LU84041A1 - IMPROVEMENTS IN PROCESSES FOR WIDTHING OF SLABS - Google Patents

Description

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BL-3292 / EM / BM

Claiming the priority of a patent application ζ filed in Belgium on April 1, 1982 with No. 6 / 47,425 and issued under, No. 888,239 ”-ίο 2123/8104.

METALLURGICAL RESEARCH CENTER -CENTRUM VOOR RESEARCH IN DE METALLURGIE,

Non-profit association -Vereniging zonder winstoogmerk in BRUXELLES, (Belgium).

Improvements to the processes for setting the width of the slabs.

The present invention relates to improvements to the methods for setting the width of the slabs.

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The manufacturing process of steel products, such as · 5 sheets or wide strips is essentially conditioned by two parameters which are both fixed for different reasons, the first one being the width of the finished product (sheet or wide strip) is imposed by the customer, the second, the width of the starting slab is imposed either 10 by the dimensions of the ingot mold in the case of a continuous casting installation of steel directly in the form of slab, or by the dimensions the most frequent that the roughing train gives to the slab that it delivers.

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I The problem that the laminator therefore has to solve consists, starting from a slab of given section, to arrive at a sheet J or wide strip of imposed width, and this in the "most advantageous way possible at any point of view.

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One of the parameters conditioning the advantageous nature of the sequence chosen to pass from the slab to the finished product is constituted by the number of width reductions that one is brought to achieve, another by the proportion of the 10 falls that must be consent during the said sequence.

In the particular case of continuous casting, it is obviously sought to change the mold as often as possible, so as to obtain the maximum production from the machine; the ideal result in this case would be to be able to use only one width in the mold, corresponding to only one slab width, namely the maximum width I.

120 In order to keep the number of width reduction operations as small as possible, it must be ensured that each reduction phase is as large as possible, that it is carried out in an additional cage placed downstream of a continuous casting machine, either in the roughing train itself.

However, we are currently limited in the reduction possibilities that can be achieved in a single operation, both in one and in the other case. Indeed, in a roughing rolling mill, it is rarely possible to exceed 100 mm of reduction without deforming (causing the rectangular shape to lose) the slab, which constitutes an important cause of falling, and in an additional cage, the risk of loss of The rectangular shape of the slab increases with the thickness of the slab. We are therefore faced with a dilemma, each of which has a drawback i - 'Ί

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* - 3 - major, either accept a significant drop in the steel, but benefiting from a small number of reduction phases, or accept a greater number of reduction phases (with little deformation of the ends of the slab) , but in 5 benefiting from less fall.

The object of the present invention is precisely a process which makes it possible to avoid this dilemma, that is to say to achieve significant reductions in width, while retaining the slab in a practically rectangular shape.

The principle applied in this process consists essentially in the fact that a phase of reduction in width retaining a practically rectangular shape with the slab is obtained by subjecting the said slab to at least two successive operations, each of these two operations performing a deformation of the slab, but the deformation from the second operation restores to the slab the rectangular shape which the deformation due to the first operation had made it lose.

It goes without saying that preference is given to a reduction sequence comprising only two successive deformation operations, the second compensating for the effect of the first, but it is not outside the scope of the present invention, to consider a reduction sequence comprising more than two operations, the deformations of which they bring to the slab are self-compensating, in whatever manner.

The application of this process to slabs consists in passing the slab first: _a. between two rolling mill rolls, at least one of which, preferably both, has a profiled beam, so as to reduce only the edges / of the slab, "" Ή.

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- 4 - î b. between two lateral cylinders (known as discharge cylinders), also ij || ment in rotation, compressing the ends of the slab,

Iet imparting a deformation to them, such that at the said ends, the material displaced under the effect of the compression comes (taking into account the reduction in width), occupying the reduction zone which the said had printed ends, the passage between the cylinders listed under _a.

10 The passage of the slab between the cylinders listed under a. shows an axial compression component in the slab, which has the effect of pushing the material from the latter towards its central part, with a certain increase in thickness of the slab in the part not touched by the cylinders . It goes without saying that the effect of deformation due to the passage of the slab between the cylinders listed under b. restores the ends of said slab to a thickness corresponding to that of its new central part, so that the section of the slab thus remains well rec-20 tangular after the reduction of width phase. To effectively obtain such a result, it may be necessary to give the generator supply cylinders an appr pro riate pro le.

The field of the present invention also covers any rolling mill comprising one or more rolls, the generators of which would conform to the description given above, whatever their actual profiles, or the association of which would achieve self-compensating effects de-formation 30, allowing to maintain practically a rectangular shape to the slab, after its passage between said cylinders.

The diagrams below, given by way of example, without any character of limitation, and not to scale, allow I to realize more, how the process of the invention actually allows to obtain the desired result.

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In this drawing of Figure 1, there are shown, very schematically, two rolling mill cylinders 1 and 2, axes 3 and 4. Between these two cylinders, the ends 5, 6, 7 and 8 are flared by relative to their part cen-5 milking 9 and 10, a slab 11 is passed whose profile 12 is such that its ends are subjected to compression from the ends 5 to 8 of the cylinders. These ends take a frustoconical shape 13,14, while the central part of the slab, under the effect of the axial component 10 of compression (15) due to the shape of the ends of the cylinders, increases slightly in thickness, which passes from 16 in 17.

This first rolling phase is followed by a second phase in which the slab has at this moment a cross section whose shape is given in FIG. 2.

This section is subjected to axial compression by means of two rotary delivery cylinders 18 - 19 with axes 20 and 20 21 whose simultaneous displacement, the first along arrow 22, the second along arrow 23, compresses the ends of the slab and gives them the profile 24 - 25 by lateral discharge of the material contained in the ends 26-27. The rectangular shape of the slab is thus preserved.

This example relates to an operation carried out in two phases, but, as said above, it is not beyond the scope of the present invention to achieve, in more than two phases, the maintenance of this almost rectangular shape with 'compensation for deformations .

Claims (3)

1. A method of rolling a slab, characterized in that said slab is subjected to at least two successive operations, each of these two operations deforming the slab, but the deformation coming from the second operation restoring to the slab, the rectangular shape that the deformation due to the first operation had made him lose. * ‘10 1 Patent claims. s 2. Method according to claim 1, characterized in that the first rolling operation compresses only the edges of the slab and the second only performs a compensatory discharge of the edges thus deformed. : i5 3. Method according to either of claims 1 and 2, characterized in that preference is given to a reduction sequence comprising only two successive deformation operations, the second compensating for the effect of the first. 1 2 Slab rolling device, characterized in that it successively comprises one behind the other: a. two rolling mill rolls, at least one of which, and preferably both, have a profiled generation so as to reduce only the edges of the slab, b. two cylinders (said repressors) also in rotation, compressing the ends of the slab and imparting to them a deformation such that at said ends the material displaced under the effect of compression comes, (taking account of the reduction in width), occupy the reduction zone that the passage between the rollers listed under a. printed at the said ends. 35 2 Processes and rolling mills as described above. —- 11 -