Metal deforming – With cleaning – descaling – or lubrication of work or product
Reexamination Certificate
2001-04-23
2002-09-24
Tolan, Ed (Department: 3725)
Metal deforming
With cleaning, descaling, or lubrication of work or product
C072S203000, C072S365200
Reexamination Certificate
active
06453709
ABSTRACT:
The invention relates to a cold-rolling method and installation for a metal band, especially suited for an average yearly production, for example ranging between 300,000 and one million tons.
The invention applies in particular to descaling and rolling steel sheets and strips obtained by hot rolling or by thin continuous casting.
It is known that generally, the manufacture of metal products calls, first of all, for the preparation of a raw product by ingot mould casting or continuous casting, hot transformation by forging and/or hot rolling and cold transformation comprising various steps that depend on the nature of the metal, for example ferritic or austenitic steel, and on the product to be manufactured, for instance ordinary steel, stainless steel, alloyed steel.
Usually, the hot prepared product is subject, successively, to a descaling treatment for descaling, to cold rolling until the requested thickness is obtained and, possibly, to finishing treatments that depend on the type of sheet to be produced, for example annealed, galvanised or other surface treatment.
Cold rolling is conducted, normally, in several successive passes, either in two opposite directions on a reversible mill, or on several rolling stands operating in tandem.
Up to recently, the various cold treatments had always been carried out in a discontinuous fashion in different installations, whereas the product is wrapped into a coil at the end of each step in order to be transferred to the next step. These non-continuous methods therefore require several unwinding and winding operations of coils as well as intermediate storing phases generating significant costs, taking into account the necessary handling tools and staff.
Moreover, in reversible rolling, a minimum band length must remain wound on each coil and is therefore not rolled. These parts outside tolerances cannot be marketed and must hence be eliminated.
To remedy these shortcomings, the last few years have seen the development of continuous line manufacturing methods that enable doing away with coil winding at least for certain intermediate steps. In particular, we already know methods in which certain cold transformation operations are carried out continuously on a single line. For example, coupling pickling with cold rolling enables reducing, to a vast extent, the shortcomings stated above.
A coupled line installation of this type comprises, generally, an inlet section containing a device for unwinding, one after the other, coils to be treated, a pickling section for descaling, generally by immersing the band in a chemical pickling liquid, a cold rolling section and an outlet section comprising means for winding the rolled band into a coil.
To perform continuous running of the band, the inlet section comprises linking means, by welding or stapling, of the downstream extremity, in the running direction, of a first coil with the upstream extremity of the following coil. Thus, we obtain a continuous band running successively through the different sections of the line.
In normal operation, a same running speed, for example 400 m/min or even more, is maintained up to the inlet of the mill and increases then in relation to the reduction in thickness.
However, for various reasons, it is necessary to vary considerably the speed of a section with respect to the adjacent sections, respectively upstream and downstream.
For example, during the time necessary to the connection of extremities of two successive coils, the inlet section is stopped, whereas the band must still be running in the pickling section whose stoppage might cause defects on the metal further to an excessive dwelling in the acid used.
Similarly, it is required, in some cases, to stop or, at least, to slow down the running in the rolling mills, for example for maintenance operations. Indeed, the working rolls are worn quite rapidly and must be replaced periodically with new rolls. During the time necessary to replacement, the rolls are held away from the band and, even if the running of the band is not stopped completely, it should be at least slowed down in order to reduce the length of the band that has not been rolled, which then should be eliminated.
On the other hand, after rolling, the band is wound once more in order to form a coil and, when the said band reaches its maximum length, the band must be shorn to allow evacuation of the wound coil. To avoid complete stoppage of the band during shearing, it is advantageous to use so-called ‘flying’ shears composed of two blades mounted respectively on two rotating drums, but the speed must, however be reduced.
After shearing, the band must be wound to the end and the complete coil must be evacuated, then the shorn extremity of the following band must be attached to the reeling plant in order to constitute a new coil
To do so, two coilers operating alternately may be used, with a switching system that enables, after shearing, to direct the upstream extremity of the following band immediately to the second coiler for winding the new coil, whereas retraction of the wound coil on the first coiler is performed in hidden time. A so-called carousel coiler comprising two winding mandrels operating alternately can also be used.
These arrangements enable reducing the time necessary to changing the coil, but the shorn band should run forward at low enough speed to enable its extremity to engage on the chuck and to start the winding process.
It seems therefore that even if perfected arrangements enable to reduce the time necessary to certain operating phases during which the running speeds in the different sections of the line must vary independently from one another, it is necessary to place means for accumulating the band between certain sections. Thus, the band can be accumulated at the outlet of a section when the running is stopped or slowed down downstream and, conversely, when the running is stopped or slowed down in a section, it is possible to continue running, downstream, a band length accumulated previously.
Generally, such a coupled line must comprise at least two means of accumulation placed, respectively, at the inlet and at the outlet of the handling section. Thus, before reaching the end of a coil, a certain length of the band will be accumulated, which will continue to run in the handling section for the time necessary to the connection with the extremity of the following coil. Similarly, if the mill has been stopped, for example for replacing the rolls, the band should be run further in the pickling tanks, while accumulating the pickled length at the outlet of the treatment section.
Obviously, other members are necessary such as tensioning devices for traction load adjustments in the different sections or edge shears.
All these members are obviously quite expensive and call for high energy expenses and maintenance costs.
Indeed, to ensure the necessary high running speeds, the control motors of the various pieces of equipment must be very powerful.
Moreover, after usage, the inlet accumulator of the treatment section must be emptied in order to compensate for later speed variations.
Still, these operations must be carried out very rapidly in order to reduce the transition periods and require therefore motors capable of supplying the necessary accelerations.
Besides, in order to maximise the operation of the mill, the said mill must be suited to certain types of products and the other sections of the line, in particular pickling and finishing sections, must be provided accordingly.
Therefore, although such installations are extremely costly, their operating conditions must paradoxically be sufficiently rigid to ensure profitable production with the quality requested.
Because of the investment costs, the energy expenses and the maintenance costs, such coupled installations had been provided so far only for high production levels, ranging for example between 1 and 2 million tons per annum, if not more. Such capacities are, obviously, justified only for certain types of products and, in other cases, it seems more economical to use co
Leroux Francois
Valence Marc
Arent Fox Kintner Plotkin & Kahn
Tolan Ed
Vai Clecim
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