Patent Application
20100077823
The invention relates to the general field of thermo-mechanical controlled rolling of metal slabs to plates or strips in a rolling mill, in particular to a technique known as interleaving and an apparatus for performing that technique.
Thermo-mechanical controlled rolling involves the rolling of metal-slabs, plates or strips at specific temperatures in order to achieve specific metallurgical microstructures and mechanical properties. It typically involves two or more rolling phases. Between two successive rolling phases the plates or strips are allowed to cool down during a cooling phase to the specific temperature which is desired for the next rolling phase. For example, when two rolling phases are performed first a number of passes are rolled at a high temperature during the first rolling phase, and then the obtained plate or strip is allowed to cool down to a specific temperature in a cooling phase before the second rolling phase starts. Analogously, in three phase rolling two cooling phases take place, a first one between rolling phase 1 and rolling phase 2, and a second one between rolling phase 2 and rolling phase 3.
To increase a thermo-mechanical controlled rolling mill's throughput the interleaving technique is employed. It consists in concurrently processing more than one metal slab, plate or strip in the rolling mill.
When no interleaving technique is employed in thermo-mechanical controlled rolling, the rolling of a plate or strip has to be completed, i.e. the plate or strip has to have passed all rolling phases, before rolling of another, new slab can start. While a plate or strip cools down between two rolling phases during a cooling phase the rolling mill is completely idle. Contrary to that, according to the interleaving technique rolling of new slabs already starts while a plate or strip previously subjected to rolling phase 1 cools down during a cooling phase. Thereby, the rolling mill is not always completely idle during the cooling phases of one plate or strip since it is processing other plates or strips meanwhile. Hence, the rolling mill's throughput is considerably enhanced by application of the interleaving technique. The interleave depth is a characteristic parameter for thermo-mechanical controlled rolling according to interleaving technique. In order to obtain a special product by thermo-mechanical rolling via interleaving technique, a special rolling pattern is applied on each slab of the batch to be processed. The rolling pattern is the sequence and duration of all rolling phases and cooling phases which are applied when processing a slab to a plate or strip. Such a rolling pattern comprises at least two rolling phases, and cooling phases between successive rolling phases. For rolling patterns with unequal durations of the rolling phases interleave depth is defined as the integer number obtained by rounding the smallest value from the group of values consisting of the quotients of the durations of the cooling phases and the duration of the longest rolling phase down to a whole number. For rolling patterns with equal durations of the rolling phases interleave depth is defined as the integer number of the obtained by rounding the smallest value from the group of values consisting of the quotients of the durations of the cooling phases and the duration of a rolling phase down to a whole number.
For example, in a group of values consisting of 2.30, 1.98 and 1.95 the smallest value is 1.95. 1.95 rounded down to a whole number is 1. Hence, the interleave depth is 1. If the smallest value is a whole number the integer number defining the interleave depth is equal to that whole number.
For example, for two phase rolling with equal durations of the rolling phases the interleave depth is defined as the integer number which is the quotient of the duration of the cooling phase and the duration of a rolling phase rounded down to a whole number.
In the most common method for interleaving the plates or strips are stored during their cooling phases on the same roller tables that are used for rolling.
Such a technique is illustrated in
Then a second slab is discharged from the furnace 1 and rolled in the same way as the first slab until its rolling phase 1 is completed. The thereby obtained plate 7 is then moved down the roller table 4 to a storage position 8 where plate 7 is stored during its cooling phase.
Then a third slab is discharged from the furnace 1 and rolled until its rolling phase 1 is completed to yield plate 9.
Then all three plates are transported by the roller tables 4 and 2 back to the entry side of rolling mill stand 3 and rolling phase 2 with a number of reversing rolling passes starts for plate 5.
A disadvantage of storing plates during their cooling phases on the same roller tables that are used for rolling is the additional length of the roller tables, and of the building housing the roller tables, that is required in comparison to thermo-mechanical rolling without interleaving technique. In the example illustrated in
Modern plate grades often require very long cooling times, hence interleave depth can be up to twelve or even more. In analogy with the example shown in
A solution to store plates during their cooling phases in a shorter overall length of a rolling mill is shown in GB1396946 which discloses side-shift roller table sections which can be moved transversely out of the rolling line. At the start of a cooling phase a plate is positioned on one of the side-shift roller tables and then moved transversely off-line into a storage position. This transverse movement of the side-shift roller table either brings a cooled plate ready for the next rolling phase into the rolling line or it brings an empty side-shift roller table back into the rolling line. Since the plates are not stored in a row but side by side, the required length of roller tables and building is significantly reduced. However, to cope with an interleave depth of twelve would require twelve side-shifting roller tables which would take up a very large transverse area that would not fit into a standard rolling mill building.
Another known solution to the problem of storing large numbers of plates during their cooling phases is to use one or more storing roller tables which run parallel with the mill line roller tables and moving-equipment to move plates between the mill line and the holding line. After rolling phase 1 is finished a moving-equipment moves the plates onto the storing roller tables. When the cooling period is finished the plate is moved back into the mill line for rolling phase 2.
However, to handle an interleave depth of twelve according to the example described above, a storing roller table parallel to the mill-line roller table would still need to be around 120 metres long. To use two or more storing tables with moving-equipment in order to shorten the required length of each individual additional table would increase the complexity of the equipment and need more transverse space.
Another known solution to the he problem of storing large numbers of plates during their cooling phases is to lift the plates up above the mill line roller table. This works similarly to the use of the side-shift roller tables, except that the movement is vertical instead of horizontal. Again, to handle large interleave depths would increase the complexity of the necessary equipment as well as the dimensions of rolling mill's housing.
Another disadvantage of the interleaving methods of the prior art is that their furnace discharge pattern of slabs is not ideal.
The processed batch contains 6 slabs which yield plates 1-6. According to the rolling pattern in
The discharge of a large group of slabs at short intervals followed by a long gap causes problems with the slab temperature control and the furnace temperature control. Due to an irregular, uneven furnace discharge pattern some slabs will stay longer in the furnace than others, uneven staying times causing different temperatures for different slabs and thereby affecting metallurgy and yield negatively.
The object of the present invention is to provide a method and an apparatus for thermo-mechanical controlled rolling by interleaving technique which permit the application of a more even furnace discharge pattern and require less space and equipment than the prior art.
This object is solved by a method for thermo-mechanical controlled rolling a batch of metal slabs to plates or strips on a rolling mill comprising at least one rolling mill stand according to a rolling pattern comprising at least two rolling phases of at least one rolling pass and cooling phases between successive rolling phases, which rolling pattern is applied on each slab of the batch, characterized in that, during rolling the batch, on at least one rolling mill stand it occurs several times that a rolling phase applied to one slab or plate or strip is succeeded by a different rolling phase applied on another slab or plate or strip, and that for two successively rolled slabs the time gap between the starts of their rolling phases 1 is always smaller than the sum of the duration of all rolling phases and all cooling phases of the rolling pattern.
This method permits the application of a furnace discharge pattern that is more even than in the prior art. As can be seen in
Preferably, after the first rolling phase of the first slab of the batch has been completed until the beginning of the last rolling phase of the last plate or strip there is always at least one other plate or strip in its cooling phase.
More preferably, this is the case for batches larger than interleave depth plus one, the interleave depth of the method's rolling pattern,
being defined
for rolling patterns with unequal durations of the rolling phases as the integer number obtained by rounding the smallest value from the group of values consisting of the quotients of the durations of the cooling phases and the duration of the longest rolling phase down to a whole number, and
for rolling patterns with equal durations of the rolling phases as the integer number obtained by rounding the smallest value from the group of values consisting of the quotients of the durations of the cooling phases and the duration of a rolling phase down to a whole number.
In an embodiment of the invention the number of rolling phases is two, namely rolling phase 1 and rolling phase 2, which are separated by one cooling phase.
It is preferred for two-phase thermo-mechanical controlled rolling methods with rolling patterns with an even numbered interleave depth and equal durations of the rolling phases where the duration of the cooling phase is equal to the sum of
that for successively rolled slabs the maximum time gap between the starts of their rolling phases 1 is up to the sum of twice the duration of one rolling phase and the remainder time. In this case the whole number is the integer of the quotient of cooling phase duration and duration of one rolling phase.
Expressed in mathematical terms this is:
Tg≦(2·Drp)+Rt
Cpd=(Wn·Drp)+Rt
By limiting the maximum time gap between the starts of the rolling phases 1 of successively rolled slabs to this value a more even furnace discharge pattern becomes possible.
It is preferred for two-phase thermo-mechanical controlled rolling methods with rolling patterns with an even numbered interleave depth and unequal durations of the rolling phases, where the duration of the cooling phase is equal to the sum of
that for successively rolled slabs the maximum time gap between the starts of their rolling phases 1 is up to the sum of twice the duration of the longest rolling phase and the remainder time. In this case the whole number is the integer of the quotient of cooling phase duration and duration of the longest rolling phase.
Expressed in mathematical terms this is:
Tg≦(2·Dlp)+Rt
Cpd=(Wn·Dlp)+Rt
By limiting the maximum time gap between the starts of the rolling phases 1 of successively rolled slabs to this value a more even furnace discharge pattern becomes possible.
It is preferred for two-phase thermo-mechanical controlled rolling methods with rolling patterns with an uneven numbered interleave depth and equal durations of the rolling phases, where the duration of the cooling phase is equal to the sum of
that for successively rolled slabs the maximum time gap between the starts of their rolling phases 1 is up to the sum of thrice the duration of one rolling phase and the remainder time. In this case the whole number is the integer of the quotient of cooling phase duration and duration of one rolling phase.
Expressed in mathematical terms this is:
Tg≦(3·Drp)+Rt
Cpd=(Wn·Drp)+Rt
By limiting the maximum time gap between the starts of the rolling phases 1 of successively rolled slabs to this value a more even furnace discharge pattern becomes possible.
It is preferred for two-phase thermo-mechanical controlled rolling methods with rolling patterns with an uneven numbered interleave depth and unequal durations of the rolling phases, where the duration of the cooling phase is equal to the sum of
that for successively rolled slabs the maximum time gap between the starts of their rolling phases 1 is up to the sum of thrice the duration of the longest rolling phase and the remainder time. In this case the whole number is the integer of the quotient of cooling phase duration and duration of the longest rolling phase.
Expressed in mathematical terms this is:
Tg≦(3·Dlp)+Rt
Cpd=(Wn·Dlp)+Rt
By limiting the maximum time gap between the starts of the rolling phases 1 of successively rolled slabs to this value a more even furnace discharge pattern becomes possible.
It is preferred for two-phase thermo-mechanical controlled rolling methods with rolling patterns with equal durations of the rolling phases, where the duration of the cooling phase is equal to the sum of
that after completion of rolling the first plate or strip of the batch rolling phase 1 alternates with rolling phase 2 during rolling the batch at an interval which is up to the sum of interleave depth times duration of a rolling phase and the remainder time.
In this case the whole number is the integer of the quotient of cooling phase duration and duration of one rolling phase.
Expressed in mathematical terms this is:
Int≦(Id·Drp)+Rt
Cpd=(Wn·Drp)+Rt
For two-phase thermo-mechanical controlled rolling methods with rolling patterns with unequal durations of the rolling phases, where the duration of the cooling phase is equal to the sum of
it is preferred that after completion of rolling the first plate or strip of the batch rolling phase 1 alternates with rolling phase 2 during rolling the batch at an interval which is up to the sum of interleave depth times duration of the longest rolling phase and the remainder time.
In this case the whole number is the integer of the quotient of cooling phase duration and duration of the longest rolling phase.
Expressed in mathematical terms this is:
Int≦(Id·Dlp)+Rt
Cpd=(Wn·Drp)+Rt
For two-phase thermo-mechanical controlled rolling methods with rolling patterns with unequal durations of the rolling phases and a duration of the cooling phase that is equal to or longer than the sum of the durations of both rolling phases, or a whole number times that sum,
it is preferred that, after completion of rolling the first plate or strip of the batch, during a period of time equal to the duration of the cooling phase rolling phase 1 is performed as often as rolling phase 2.
In this case the whole number is the integer of the quotient of cooling phase duration and the sum of the durations of both rolling phases, i.e. in mathematical terms
For two-phase thermo-mechanical controlled rolling methods with rolling patterns with unequal durations of the rolling phases and a duration of the cooling phase that is equal to or longer than the sum of
or a whole number times that sum,
it is preferred that during the duration of the cooling phase the amount of rolling phases 1 performed is equal to the amount of rolling phases 2 performed plus 1 or minus 1.
In this case the whole number is the integer of the quotient of cooling phase duration and the sum of the durations of both rolling phases and the duration of either rolling phase 1 or rolling phase 2, i.e. in mathematical terms
In another embodiment of the invention the number of rolling phases is three, namely rolling phase 1, rolling phase 2 and rolling phase 3, rolling phase 1 and rolling phase 2 being separated by cooling phase 1, and rolling phase 2 and rolling phase 3 being separated by cooling phase 2.
It is preferred for three-phase thermo-mechanical controlled rolling methods with rolling patterns where the duration of cooling phase 1 is equal to the sum of
and where the duration of cooling phase 2 is equal to the sum of
that for successively rolled slabs the maximum time gap between the starts of their rolling phases 1 is up to the sum of the durations of the three rolling phases plus the greater of remainder time 1 and remainder time 2.
In this case the whole number A is the integer of the quotient of the duration of cooling phase 1 and the sum of the durations of all three rolling phases, and the whole number B is the integer of the quotient of the duration of cooling phase 2 and the sum of the durations of all three rolling phases.
Expressed in mathematical terms this is:
Tg≦Sdr+(the greater of Rt1 and Rt2)
Cpd1=(WnA·Sdr)+Rt1
Cpd2=(WnB·Sdr)+Rt2
By limiting the maximum time gap between the starts of the rolling phases 1 of successively rolled slabs to this value a more even furnace discharge pattern becomes possible.
It is preferred for three-phase thermo-mechanical controlled rolling methods with rolling patterns where the duration of cooling phase 1 is equal to the sum of
and where the duration of cooling phase 2 is equal to the sum of
that for successively rolled slabs the maximum time gap between the starts of their rolling phases 1 is up to the sum of the three rolling phase times plus the greater of remainder time 3 and remainder time 4.
In this case the whole number C is the integer of the quotient of the duration of cooling phase 1 and the sum of the durations of all three rolling phase plus the duration of rolling phase 3, and the whole number D is the integer of the quotient of the duration of cooling phase 2 and the sum of the durations of all three rolling phases plus the duration of rolling phase 1.
Expressed in mathematical terms this is:
Tg≦Sdr+(the greater of Rt1 and Rt2)
Cpd1=(WnC·(Sdr+Drp3))+Rt3
Cpd2=(WnD·(Sdr+Drp1))+Rt4
By limiting the maximum time gap between the starts of the rolling phases 1 of successively rolled slabs to this value a more even furnace discharge pattern becomes possible.
It is preferred for three-phase thermo-mechanical controlled rolling methods that during rolling the batch, from after completion of rolling the first plate or strip of the batch until the beginning of rolling phase 3 of the last plate or strip of the batch,
a rolling phase 1 is always succeeded by a rolling phase 2, and a rolling phase 2 is always succeeded by a rolling phase 3, and a rolling phase 3 is always succeeded by a rolling phase 1.
This pattern makes a very even furnace discharge pattern possible.
It is also preferred for three-phase thermo-mechanical controlled rolling methods that during rolling the batch, from after completion of rolling the first plate or strip of the batch until the beginning of rolling phase 3 of the last plate or strip of the batch,
a rolling phase 1 is always succeeded by a rolling phase 3, and a rolling phase 3 is always succeeded by a rolling phase 2, and a rolling phase 2 is always succeeded by a rolling phase 1.
This pattern makes a very even furnace discharge pattern possible.
It is preferred for three-phase thermo-mechanical controlled rolling methods that during a period of time equal to the duration of a cooling phase 1
rolling phase 1, rolling phase 2 and rolling phase 3 are performed equally often.
In another preferred embodiment of three-phase thermo-mechanical controlled rolling methods during a period of time equal to the duration of a cooling phase 1 rolling phase 1, rolling phase 2 and rolling phase 3 are performed unequally often. More preferably, during a period of time equal to the duration of a cooling phase 1 the number of rolling phases 3 performed is greater than the number of rolling phases 1 performed and greater than the number of rolling phases 2 performed,
and during a period of time equal to the duration of cooling phase 2 the number of rolling phases 1 performed is greater than the number of rolling phases 2 performed and greater than the number of rolling phases 3 performed.
It is further preferred that after completion of a rolling phase which is succeeded by a cooling phase the resulting plates or strips are transferred from a rolling line of the rolling mill to a storage position outside the rolling line by at least one moving-equipment, and afterwards are transferred from the storage position to the rolling line after completion of the cooling phase by the moving equipment.
Since thereby the plates or strips do not remain on the rolling line during their cooling phases, the length of the rolling line required for performing the interleaving method is reduced.
In an especially preferred embodiment, during rolling the batch it occurs at least once that while one plate or strip is transferred to its storage position or to the rolling line another plate or strip is simultaneously transferred to the rolling line or to its storage position by the same moving-equipment.
In this case two plates or strips are transferred by one movement of the moving-equipment. Thereby, the required number of movements of the moving-equipment during rolling the batch is reduced, which results in less need for supervision as well as less wearing down. In addition, less moving-equipment is needed.
The object of the invention is further solved by an apparatus for thermo-mechanical controlled rolling according to a method as claimed in claims 1 to 22,
comprising at least one rolling mill stand, a rolling line, storage positions outside the rolling line, and at least one moving-equipment for moving plates or strips from the rolling line to the storage positions, characterized in that the number of storage positions is half of the interleave depth of the performed rolling pattern rounded up to a whole number.
Compared to the prior art, where the number of storage positions required for the rolling pattern of an interleaving method is equal to the interleave depth of the rolling pattern, according to the present invention less storage positions are necessary. This results in diminished need for space and maintenance and in a less complex apparatus for thermo-mechanical controlled rolling.
The moving-equipment may be for example a side-shift roller table, lifting roller tables or cranes. The storage positions may be situated for example on one or more side-shift roller tables, lifting roller tables, or storing roller tables which may be parallel to the rolling line. In case of several parallel storing roller tables these may be staggered.
In a preferred embodiment at least one moving-equipment can simultaneously transfer one plate or strip to the rolling line or to a storage position and another plate or strip to a storage position or the rolling line.
This is for example the case for side-shift roller tables, which allow to transfer one plate or strip into the rolling line while simultaneously moving another plate or strip to a storage position.
The invention will now be described solely by way of example and with reference to the accompanying drawings in which:
After that, side-shift roller table 11 is moved into its up position, thereby removing plate 13 from the rolling line and transferring it into its storage position.
If the batch of metal slabs to be processed is larger than 4, another slab will start its rolling phase 1 when plate 13 clears the rolling mill, effectively repeating the situation which is shown in
In the example with an interleave depth of four outlined in
According to
In addition the invention as outlined in
In addition the invention as outlined in
Hence, the advantage of the present invention is that compared to the prior art it provides a possibility to use more even furnace discharge patterns, to reduce the number of storage positions needed, and to reduce the number of movements of the moving-equipment which transfers plates from the rolling line to storage positions and back.
While
An inventive two phase rolling pattern with an interleave depth of 3 and rolling phases of equal length is illustrated in the timing diagram of
Another advantage of the invention is illustrated by
In practice operation of the rolling mill without pause cannot be achieved because the cooling time is not necessarily an exact multiple of the duration of the rolling phases and some time is required to move the plates to and fro their storage positions.
A similar improvement in throughput is illustrated by
In
| Number | Date | Country | Kind |
|---|---|---|---|
| 07270012 | Feb 2007 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2008/000976 | 2/8/2008 | WO | 00 | 8/31/2009 |
