Patent Grant
10870139
The present application is a 35 U.S.C. §§ 371 national phase conversion of PCT/EP2015/065731, filed Jul. 9, 2015, which claims priority of European Patent Application No. 14179980.9, filed Aug. 6, 2014, the contents of which are incorporated by reference herein. The PCT International Application was published in the German language.
The present invention relates to the field of metallurgical plants, specifically a rolling mill with a cooling zone for cooling down metal strips, preferably strips of steel, and shears for cutting the strips.
On the one hand, the invention relates to a method for cross-cutting a metal strip, preferably a steel strip, wherein the method comprises the following steps:
On the other hand, the invention relates to a facility for cross-cutting a metal strip for carrying out the inventive method. The facility includes a roller track for feeding the metal strip, with at least one cooling facility, wherein a cooling device is arranged before shears to be used for cross-cutting the metal strip, so that the metal strip is divided crosswise into a preceding or leading section of metal strip, having a strip tail of the preceding section of metal strip, and a following or trailing section of metal strip having a strip head of the following section of metal strip, and the strip head of the following section of metal strip follows on immediately in the direction of transport from and after the strip tail of the preceding section of metal strip.
In the following description, shears ahead of the finishing line, which may for example be in the form of pendulum shears, are referred to as a cutting facility. Shears, for example constructed in the form of drum shears, are arranged after the finishing line and before a coiler and are referred to as shears.
Cross-cutting of metal strips, especially of high-strength steel materials (with yield stresses above 500 MPa) and/or with thicknesses greater than 4 mm demands, under the prior art, some changes to the plant configuration. In order to be able to reliably cut high-strength and/or thick metal strips, the construction of some of the parts of the plant must be appropriately larger. Due to inertia and the high cutting speed, the shears before the coiler cannot be designed to be arbitrarily large. Because of these restrictions, the metal strip is often cut on a cutting facility which is located before the finishing line, and after this the metal strip is finish-rolled in batch mode. However, as a consequence of this, in order to ensure an adequate gap between the tail of a strip and the head of a strip the preceding section of any strip must be rapidly accelerated. An adequate gap is required in order that no collisions may occur between the strip head and the strip tail in subsequent parts of the plant e.g. before the coiler. Furthermore, it is necessary to ensure that it is impossible for two different metal strips to be simultaneously on the same section of the exit roller track. The gap may also be necessary if a change is planned to the roll gap, due to a change in the thickness in the following metal strip. The increase in speed also means that the subsequent parts of the plant, for example the induction furnace, finishing line and the cooling line will be passed through more rapidly.
When the strip passes through the finishing line, temperature rises also occur due to the greater speed, which has a negative effect on the mechanical properties of the strip and on its surface quality. So that the mechanical properties of the metal strip remain homogeneous over its length, the process parameters of the plant sections must be adjusted appropriately, in order to avoid disadvantageous temperature rises. The cooling pattern of the cooling zone must also be appropriately adjusted. The cutting at the shears prior to the finishing line has a particularly disadvantageous effect in the case of an ESP (Endless Strip Production) plant, because the advantages of the stable endless operation are thereby obviated.
WO/59650 discloses a plant with a continuous casting facility, a pre-rolling line, a cutting facility, a furnace, a coiling facility, a descaler, a finish-rolling line, a cooling facility, shears and yet another coiling facility. An intermediate strip is cross-cut at a cutting facility, wherein a preceding metal strip has a strip tail and a following metal strip has a strip head.
The strip tail which has already been cross-cut and the strip head which is also already physically present are then superheated in an induction furnace and are wound up by means of the coiling facility. After this, the metal strip is unwound again from the coil and is finish-rolled on a finishing line. Due to the superheated strip head and strip tail of the metal strip, this plant is especially suitable for rolling thin metal sheets of >1 mm. The superheating of the strip head and strip tail result in comparable qualities as are the case with cold-rolled metal strips. Shears are arranged after a cooling facility. The shears can cross-cut the thin hot-rolled metal strip to strip lengths.
EP0730916 A1 discloses a hot-rolling line, which has the following plant sections, a continuous casting facility, a furnace, a rolling line, shears and a coiling facility. On the hot-rolling line, one can change the thickness of the metal strip to be rolled during ongoing operation. A tracking device enables the change in the thickness of the metal strip to be detected, and the shears are actuated by this tracking device. When a change in thickness of the metal strip is detected, the shears are activated to make a cross-cut. In the coiling facility which follows, the metal strip is then finally coiled up again.
It is the object of this invention to provide a method and a facility of the type mentioned in the introduction, with which even metal strips with a thickness greater than 4 mm and/or metal strips made of high-strength materials (yield stresses over 500 MPa) can be cross-cut using shears which are arranged after a finish-rolling line and after a cooling line.
This object is achieved for the method mentioned in the introduction by cooling the metal strip in the cooling zone to a prescribed temperature profile in the longitudinal direction of the metal strip, so that in the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, the metal strip has a higher temperature than in the preceding and following regions.
To do this, the metal strip is fed in the direction of transport through a cooling zone. In the cooling zone, the metal strip is cooled down. After this, a cross-cut is made in the metal strip at the shears, so that the cross-cut metal strip has a strip head of the following section of metal strip and a strip tail of the preceding section of metal strip. The start of a metal strip, in the direction of transport, is referred to as the strip head. The strip tail of the preceding section of metal strip is the end of the preceding section of metal strip after cross-cutting. Thus, until the cross-cutting, the strip head of the following metal strip and the strip tail of the preceding metal strip are identical, and each only exists as an imaginary plane transverse to the direction of transport. The strip head of the following section of metal strip and the strip tail of the preceding section of metal strip are defined even before they enter into the cooling facility, and not merely after the cross cut has been made. The term ‘section of metal strip’ defines that part of the metal strip which is wound up into one coil. Hence, during production many individual sections of metal strip are created. Until the cross-cutting, the sections of metal strip are all part of a unitary metal strip. After the cross-cut has been made, and the advancing section of metal strip has been finally coiled up, what was previously the following section of metal strip becomes the leading section of metal strip for the next cross-cut. In the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip a temperature profile is set, by the cooling zone, which has a higher temperature than in the regions located before and after them.
By causing the higher temperature in the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, the yield stress in the region is reduced, preferably by up to 50%. For the highest strength steel varieties, the reduction in the yield stress can even be >50%. The cutting force which must be applied for cross-cutting the strip is thereby reduced correspondingly. Cross-cutting of the metal strip can be effected without problem using commonly used shears. It is thus possible to forgo making the shears larger which is anyway also only possible within a limited range due to inertia, and which in addition has high associated costs. Furthermore, it is also unnecessary to cut the metal strip using the cutting facility (i.e. before the finish-rolling line) and to design the subsequent parts of the plant to be larger, or to arrange after the finishing line additional second shears designed for cross-cutting the large thicknesses. This method ensures that the same plant can also cross-cut high strength metal strips and/or metal strips with a thickness >4 mm without having to accept any loss of quality in the strip characteristics and the surface quality.
In one advantageous embodiment of the method, the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip is tracked constantly (i.e. in real time), at least from the start of the cooling zone up to the shears. The strip head of the following section of metal strip and the strip tail of the preceding section of metal strip are already defined before the metal strip passes into the cooling zone. By the tracking of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, this region is constantly determined during its entire passage, from at least the start of the cooling zone up to the shears. This makes it possible to set selectively a temperature profile in the desired region of the later strip head and strip tail.
The temperature profile which is set on the metal strip is advantageously a ramp profile. This makes it possible to set an optimized temperature profile for each quality and/or thickness of steel in order to minimize the cutting force at the shears. However, it is also possible to make use of other temperature profiles, for example a step profile or a sine-shaped temperature profile.
Advantageously, the temperature in the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip is higher by at least 100° C. than that of the rest of the metal strip. Above this temperature difference, the forces which must be used for cross-cutting start to reduce significantly.
With one particularly preferred embodiment of the invention, the strip tail of the preceding section of metal strip and the strip head of the following section of metal strip are not cooled while the remaining regions of metal strip are cooled. This enables the forces to be applied in cross-cutting to be the most reduced.
The metal strips for which this method is particularly suitable are those consisting of high and maximum strength materials, especially pipe steels such as X70 or X80, hot strip multi-phase steels, for example dual phase steels DP600, DP800, DP1000, among others, or fully martensitic steels.
This method makes it possible to cross-cut even high-strength metal strips with a thickness >4 mm. For this purpose, the shears need not be larger in construction. Using the inventive method it is possible, with the same plant configuration, with shears of which standard use is made, to cross-cut without problem a metal strip made, for example, of DP1000 dual-phase steel with a thickness of 8 mm. Without the inventive method, only a maximum of 4 mm would be possible. It is of course also conceivable that use is made of smaller shears, with which, for example, a maximum thicknesses of 2.5 mm could be cross-cut. Using the inventive method it is possible, using the same shears, to cross-cut metal strips of 5 mm with no problem.
In order to produce the temperature profile on the metal strip, it is advantageous if this is effected by the amount of coolant fed in the cooling zone. The temperature profile is set in the cooling zone, in the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, in that in this region the coolant is either not applied at all or only to a reduced extent.
During the passage of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip through the cooling zone, the feed of the coolant is adjusted according to the desired temperature profile.
In a further expedient embodiment, the adjustment of the amount of coolant is effected discretely. In the case of a discrete setting of the amount, either 100% of the coolant is applied, or 0%. This has the advantage that the design of the cooling zone can be simple, with no requirement for expensive adjustment elements—e.g. for setting the amount. A design of a continuous nature is equally conceivable. In this case the setting is effected by means of the amount or the pressure.
This method is particularly advantageously suitable if the metal strip is rolled on a rolling line of a combined continuous casting/rolling plant before cooling in the cooling zone. This method can also be applied even in existing plants without major conversion measures. The application of this method is especially preferred for ESP (Endless Strip Production) plants. This brings the clear advantages that, with the same plant configuration, endless operation can also be extended to high-strength qualities and greater thicknesses without having to accept any disadvantageous implications for the strip characteristics.
A further advantageous embodiment of the method is that the metal strip is coiled up on a coiler after cross-cutting. Due to the higher temperature of the strip head of the following section of metal strip, the threading up on the coiler is made easier as is the subsequent winding on. At the same time, instances of damage such as dents in the driving rollers are avoided. The term coiler refers to the facility which coils up the metal strip.
A further advantageous embodiment is that the length of a partial piece of a metal strip which has a raised temperature is ≥ a circumference of one coil, so that the coil is hot-packed by the strip tail of the preceding section of metal strip. The raised temperature of the strip tail of the preceding section of metal strip has in addition the positive effect that the metal strip cools down more uniformly. Because the outermost layer cools down more quickly—than those lying beneath it the cooling down process is more uniform over the entire length of the coiled-up metal strip, which results in more homogeneous properties. The length of the hot strip tail should advantageously be at least equal to the circumference of the coil. The term coil refers to the metal strip which is wound up on the coiler to form a roll.
For cross-cutting the metal strip, one particularly advantageous implementation is that the blade gap of the shears be set as a function of the thickness of the metal strip. This makes it possible to optimize yet further the operation of cross-cutting, even during operation, and the cutting forces can be further reduced depending on the thickness of the metal strip. There is, to a first approximation, a linear relationship between the ideal blade gap and the thickness of the metal strip.
The object of the invention is also achieved by the facility mentioned in the introduction, which comprises the following:
Using this facility, it is possible to track continuously the position of the later strip head and strip tail of the metal strip, at least from the start of the cooling facility up to the shears, and to control the cooling facility according to the position of the later strip head of the following section of metal strip and the strip tail of the preceding section of metal strip.
By contrast with this, the document EP0730916 shows a tracking facility which detects a change in the strip thickness. Shears are then actuated by this tracking facility. However, a tracking facility from the start of the cooling facility up to where the shears are reached is not shown in this document. Nor is any actuation of the cooling facility by reference to the position of the strip head and strip tail shown. An embodiment of this type also cannot be deduced without a knowledge of the method disclosed above, and it is also not in any way obvious.
One advantageous embodiment of the cooling facility has at least three cooling sections, separate from one another, wherein the at least three cooling sections can be controlled or regulated separately from each other. Having at least three separate cooling sections ensures that the temperature profile can be reliably produced on the metal strip. When the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, which is to have a higher temperature, reaches the cooling line, the cooling section which is first in the direction of transport is switched off, while the other cooling sections remain switched on. When the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, which is to have a higher temperature, approaches a second cooling section, this too is switched off and, as soon as the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, which is to have a higher temperature, has left the first cooling section, this is switched on again. When the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, which is to have a higher temperature, approaches a third cooling section, this is switched off and, as soon as the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, which is to have a higher temperature—has left the second cooling section, this is switched on again. This takes place in an analogous way for all of the subsequent cooling sections of the cooling facility. Exactly when the particular cooling section is switched on or off depends on what temperature profile is to be produced on the metal strip, and how many cooling sections the cooling facility has. Above all, however, it is dependent on which region before the strip tail of the preceding section of metal strip and which region after the strip head of the following section of metal strip are to have a higher temperature.
In order to be able to ensure particularly exact tracking of the position of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip, it is advantageous if the tracking facility has a computing facility and at least one position or speed sensor, which control the cooling facility before the cross-cutting of the metal strip in such a way that the desired temperature profile is set in the region of the strip head of the following section of metal strip and of the strip tail of the preceding section of metal strip. The position or speed sensor can be a contact arrangement (e.g. pressing down of a roller or from the rotational speed at the coiler) or a non-contact arrangement (optically, for example using a laser).
With respect to the form of embodiment of the cooling facility, it is expedient to make the cooling facility as a water cooling line.
It is particularly advantageous if the cooling facility is constructed in such a way that in the direction of transport the amount of water flowing through the jets of the cooling facility can be controlled or regulated individually or in sections by a setting facility which is linked to the control facility. The water jets are mounted on spray bars. If one looks along the direction of transport at the individual spray bars, which extend across the direction of transport over the entire width of the metal strip, then each spray bar represents of itself the smallest section. On these spray bars there can be, e.g. little tubes or jets through which the water emerges. The sections can then, depending on the requirements which the metal strip concerned demands, be split up into any desired sizes. It is thus even possible to actuate several spray bars jointly. However, it is also conceivable that each jet on each spray bar is actuated individually.
In one advantageous embodiment, the tracking of the region of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip is implemented with a temperature measuring facility. In order to detect the strip tail of the preceding section of metal strip and the strip head of the following section of metal strip, use can again be made of temperature measurement facilities. The advantages which result from doing so are: to compare the temperature profile with the prescribed one, to determine the exact position of the strip head of the following section of metal strip and the strip tail of the preceding section of metal strip and to compare it with the calculated position. The temperature measurement facilities can be arranged in the most varied of positions. Here, advantageous positions are before the cooling zone, in the middle of the cooling zone, after the cooling zone and before the shears.
For cross-cutting the metal strip, one particularly advantageous embodiment is that the shears have a facility for adjusting the blade gap, wherein the then current thickness of the metal strip can be fed to the facility for adjusting the blade gap. By this means, the process of cross-cutting can be further optimized and the cutting forces further restricted, depending on the thickness of the metal strip.
Setting of the blade gap is effected according to the thickness of the metal strip. The thicker is the metal strip which to be cross-cut, the larger is the blade gap made.
Further advantages and features of the present invention are revealed from the description which follows of exemplary embodiments, not restrictive, wherein reference is made to the figures below, which show the following:
| Number | Date | Country | Kind |
|---|---|---|---|
| 14179980 | Aug 2014 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/065731 | 7/9/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2016/020134 | 2/11/2016 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5560236 | Onda | Oct 1996 | A |
| 5727412 | Tippins | Mar 1998 | A |
| 6536254 | Kawalla | Mar 2003 | B1 |
| 8282747 | Oda | Oct 2012 | B2 |
| 8359119 | Schmors | Jan 2013 | B2 |
| 8601851 | Seidel | Dec 2013 | B2 |
| 9174255 | Diez et al. | Nov 2015 | B2 |
| 9889480 | Nelson | Feb 2018 | B2 |
| 20020184984 | Rosenthal | Dec 2002 | A1 |
| 20040221929 | Hebda | Nov 2004 | A1 |
| 20100132426 | Baumgartel | Jun 2010 | A1 |
| 20100175452 | Ohlert | Jul 2010 | A1 |
| 20100180655 | Ishige | Jul 2010 | A1 |
| 20120004757 | Imanari | Jan 2012 | A1 |
| 20120103052 | Ueoka | May 2012 | A1 |
| 20120160377 | Seidel | Jun 2012 | A1 |
| 20130145807 | Benedetti | Jun 2013 | A1 |
| 20140034264 | Benedetti | Feb 2014 | A1 |
| 20140096578 | Eckerstorfer | Apr 2014 | A1 |
| 20150023387 | Narihara | Jan 2015 | A1 |
| 20150196941 | Lengauer | Jul 2015 | A1 |
| 20150218668 | Kwak | Aug 2015 | A1 |
| 20150306645 | Song | Oct 2015 | A1 |
| 20150375286 | Jirkova | Dec 2015 | A1 |
| 20160067753 | Klein | Mar 2016 | A1 |
| 20160101450 | Linzer | Apr 2016 | A1 |
| 20160243611 | Benedetti | Aug 2016 | A1 |
| 20170209907 | Kuegel et al. | Jul 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 101378856 | Mar 2009 | CN |
| 101755058 | Jun 2010 | CN |
| 694 10 562 | Oct 1998 | DE |
| 10 2007 007 560 | Aug 2008 | DE |
| 10 2008 010 062 | Dec 2008 | DE |
| 0 730 916 | Sep 1996 | EP |
| 1 925 373 | Aug 2008 | EP |
| 2 258 491 | Dec 2010 | EP |
| 3 177 412 | Jun 2017 | EP |
| 62234611 | Oct 1987 | JP |
| S62234611 | Oct 1987 | JP |
| 10-29004 | Feb 1998 | JP |
| 2003-200203 | Jul 2003 | JP |
| 2415725 | Apr 2011 | RU |
| WO 0059650 | Oct 2000 | WO |
| Entry |
|---|
| Machine translation of JP-62234611-A, Tagashira, pp. 1-3, translated on Apr. 30, 2019. (Year: 2019). |
| English translate (JPS62234611A), retrieved date Nov. 22, 2019. |
| Temperature and Strength of Metals, retrieved date Nov. 22, 2019. |
| EngArc—L—Effect of Temperature on Tensile Properties, retrieved date Nov. 22, 2019. |
| M. Spittel et al. “Numerical Data and Functional Relationships in Science and Technology” New Series / Editor in Chief: W. Martienssen, Flow stress of steel, pp. 1-33 (2009). |
| International Search Report dated Sep. 24, 2015 issued in corresponding International patent application No. PCT/EP2015/065731. |
| Written Opinion dated Sep. 24, 2015 issued in corresponding International patent application No. PCT/EP2015/065731. |
| European Search Report dated Dec. 19, 2014 issued in corresponding European patent application No. 14179980.9. |
| Russian Federation Decision to Grant, dated Dec. 12, 2018, issued in corresponding Russian Federation Patent Application No. 2017106342/04(011160). Total 12 pages. |
| Office Action dated Dec. 7, 2018 issued in corresponding Chinese Patent Application No. 201580042202.5 with English translation. |
| Indian First Examination Report issued in Indian Application No. 201717002528 dated May 23, 2019. |
| European Notice of Opposition issued in European Patent Application No. 15738039.5 dated Jun. 24, 2019. |
| Engel et al., “Hochfeste Stähle,” IBU Vortragsreihe; Universität Siegen (Dec. 2008) and Statement of Relevance. |
| Number | Date | Country | |
|---|---|---|---|
| 20170209907 A1 | Jul 2017 | US |
