below the desired final temperature T _f which is of the order of 200 ° C. in the example illustrated, at the outlet of the installation, this outlet being reached - after about 10 seconds by the plate. Like the installation described in French Patent No. 2,578,553, the installation according to the invention is used to spray a coolant such as water on both sides of a plate circulating on the rollers 2. A for this purpose, the installation comprises two rows of spray bars 3, 3 ′, etc. and 4, 4 ′, etc., placed respectively above and below the circulation plane of the plate 2 to be cooled.

The upper spray bars 3, 3 'are of the type described in the aforementioned French patent No. 2,578,449 and therefore each comprise a spray head 5, 5 ", etc., where a central blade of water is sprayed by lateral air inlets, so as to fill a transverse prismatic volume resting on the upper face of the flat product 2. Inside this volume (defined in broken lines in FIG. 2), the distribution of sprayed water is very homogeneous.

As described in the aforementioned French patent No. 2,578,553, a suction box 6 separates two adjacent ramps 3, 3 '. A fan (not shown) draws moist air upwards, in the direction of the arrow G, this air coming from the area near the upper surface of the plate or sheet 2, where the air is charged with droplets protruding from the surface of this plate 2, after impact on the latter. The moist air thus collected is entrained towards drying means (not shown). Gutters 7, 7 'ensure the recovery of condensed water flowing over the walls 8, 8' of the box. These extend towards the trajectory of the plates 2 by movable skirts 9, 9 'which confine and isolate the reflective zones while allowing the passage of a possibly deformed plate or sheet, without deterioration of the boxes. All of these provisions are described more fully in the aforementioned French patents which will be referred to for more detail.

In an industrial embodiment designed for the cooling of sheets-at the exit of the rolling mill, several ramps 3, 3 ′, etc. have been brought together (for example four ramps) and the associated ventilation boxes in a removable module in which the four boxes are connected to the same suction fan. The removable nature of the module, which can be removed transversely from the installation, facilitates its maintenance. The complete installation can thus comprise five or more modules, arranged one beside the other parallel to the trajectory of the sheets defined by the rollers 2. Likewise, the ramps 4, 4 ′ etc.— placed under this trajectory, between the rollers 1, l ', 1 ", etc ... are grouped in removable modules of four ramps (for example) for the same reasons. Between the rollers, the sheets are guided by crosspieces 10, 10', etc ... constituting a support plate for the sheets. These crosspieces 10, 10 ′ are carried by pairs of transverse beams 11, 11 ′ and 12, 12 ′ respectively. Each ramp module 4, 4 ′, etc. is placed at the right of a ramp module 3, 3 ′, etc. The aim of the present invention is to incorporate into such an installation, known per se from the aforementioned patents, an initial quenching capacity suitable for obtaining 'a cooling speed profile such as that shown in phantom in Figure 1. This The initial quenching must then be carried out in the module or modules placed at the head of the installation, where the sheets penetrate into it. It is therefore at the level of these modules that water sprinkling means are installed which will now be described. Next -a. preferred embodiment of the invention, these means comprise, above the trajectory of the sheets, water distribution ramps such as the ramp 13 arranged transversely in the suction box 6. Thus the head module of the installation can include four ramps of this type installed each in one of the four boxes of the module. Such a ramp (shown in more detail in Figure 3) is constituted by a tube 14 of generally rectangular section for example, mounted by a flange 15 on one end of the box. The thickness of the tube, parallel to that of the box, is thinner than the latter so as not to block the box and to leave a passage for the humid air sucked in from the space located above the sheet 2. The ramp also clears the space between the gutters 7, 7 ′ for the same reason. Incidentally, it will be noted that spacers such as the spacer 17 maintain the spacing of the walls 8, 8 ′ of the box 6.

Distributor tubes 16 pass through the lower wall of the tube 14 of rectangular section constituting the ramp. These tubes are regularly arranged a few centimeters from each other, over the entire length of the ramp. Preferably, the upper ends of the tubes 16 are arranged below and close to the upper wall of the tube 14, as shown in FIG. 3. The tubes 16 then operate in "overflow" and it is then possible to quickly stop the feeding of the tubes 16 by cutting that of the tubes 14. In fact, the feeding of the tubes 16 ceases as soon as the level of water in the tubes 14 drops below that of the upper end of the tubes 16.

One could otherwise arrange the tube 16, for example as indicated at 16 'in FIG. 2, where a flow of water has been shown diagrammatically through the upper face of the tube 14, under the effect of an overflow and the gravity.

The flow of irrigation water falling from the tubes 16 (or

16 ') on the sheet 2, thus greatly increases the heat flux exchanged with this sheet, by adding to the flow of water sprayed by the ramps 3, 3'. In Figure 2, it appears that the ramp 13 sprinkles a range of the sheet located between two areas which receive water sprayed by the ramps 3, 3 '. Favorably, the water thus discharged by the ramp 13 increases the speed of the water in water circulation cells established on the adjacent beaches, under the ramps 3, 3 ′, “e-which still activates the heat exchange. Other positions could however be chosen for the watering booms. Thus, for example, the boom 13 could be split into two booms 13 _{1 #} 13 ₂ , arranged in the vicinity of a spray boom 3 ', with a flow by gravity of the irrigation water, directly on the range of the sheet metal on which the ramp 3 'diffuses water spray. According to a variant, the ramp 13 could also be split into two ramps 13 ₃ , 13__, arranged like the ramps 13_., 13 ₂ , with an oblique forced flow in the range which receives water sprayed from the ramp 3 for example . The ramps 13__, 13 ₂ , or 13 ₃ , 13 ₄ , are preferably dimensioned so as not to obstruct the air passages provided around the ramps 3, 3 ', etc. As indicated in French patent 2,578 .553 above, these provisions allow the fan connected to the suction chambers 6 to draw secondary air passing around the ramps 3, 3 ', which promotes the evacuation of the spouting water.

We will now describe the water sprinkling means incorporated in a head module of the installation according to the invention, to increase the heat flux on the lower surface of the sheets which pass through the installation. For this, reference is made to FIG. 4 which represents in more detail one of the booms 4, 4 ′ shown diagrammatically in FIG. 2 and the spraying means in sprayed water associated with this baffle to obtain a quenching of a circulating sheet 2 on the rollers 1, 1 ', 1 ", ... in cooperation with the sprinkling means which have just been described with the aid of FIGS. 2 and 3. Thus, in this figure, we find the spraying boom 4 and the beams 11, 11 ′ supporting a deck cross member 10 installed between two rollers Successive 1, the via of spacers 22 ^*, 22 '. The spraying boom 4 is of the type described in the aforementioned French patent No. 2,578,449 and comprises a spraying head having a pressure water injection slot 18 and two adjacent air injection slots 19, 19 ′ compressed to spray the water leaving the slot 18 homogeneously in a prismatic volume 20 so as to sprinkle the underside of a sheet 2 circulating on the rollers 1, l ', with water spray. As we saw above, obtaining a quenching of this sheet requires an additional supply of water on both sides of it, at least in the head module of the installation. Additional watering means for the underside of the sheet 2 are therefore provided for this purpose in this module. According to an advantageous characteristic of the present invention, these sprinkling means are incorporated in the beams 11, 11 'which serve as supports for the decking crosspieces 10, 10'. To this end, the beams 11, 11 ′ are hollow and supplied with water under pressure by means (not shown) to constitute means for supplying water to distributor tubes 21, 21 ′ which plunge into these hollow beams at through their top wall.

This arrangement is advantageous in that the external geometry of the members located under the sheet is not modified compared to that of the original installation. Thus, when a treatment of this cooling of the sheet does not require an additional supply of non-sprayed water and the supply of the means arranged for this purpose is then cut off, the spraying of water produced by the ramp 4 remains exactly the same as that observed in an installation not equipped with water supply means (11, 11 ', 21, 21'). Thus the settings that have been established for the water sprayed in such an installation remain valid. We will see below that maintaining the validity of these settings is also important in

Adjusting the installation to such a cooling speed profile, corresponding to such desired quenching. Preferably, as shown in FIG. 4, the upper ends of the distributor tubes 21, 21 ′ are inclined so that the unsprayed water is projected onto the sheet, passing through spaces located between the spray field 20 of the boom. 4 and rollers 1, respectively.

FIG. 4 also shows means for masking (23, 23 ′) of the water jets emitted by the ramp 4 and the distributor tubes (21, 21 ′). These means comprise two pairs of plates 23, 23 ′ secured by a spacer 24, each pair being movable transversely relative to one of the edges of the sheets 2 to be treated, by interposing between predetermined lateral parts of these sheets and the ramp 4 on the one hand, the tubes 21, 21 'on the other hand. It is thus possible to adjust the width of the surface of the sheet which is wetted by limiting "edge" effects liable to accelerate unfavorably the cooling of the edges of the sheet. Similar masking means (not shown) are provided to cooperate with the upper ramps 5, 5 'so as to act on the edges of the upper face of the sheets, for the same purpose.

It is now understood that, in the head modules of the installation where the sprinkling means (13, 16) and (11, 11 ', 20, 20') are placed in water, the additional supply of water can be such that the cooling speed of the sheet can be accelerated substantially so as to obtain a quenching effect necessary for the treatment of the metal constituting certain sheets (see FIG. 1).

According to the present invention, these sprinkling means are supplied at a constant flow rate and it is by adjusting the flow rate of water sprayed by the ramps 3, 3 ′ etc. and 4, 4 ′ etc. adjusts the total water flow so as to obtain this or that desired quenching profile. This strategy takes advantage of the fact that it is perfectly known how to regulate the flow rate of sprayed water and that this flow rate is not disturbed by the installation of the water sprinkling means, implemented in the invention. According to the invention also, knowing the maximum flow rate of the sprinkler installation, the constant flow rate of the sprinkler means is fixed at a value such that the sum of these flow rates ensures the hardest quenching of the thickest, widest and warmest sheet which must pass through the installation, that is to say to ensure the quenching requiring the greatest heat exchange with the cooling water. Various sheet cooling strategies, with or without quenching, are then possible in the installation according to the invention, as will now be explained in connection with the diagram in FIG. 5 where the flow rates d have been shown. water used, module by module, according to different typical operations. For this diagram, an installation with five modules M _x to M ₅ has been chosen, the two head modules M _x and M ₂ being equipped with additional water sprinkling means according to the invention. The fixed flow rate of these means, established as described above, and the adjustable flow rate of the spray bars were identified on the ordinate axis.

A dashed line shows a conventional operation of the installation, the water sprinkling means being cut off. The water spray rate is, for example, adjusted to 4/5 of its maximum value in the modules M _lr M ₂ and M ₃ to fall to 3/5 in the module M ₄ and to 2/5 in module M ₅ . It is thus possible to obtain a cooling profile having the appearance of that shown in solid lines in FIG. 1.

We now place ourselves in an extreme case, where the installation must ensure the strongest possible quenching, on the thickest, widest and warmest sheet which must pass, in the installation. The corresponding flow rates of the -modules are marked in solid lines in FIG. 5. In the modules M _j . and M ₂ , the flow of water spray is brought to its maximum and, adding to the fixed flow of water sprinkling means which are then activated, makes it possible to establish in the modules M _x and M ₂ , a flow total maximum clean water to obtain the desired quenching. In modules M ₃ , M ₄ and ₅ , the water flow can, for example, be maintained at the maximum flow of water sprayed.

The flow rates to be established in the different modules are shown in phantom in the graph of FIG. 5 when it is desired to cool with quenching, the heat exchange necessary for quenching less intense than that envisaged in the previous case. If the total water flow in the modules Y- and M ₂ is equal to 8/5 of the maximum sprayed water flow, as shown by way of example in FIG. 5, this flow can be reduced for example to 6 / 5 by an adequate adjustment of the sprayed water flow rate, keeping the fixed flow rate of the spraying means at the value of 3/5 of the maximum sprayed water flow rate chosen by way of illustration. Thus according to the invention, the adjustment of the total water flow in the modules M__ and M ₂ equipped for quenching is done by subtracting a fraction of the flow of sprayed water and not by modulating the water flow watering. This takes advantage of the experience of adjusting the flow rate of water sprayed by the personnel operating the installation, experience drawn from their practice of an installation not provided with the sprinkling means provided by the present invention. In modules M ₃ , ₄ and M ₅ the sprayed water flow can be set to 4/5 of the maximum possible flow, for example.

It now appears that the cooling installation according to the present invention achieves the objectives which we had set ourselves, namely to provide a cooling installation of the type described in the aforementioned patents, with an optional capacity. quenching which does not disturb the operation of this installation when this capacity is not used. The flexibility of use of the installation is thereby increased. Furthermore, the method of adjusting the total water flow in the head modules, by action on a sprayed water flow, the adjustment of which is well controlled, allows to precisely adjust the installation to obtain this or that desired quenching.

Claims

1. Process cooling in parade with quenching of flat products, in an installation where these products pass between two rows of water spraying booms with adjustable flow, arranged transversely to the direction of travel of the products in a plurality of adjacent modules, characterized in that the two faces of the products are additionally sprinkled, as they pass through at least one module located at the head of the installation with a flow of irrigation water fixed by construction such that the sum of this fixed flow and the maximum sprayed water flow rate possible in this module ensures the greatest heat exchange of quenching to be carried out in said module, and in that a desired quenching is established by adjusting the flow rate of water sprayed into said module. 2. Installation for implementing the method according to claim 1, comprising means for passing flat products (2) between two rows of ramps (3, 3 '; 4, 4') for spraying water to adjustable flow rates arranged transversely to the direction of travel of the products, in a plurality of adjacent modules distributed over part of the path followed by the products, characterized in that it comprises, in at least one (lΛ _lt M ₂ ) of the modules placed at the head of the installation, means (11, 11 '; 12, 12'; 13) for watering the two faces of the products with irrigation water at a flow rate fixed by construction, determined so that it ci, added to the maximum flow of water spray possible in said module, ensures the highest heat exchange to be achieved in this module. 3. Installation according to claim 2, wherein the products pass substantially horizontally on a path defined by rollers (1, l ', 1 ") of support and drive, suction boxes (6) being interposed between the spray bars (3, 3 ') arranged above the product path, characterized in that said sprinkling means comprise at least one ramp (13) for distributing water on the upper face of the products, installed in a suction box (6) so as to clear around this ramp a space allowing a suction of moist air by the box. 4. Installation according to claim 3, characterized in that the ramp (13) of water distribution is transverse to the trajectory of the products, the water arriving on the products by overflow (16 ') and flow by gravity. 5. Installation according to claim 3, characterized in that the ramp (13) of water distribution is transverse to the path of the products, this ramp being equipped with a series of distributor tubes (16) regularly staggered and plunging into the ramp (13) so that their supply can be cut by a controlled drop in the water level in the ramp (13). 6. Installation according to claim 2, in which the products pass substantially horizontally over a trajectory defined by rollers (1, 1 ′, 1 ") for support and drive, suction boxes (6) being interposed between the spray bars arranged above the product path, characterized in that said sprinkling means comprise at least one boom (13 _j _, 13 ₂ ; 13 ₃ , 13 ₄ ) for distributing water from sprinkling on the upper face of the products, installed in a space provided between a ramp (3, 3 ') for spraying water and a wall of a compartment containing this ramp, providing a space allowing additional air circulation between this ramp and this wall, towards the suction boxes. 7. Installation according to any one of claims 3 to 6, characterized in that said sprinkling means further comprise at least one ramp (11, 11 ') for supplying water arranged in the path of the products and equipped with a series of distributor tubes (21, 21 ') regularly staggered transversely to water the underside of the products (2), these rarcpes (11, 11') being shaped as support for guide means (10, 10 ') of these products (2), between two adjacent rollers (3, 3', 3 "). 8. Installation according to any one of claims 3 to 7, characterized in that the sprinkling means bring unsprayed water onto surfaces of the products located outside the fields of the water spraying booms. 9. Installation according to any one of claims 7 and 8, characterized in that it comprises means (23, 23 ') movable transversely to the path of the products, to selectively mask the edges of the faces of these products vis- vis-à-vis the means for spraying water and means for sprinkling with non-sprayed water.