PROTECTION ARRANGEMENT FOR USE IN A HOT ROLLING MILL

Abstract: To protect a heat shield arrangement over of a hot-rolling mill, at the entry end of the table contact members (14) of large mass are suspended over the path of the hot material (M) to form a height barrier for distorted material. The members are suspended displaceably from bars (30) on a cantilevered support (12) that leaves one side of the table (2) open for the removal of scrapped material. The bars (30) pass through contoured apertures (32) in the members which permit the members to move in forwards and upwards so that when struck by the material they can lift and can also yield to the frictional force of the material travelling under them. The loading on the cantilevered support is thereby reduced. Reduction in peak loadings also result from mounting the members (14) on an upwardly pivotable cantilever frame (12, 60) and by damping the return movements of the members and/or the frame.

Description: This invention relates to the handling of strip material, which term as used herein includes slabs and like generally planar material. It is concerned particularly, but not necessarily exclusively, with the handling of material in steel processing plant, such as hot strip mills, where the material may require to be progressed along conveying means through successive process stages or to be deposited and held at a particular station between stages. It is known to provide a heat shield arrangement in a hot strip mill to control the temperature of the strip or slab on a roller table between processing stages. To protect the heat shield arrangement from damage by material that has been distorted to a non-­ planar state, it is known (EP 0042656) to place a reinforced frame or plate guide structure at an entry region of the roller table preceding the heat shield arrangement over the main length of the table, this structure providing an increased-height passage for the introduction of turned-up material. The passage decreases in height as it leads into the main region of the heat shield arrangement where there is a space of limited height between the table and the heat-shielding panels overlying the table. The entry structure has a very robust construction so that it offers considerable resistance to impact and thereby at least partially corrects any turn-up of the entering material that causes the material to contact it with force, so protecting the more fragile heat-shielding panels that follow it. Another form of height barrier for an entry guide structure that has been in use in the British Steel Corporation plant at Lackenby, Lincolnshire, England, comprises contact means in the form of a large mass suspended above the roller table from a gantry or support frame which straddles the table. The mass is composed of a series of parallel, vertical steel slabs fixed together by transverse tie rods and extending along the roller table. The slabs are mounted on cylindrical transverse members of the support frame which pass through clearance holes in the slabs of a slightly larger diameter than the diameter of the members to allow the slabs a limited amount of free vertical movement on the support frame if struck with sufficient force by incoming material so as to limit the maximum upward impact force that will be experienced by the entry guide structure and/or the material. It will be clear that this previously used arrangement can nevertheless only have a limited effect in reducing the shock loads that may be transmitted to the supporting frame and the adjacent regions of the roller table foundations if it is to be effective in reducing the turn-up of the leading edges of strips. It is not only a question of giving the slabs scope for vertical movement, because the further they are allowed to rise the further they then fall. If the loading caused by material striking the guide structure is reduced by using the energy to lift massive slabs, downwards shock loads then result as the slabs fall into place again. The problem of accommodating large impact loads from such a barrier becomes especially acute if a clear space is to be left at one side of the roller table, e.g. as an outlet path for scrapped or damaged material. Such a requirement means that the contact means must be carried by a cantilevered support frame and as a result the possible impact loading the contact means can impose on the frame becomes far more critical. If a protective entry guide structure is to be fitted to an existing installation, it will usually be necessary to secure the cantilever arm rigidly to the base structure of the roller table, which then has the added duty of supporting the full load of the system in operation, but even if the entry guide can be mounted independently, e.g. on cross members extending under the roller table, as may be more easily possible in a new installation, there is a need to limit the effects of shock loads. According to one aspect of the invention, there is provided an entry guide structure comprising at least one contact member suspended from a support extending above the material path to form a massive barrier at a spacing above said path, said barrier being upwardly displaceable when impacted by entering material, said at least one contact member being displaceable obliquely forwards and upwards relative to the material path when impacted by material entering said path, and damping means being provided for retarding the rate of descent of said contact member from a raised position of displacement. In this way after said contact member has been lifted by passing material the peak loading imposed on the support frame in its descent is reduced. Preferably said damping means are so connected between said at least one member and a support frame on which said member is suspended, as to allow longitudinal displacements of said member relative to the support frame; such an arrangement can complement the provision of means for permitting free upward and forward movement of the member. According to another aspect of the invention, there is provided an entry guide structure comprising at least one contact member of large mass suspended above the material path from mounting means on which said at least one member is upwardly and downwardly displaceable, the or each such member having openings with downwardly directed bearer faces through which the member rests on the mounting means, said faces being forwardly and upwardly inclined with a major portion at an angle less than 45° to the horizontal. The rest position of the mounting means is thus at a forward region of such a face and from that rest position said at least one contact member is obliquely movable forwardly and upwardly relative to said material path, whereby it is freely displaceable in said oblique direction when struck by the material entering onto the supporting means. With such an arrangement, the means of mounting the contact mass are specifically arranged to leave clearance for movement under the action of lifting forces and also substantial horizontal friction forces, so that impacts from both sources can be minimised or avoided. According to a further aspect of the invention, there is provided an entry guide structure in which at least one massive contact member is displaceably suspended over the material path from a cantilevered support whereby the material path at said entry guide is laterally accessible from one side, the contact member or members being upwardly displaceable on said support, and the support is mounted on pivot means in a manner permitting its displacement upwards from a normal operating position, in response to upward impact forces on said at least one contact member, in addition to said displacement of the member or members on the support. By such means it is possible to ensure that in the event of a large impact forcing the contact members to travel the full extent of the movement provided for, a limit is set to impact loads that may be transmitted to the support frame. Embodiments of the invention in its application to a steel hot-rolling mill will be described by way of example with reference to the accompanying diagrammatic drawings. Figs. 1 and 2 are rear and side views, respectively, of a first construction in accordance with the invention, and Fig. 3 is a rear view of another construction in accordance with the invention. Referring to Figs. 1 and 2, there is shown a conventional roller table with rollers 2 supported on mountings 4 to span a flume 6 in the foundation works of a hot-rolling mill. Material M enters the table in strip or slab form to travel longitudinally through an entry structure at the beginning of the table before passing into a tunnel-like heat shield (not shown) that surrounds the remainder of the length of the table. The entry structure comprises a support frame composed of braced pillars 10 at one side of the roller table from which a rectangular sub-frame 12 spanning the longitudinal extent of the pillars projects across the table in the manner of a cantilevered beam to carry a series of steel slabs 14 of large mass suspended side-by-­ side in parallel over the table. The rigidity of the sub-frame is increased by a top cover 16 extending over the slabs 14. Further strengthening is provided by a series of transverse diaphragms consisting of C-form front and rear diaphragms 18 with top and side limbs welded to the sub-frame and pillars respectively and bottom limbs extending across the flume between rollers, and intermediate L-form diaphragms 28 similarly welded to the pillars 10 and having bottom limbs extending across the flume. The massive slabs 14 are supported on the sub-frame 12 by mounting bars 30 which pass through profiled apertures 32 in the slabs described in more detail below. Tie rods 34 pass through the steel slabs 14 to hold them as a unit for movements in their own planes as a unitary barrier suspended at a desired height over the roller table. Front and rear extensions 36 of the slabs connect them to dashpots 38 (shown in Fig. 2 only) held on brackets 40 fixed to the sub-frame 12. The slabs are each of identical form with inclined lower edges 46 that include a first steeper portion and a following portion at a shallower inclination. The slabs present an obstacle to distorted strip entering the table; if the strip has a large turn-up at its leading end this will strike the first, steeper portion of their lower edges and because of the considerable mass of the slabs a correspondingly large reaction force is experienced by the strip tending to flatten the turn-up. The smaller inclination of the following portion of the slabs is intended to prevent excess friction causing buckling of the following length of the strip, or to correct strip which has only a small turn-up at the head end. The combined inclinations along the length of the slabs is sufficient to ensure that no strip passes the entry section so distorted that it will damage heat shield panels overlying the following region of the roller table. The maximum impact forces experienced by the slabs can be expected to exceed their weight although they will be made suitably massive, but such forces are at least largely isolated from the support frame because the apertures 32 in the slabs through which the mounting bars 30 pass allow the slabs to be lifted from the sub-frame 12. The inclined form of the upper rear portion 32a of the slots ensures that none of the impact load is transferred to the support structure despite the fact that the displacing force experienced by the slabs can have a considerable horizontal component due to the movement of the strip along the roller table. The horizontal component can be similar in magnitude to the lifting force of the impact, but the inclination of each upper rear portion 32a of each aperture is substantially less than 45°, so that the slabs are kept clear of the mounting bars as they are lifted. The preferred inclination will depend on a number of factors and may vary from one installation to another, but preferably, the profile of the portions 32a is so chosen that they remain close to the mounting bars as the slabs move forwards and upwards. In this way any downwards impact from the fall of the slabs when the strip runs free of them thereby being minimised. The drawings show rectilinear faces 32a, which are relatively convenient to form, but the desired conditions may be more precisely met by slightly curved faces the slope of which reduces towards their lower, rearward ends. In the illustrated example, the leading face 32b of each aperture extends vertically from the apex of the aperture so that the drop distance is kept to a minimum when the slabs are allowed to fall again. It may be of advantage to incline the front edges of these slots forwards and downwards to facilitate clearing the entry section if, in an extreme case, material becomes jammed under the slabs after the slabs have been lifted to bring the bottoms of the apertures 32 against the mounting bars 30. When the jammed strip is then pulled rearwards the inclination of the front edges would allow the slabs 14 to be more easily lifted by the friction force from the strip. As a further measure to limit the maximum loading on the support structure, the dashpots 38 are able to control the rate of descent of the slabs from a raised position and so limit any downward impact force. The dashpots are so arranged that the downward fall of the slabs is cushioned while imposing the minimum resistance to upward travel. Since the slabs 14 move longitudinally as well as upwards, the dashpots are connected through pivot connections 52, 54 so that they can rock freely forwards and backwards with the slabs and it will be clear that they also do not hinder forward travel of the slabs. The example illustrated in Fig. 3 is similar in many respects to the construction already described. In addition, however, the cantilevered sub-frame 12 is now mounted on pillars 10a through a longitudinal pivot 60 so that it can tilt upwards from a normal position in which it rests on bearing pads 62 on the C-frames 18a. The sub-frame has a lateral projection 64 beyond the pivot 60 and an arcuate guide slot 66 in the projection 64 receives a fixed pin 70 on a separate support 72. In the event of a severe impact on the slabs 14 that cannot be wholly countered by the clearances in the apertures 32, the sub-frame 12 can now lift as a whole, keeping the impact load from the pillars and the roller table foundations. A dashpot 74 is preferably connected between the sub-frame and the pillars to cushion the fall of the sub-frame. Although the arcuate slot 66 will set a limit to the upward pivoting of the sub-frame, it is of a length to ensure its effect will not normally come into operation. Should the fixed pin reach the end of the slot in the rise of the sub-frame a downward impact is delivered to the support 72. However, the support is set further from the roller table and its foundation can be more easily reinforced against impact loads. Whereas the first example showed the entry structure in combination with a conventional roller table and foundation, illustrating that the invention can be applied to an existing installation, Fig. 3 indicates that when the invention is applied to a new installation it is possible to integrate the entry structure with the roller table support to give additional strengthening to the entry structure. Specifically, as compared with Fig. 1, Fig. 3 shows the end C-frames 18a (and similarly the intermediate L-frames) can have a larger bottom limb adding substantially to their load-bearing capacity. Because of the pivotability of the sub-frame 12 over the C-frames 18a, the top limbs of these of course simply provide bottom supports for the sub-frame, transmitting down loads only.

Claims: 1. Apparatus for use in handling a heated strip or slab of material in a rolling mill comprising supporting means (12) providing a longitudinal travel path for the material and at an entry end of said supporting means an entry guide structure comprising at least one contact member (14) suspended from a support extending above the material path to form a massive barrier at a spacing over said path , said barrier being upwardly displaceable when impacted by entering material, characterised in that said at least one member (14) is displaceable obliquely forwards and upwards relative to the material path when impacted by material entering said path, and that damping means (38) are provided for retarding the rate of descent of said contact member from a raised position of displacement. 2. Apparatus according to claim 1 wherein the mounting means for said at least one member comprises a cantilever support to one side of the travel path leaving the path at said entry end directly accessible laterally from the other side. 3. Apparatus according to claim 2 wherein said support comprises at least one cantilevered upper limb of a C-­ frame structure (18) having a base limb extending below the material path. 4. Apparatus according to any one of claims 1 to 3 wherein said at least one member is suspended by apertures (32) in it each having a forwardly and upwardly inclined bearer face extending at least approximately in the direction of displacement of said member. 5. Apparatus according to claim 4 wherein the angle of inclination of said bearer faces is less than 45° to the horizontal. 6. Apparatus for use in handling a strip or slab of material in a rolling mill comprising supporting means (12) providing a longitudinal travel path for the material and at an entry end of said supporting means an entry guide structure comprising at least one contact member (14) of large mass suspended above the material path from mounting means (10,12,30) on which said at least one member is upwardly and downwardly displaceable, the or each member (14) having a plurality of openings (32) through downwardly directed bearer faces (32a) of which the member rests on the mounting means, characterised in that said downwardly directed faces (32a) of the contact member openings (32) are forwardly and upwardly inclined relative to the material travel path, at least a major part of each said face being at an angle less than 45° to the horizontal whereby the rest position for the mounting means (30) on said face is at a forward region of said face, from said rest position said at least one contact member being obliquely movable forwardly and upwardly relative to said material path, whereby it is freely displaceable in said oblique direction when struck by the material entering onto the supporting means. 7. Apparatus according to claim 6 wherein unidirectional damping means (38) are connected to said at least one contact member so that said member is freely movable forwards and upwards but is retarded in the opposite direction. 8. Apparatus according to any one of claims 4 to 7 wherein extending from the top regions of said bearer faces (32a) the apertures have end faces that are substantially vertical or that are inclined downwardly and forwardly from the vertical in the direction of material travel. 9. Apparatus for use in handling a strip or slab of material in a rolling mill comprising supporting means (12) providing a longitudinal travel path for the material and at an entry end of said supporting means an entry guide structure comprising at least one massive contact member (14) displaceably suspended over the material path characterised in that said contact member is suspended from a cantilevered support (12) known per se whereby the material path at said entry guide is laterally accessible from one side, the contact member or members being upwardly displaceable on said support, and the support (12) is mounted on pivot means (60) in a manner permitting its displacement upwards from a normal operating position, in response to upward impact forces on said at least one contact member, in addition to said displacement of the member or members on the support. 10. Apparatus according to claim 9 wherein damping means (74) are provided for retarding the rate of descent of the cantilevered support (12) from a raised position. 11. Apparatus according to claim 9 or claim 10 wherein said at least one contact member is displaceable on said support forwardly and upwardly relative to said travel path, and the axis of the pivot means extends in the direction of said travel path. 12. Apparatus according to claim 11 wherein the or each contact member (14) is suspended by mounting means (30) passing transversely through apertures (32) in said member, said apertures having upper bearer faces (32a) that are inclined upwardly in the direction of material movement. 13. Apparatus according to any one of the preceding claims wherein the or each contact member has a lower edge (46) that is inclined downwardly in the direction of material travel into the entry region. 14. Apparatus according to claim 13 wherein the inclination of the lower edge (46) is greater at an upstream region of the lower edge than at a downstream region thereof.

Inventors: LAWS, WILLIAM ROBERT, REED, GEOFFREY RONALD
Applicants: ENCOMECH ENGINEERING SERVICES LIMITED
Application year: 1986
Main classification: B21B33
IPC codes: B21B45, B21B1, B21B39, C21D9