Metal working – Plural diverse manufacturing apparatus including means for... – Binding or covering and cutting
Reexamination Certificate
1999-03-22
2001-09-04
Bishop, Steven C. (Department: 3722)
Metal working
Plural diverse manufacturing apparatus including means for...
Binding or covering and cutting
C072S039000, C072S201000, C072S203000, C072S234000, C164S263000, C164S417000
Reexamination Certificate
active
06282767
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention concerns a method to roll strip and plate and the rolling line which performs this method.
To be more exact, the invention arranges to produce strip or plate by starting from thin slabs consisting of steel or of a metallic alloy and produced by means of continuous casting, thus obtaining a product of a high surface and internal quality.
Thin slabs to which the invention is applied have a thickness between 70 and 110 mm.
The rolling line according to the invention is able to tend a casting machine having at least one line.
In the-case of two casting lines, they are fed at the same time, thus optimising the yield and efficiency of the plant and especially the yield of the rolling train.
In the field of rolling and, in particular, in the production of strip and/or plate, the problems are well known which are encountered by producers in obtaining a product of a high quality and in using at the same time a production line characterised by great functionality, versatility, good use of space and by fast and reduced times spent on corrective work for maintenance and replacement.
The state of the art also covers rolling lines, such as that in European patent application No. 951028.81.0 for instance, which are fed alternately by two or more continuous casting machines; these lines normally include systems for transferring the products from the casting line or lines positioned offset from the rolling line.
The transfer systems are normally obtained with modular elements forming part of a furnace performing temperature maintenance and possible heating of the segments of slabs coming from the relative continuous casting line.
In these rolling plants associated with at least two continuous casting machines one furnace is normally in-line and feeds the segments of slab to the rolling train, while the other furnace acts as a buffer store and maintains the temperature of the segments until they are sent to the rolling train.
In such a case, since the rolling train and continuous casting machine normally work at different speeds, interruptions of the feed to the rolling train take place between one segment of slab and the next one.
This fact not only entails a reduction of the yield of the whole plant but also involves the great risk of damage and wear to the rolling rolls owing to continuous alternate stresses arising from a very discontinuous processing.
Moreover, complex and bulky systems are required for the buffer store and for traversing so as to contain and to transfer the segments which gradually accumulate on the casting line acting as a buffer store at that moment.
Furthermore, the traditional plants include two distinct systems for feeding the molten metal to the mould, each system being equipped with its own ladle.
This involves a great overall bulk, the possibility of contacts between the two systems, less space for possible work to maintain and/or replace the components and also working difficulties connected with the discharge of the molten metal into the two different mould systems.
Another aspect which characterises the plants of the state of the art concerns the descaling systems included in-line.
The plants of the state of the art normally include descaling systems with stationary water walls positioned at the outlet of the temperature-maintaining and/or heating furnaces.
These embodiments not only entail a great waste of water but also are incapable of eliminating all the scale which forms on the surface of the products being rolled, especially in the normal case in which the scale formed consists mainly of hard oxides owing to the low speed of feed and the high temperature.
If the segment of slab entering the furnace has on its surface a great quantity of scale, the layer of scale increases considerably within the furnace and, in view of its content, is very difficult to remove.
SUMMARY OF THE INVENTION
The present applicants have designed, tested and embodied this invention so as to overcome, or at least to reduce partly, these shortcomings of the state of the art and to achieve further advantages.
The purpose of the invention is to embody for strip and/or plate a rolling line which achieves the twofold result of producing a product of a high surface and internal quality by means of a line characterised by high yield, flexibility, excellent use of the space available and of the overall bulk, and versatility.
The rolling line according to the invention comprises a casting machine having at least one line.
According to a variant, the casting machine has two lines working at the same time and being fed simultaneously.
According to this variant, the moulds of the two casting lines are fed at the same time by one single ladle equipped with relative conduits for discharge of the molten metal.
In this way the overall bulk of the casting machine is reduced; there is the security of the simultaneous progress of the casting and of the uniformity of the cast product and the uniformity of its temperature; and also the possible work of maintenance and/or replacement of the components of the casting machine is simplified.
A shears is included immediately downstream of the casting line and shears the cast slab into segments of a desired length, which are accelerated at once within the respective furnace systems performing heating and possible temperature-maintaining.
According to the invention fast heating means, of an induction type, for instance, are included between the shears and the inlet of these furnace systems and are followed by a descaling means.
According to the invention the descaling means is of a rotary type with a high pressure of delivery so as to achieve a saving of the water delivered, while ensuring at the same time the effectiveness of the action and its uniformity over the whole surface of the slab.
According to the invention the furnace systems are of a type with independent modules having independent heating systems incorporated.
This situation enables the flexibility and versatility of these systems to be increased considerably according to the type of the cast product and according to the production rate.
Each of the modules forming these furnace systems has a length at least equal to that of the segments of slab prepared by the shears.
According to the variant of the invention the furnace systems included on each of the two casting lines have their last downstream module associated with a traversing system able to transfer the module to a position on the axis of the rolling train.
In particular, according to the invention, as soon as the segment has left the last downstream module of the furnace system and has been sent to a roughing rolling mill stand and thence to a finishing train, the last downstream modules of the furnace systems of the two lines, are exchanged for each other so as to position on the. axis of the rolling train the module containing the segment of slab.
The speed of exchange of the last downstream modules of the furnace systems is synchronised with the casting rate and with the speed of acceleration so as to achieve in this way a substantially continuous feed to the rolling train.
The rolling line according to the invention comprises, downstream of these furnace systems, a descaling unit, a roughing rolling mill stand able to reduce the thickness of the slab to the most suitable value for the working of the finishing train, a further tunnel furnace performing at least temperature-maintaining and then the finishing train preceded by a further descaling unit.
The finishing train is then followed conventionally by a cooling conveyor and a winding unit.
The embodiment according to the invention not only optimises the yield and efficiency of the plant and increases its output but also enables the downtimes of the rolling rolls between one working cycle and another to be reduced and thus improves the yield of the-rolls and reduces their wear.
REFERENCES:
patent: 3478808 (1969-11-01), Adams
patent: 4898227 (1990-02-01), Benedetti et al.
patent: 4920899 (1990-05-01), Blundy
patent: 5276952 (1994-01-01),
Borsi Roberto
Fasoli Fabio
Anotnelli, Terry, Stout & Kraus, LLP
Bishop Steven C.
Danieli & C. Officine Mecchaniche SpA
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