Patent Application
20220241833
The present invention relates to the field of rolling mill technology, in particular to hot-rolling and cooling a metallic strip, for example a steel strip, or a sheet in a rolling train. The rolling train can be, for example, a finishing rolling train for the production of strip, or a hot-rolling train for the production of sheet
The invention relates on the one hand to a roll stand having an operator-side roller housing and a drive-side roller housing, wherein no working rollers and no chocks for the working rollers are disposed in the roll stand.
The invention relates on the other hand to a method for installing a stand cooler for cooling a steel strip in a roll stand, as well as to a method for uninstalling a stand cooler of this type from a roll stand.
For reasons of clarity, a roll stand having uninstalled chocks and uninstalled working rollers is also referred to as a roll stand in this document. This nomenclature is self-evident to the person skilled in the art and enhances the clarity.
As is known, in hot-rolling the hot rolling stock is plastically deformed in a roll gap by so-called working rollers, which reduce the thickness of the rolling stock After hot-rolling, the rolled rolling stock is typically cooled in a cooling train and subsequently conveyed away from the rolling train, for example as a strip or sheet.
The material properties of a hot-rolled strip do not only depend on the chemical composition of the strip but also depend very heavily on the temporal sequence of the processing steps in the hot-rolling mill. In the case of a casting/rolling composite plant, for example an Arvedi ESP (Endless Strip Production plant, the temporal sequence of continuous casting, pre-rolling, intermediate heating, finishing rolling, cooling, and coiling is of substantial importance, for example. When setting the microstructure, or the phase fractions, respectively, of the rolled strip (the hot-rolled strip after finishing rolling is referred to as the finished strip), the temporal interval between the last rolling pass in a roll stand of the rolling train and the start of the cooling of the strip is also significant. This temporal duration should be as short as possible in many cases.
Hot-rolling mills have a fixed number of roll stands so that it is not possible by virtue of the high technical complexity of the machine for one or a plurality of roll stands of the rolling mill to be removed in the production of thick strips, and for removed roll stands to be added again in the production of thin strips. A rolling mill in general therefore has to be suitable for the production of thick strips as well as for the production of thin strips.
It is known that thick strips in a rolling mill are transported more slowly and the thickness of thick strips is reduced to a lesser extent than of thin strips. For example, this often leads to a thick strip being rolled to its final thickness already before passing the last roll stand, for example in the second roll stand, whereas a thin strip in the same rolling mill is rolled to its final thickness only in the last roll stand, for example the fifth roll stand. In the first-mentioned case, the roll stands 3, 4, and 5 are thus opened up such that the thick strip runs through the roll stands without being rolled therein. However, on account of the relatively slow transportation speed of thick strips and the fact that the last forming of the thick strip already takes place in one of the first roll stands, this causes a relatively long temporal duration until the finished strip reaches the cooling section following the last roll stand and therein is cooled by a specific intensity. This long temporal duration can lead to thick strips no longer being able to achieve specific material properties. On account of this, the product mix of the rolling mill is restricted.
This problem is further exacerbated in the continuous operation of casting/rolling composite plants since the transportation speed of the strip and the strip thickness are indirectly proportional. On account of the continuous operation the intermediate strip or finished strip cannot be accelerated on the roller table since the strip is coupled to the continuous casting plant. This leads to the transportation speed of a thick strip in an ESP plant potentially being in the range of 0.5 m/s or less, and of thus being substantially slower than in the case of other hot-rolling mills that are not operated in a continuous manner and can accelerate the rolling stock before, when, or after running through the rolling train, respectively.
However, the underlying problem cannot be satisfactorily solved even in the case of discontinuous operation (for example in the batch operation or the semi-continuous operation) of a hot-rolling mill, since variation in the strip speed is at all times also associated with variation in the temperature at the last rolling pass in the finishing rolling train. Moreover, cancellation of the endless coupling between apparatuses of a hot-rolling mill leads to many well-known problems, for example, the threading of the strip in and out of the roll stands and the cooling section, the shocks on account of the strip head and the strip base, the dissimilar temperatures of the strip head and the strip base, etc. This potential solution is thus also either completely excluded or is at least not implementable in a satisfactory manner.
A cooling assembly which can be disposed ahead of or behind a roll stand is known from US 2017/0 056 944 A1. This cooling assembly has a design embodiment such as, in terms of the basic approach, is known in conventional cooling sections. However, said cooling assembly by a few meters is shorter than conventional cooling sections.
An intermediate stand cooling for cooling a steel strip after a roll stand is known from DE 37 04 599 A1. The intermediate stand cooling comprises a lower and an upper water tank, wherein the water tanks in each case have one connector for a coolant, and a plurality of cooling nozzles or cooling pipes that are disposed in the depth direction of the stand cooler. The water tanks by way of the connectors can be supplied with coolant. This enables the lower side and the upper side of the steel strip to be cooled by cooling nozzles or cooling pipes of the water tanks.
Intermediate stand cooling is likewise known from DE 22 35 063 A1. Intermediate stand cooling comprises a lower and an upper water tank, wherein the water tanks have in each case one connector for a coolant and one cooling slot that extends in the depth direction. The water tanks can be supplied with coolant by the connectors. As a result, the lower side and the upper side of the steel strip can be cooled by way of the cooling slots of the water tanks.
In the case of thick strips, it cannot be derived from the prior art how the problem of the long temporal duration between the last rolling pass and the beginning of the cooling in hot-rolling mills, in particular in the case of continuously operated casting/rolling composite plants, can be overcome.
The object of the invention lies in modifying the current prior art by an innovative solution for a hot-rolling mill, in particular a casting/rolling composite plant, and here very particularly for a continuously operated casting/rolling composite plant. The temporal period between the last rolling pass when hot-rolling and the beginning of the cooling of the strip can be reduced without one or a plurality of roll stands having to be removed from the hot-rolling mill before the production of thick strips, or removed roll stands having to be re-installed before the subsequent production of thin strips, respectively. The product mix of the hot-rolling mill is to be expanded on account of the solution, and a wide range of high-quality steel strip is to be able to be produced.
This object of the device is achieved by a rolling mill having the features disclosed herein.
In concrete terms, the object is achieved by a roll stand having an operator-side roller housing and a drive-side roller housing, with the following features.
No working rollers and no chocks for the working rollers are disposed in the roll stand, but the roll stand instead has a stand cooler for cooling a steel strip.
The stand cooler is dimensioned so that said stand cooler can be installed in the roll stand through the operator-side roller housing of the roll stand.
The stand cooler comprises a first or lower coolant tank, in particular a water tank, and a second or upper coolant tank, in particularly a water tank, wherein the lower coolant or water tank and the upper coolant or water tank in each case have one connector for a coolant, and a plurality of cooling nozzles or cooling pipes that are disposed in the depth direction of the stand cooler, or has at least one cooling slot that runs in the depth direction of the stand cooler, such that the lower and the upper water tanks can be supplied with coolant by way of their respective connectors, the lower side of the steel strip can be cooled by the cooling nozzles, or cooling pipes, or cooling slot of the lower water tank. The upper side of the steel strip can be cooled by the cooling nozzles, or cooling pipes or cooling slot of the upper water tank.
The term “stand cooler” refers to a cooling installation which can cool a steel strip by an adjustable intensity and be installed in a roll stand, instead of chocks and working rollers. The term “stand cooler” explicitly does not refer to a cooling installation which cools the rollers of a roll stand.
The stand cooler may also have a combination of a plurality of cooling nozzles, or cooling pipes, respectively, and one or a plurality of cooling slots.
The stand cooler may be installed in the roll stand instead of chocks and upper and lower working rollers such that the roll stand of the stand cooler may cool the upper and the lower sides of a steel strip by a given intensity. Cooling here means such cooling which is comparable to the cooling in a cooling section disposed downstream of the rolling train.
It is known for an intermediate stand cooling to be used between the roll stands of a hot-rolling train so as to dissipate the heat created in the material during the deformation and to keep the strip temperature within permissible limits. This cooling is usually not dimensioned for achieving cooling of the strip in the context of this invention. In order for the cooled region to be expanded, a combination of a stand cooler with an intermediate cooling (which cools the strip only between the roll stands) is possible and advantageous for specific requirements.
For cooling, the stand cooler has an upper (second) and a lower (first) water tank which each have at least one connector for a coolant and either a plurality of cooling nozzles or cooling pipes that are disposed in the depth direction of the stand cooler, or at least one cooling slot that runs in the depth direction of the stand cooler.
The lower and the upper water tanks are supplied with coolant by the respective connector or connectors, respectively. The coolant is typically water, but may be any other coolant that may be sprayed on a strip for cooling the strip. The cooling of the lower and the upper side of the steel strip is by cooling nozzles or cooling pipes, or one or a plurality of cooling slots, respectively.
For installing and uninstalling the stand cooler in a simple manner, it is advantageous for the stand cooler to have at least two guide faces. The guide faces are connected to the lower or the upper water tank such that the stand cooler can be incorporated, for example by push-fitting into the roll stand in the width direction of the roll stand, or the steel strip, respectively, and the stand cooler in the installed state preferably bears on the guide faces.
On at least two guide faces which are connected to the upper and/or the lower water tank, the stand cooler may be incorporated into the roll stand in a simple manner, for example on rails, in the width direction of the roll stand. After having been moved in, the roll stand can remain on the rails, or be supported by the bending block, for example. The stand cooler in the installed state preferably bears on the guide faces.
Because the chocks and the upper and the lower working roller are replaced by the stand cooler, the temporal period between the finishing rolling, that is the last rolling pass in the hot-rolling train, and the beginning of the strip cooling can be drastically shortened. For example, even thick hot strips can reach the required metallurgical properties, for example, microstructure and be produced with high quality. Moreover, the section between the last rolling roll stand and the cooling section is already used for cooling.
When the stand cooler is primarily installed or uninstalled, respectively, during an interruption in the rolling operation, for example when changing the working rollers of other roll stands, it is advantageous for the stand cooler to be embodied in one piece, wherein the lower and the upper water tanks are preferably connected to one another by uprights. The stand cooler in this embodiment can be installed and uninstalled as a unit.
When the stand cooler is to be installed or uninstalled, respectively, and also during the rolling operation, it is advantageous for the stand cooler to be embodied in at least two pieces, wherein the lower and the upper water tank have in each case two guide faces. That enables the upper part of the stand cooler to have the upper water tank to be installed in the roller housing independently of the lower part of the stand cooler having the lower water tank so installed. This facilitates uninterrupted rolling operation.
As an alternative to the embodiment being in two pieces, an embodiment in one piece would also be possible, for example having a “C”-shaped stand cooler.
In the two-piece embodiment of the stand cooler, the lower water tank may be incorporated into the roll stand on exchangeable rails, for example, and may subsequently remain on the latter, or be raised or lowered by the latter, respectively. During operation, the upper water tank may be supported on the bending blocks and may be raised or lowered by the blocks. The gap between the exit openings of the water tanks and the steel strip can be set during the operation.
Simple guiding of the stand cooler is guaranteed when the lower water tank and/or the upper water tank each have two lateral support lugs, wherein each of the two support lugs has one guide face.
Since it is often necessary for the peripheral regions and the central region of the steel strip, when viewed in the width direction of the steel strip, to be cooled to dissimilar extents, it is advantageous for the lower water tank and the upper water tank to have at least two connectors. Therefore, the cooling nozzles assigned to the peripheral regions can be supplied at a lower pressure than the cooling nozzles assigned to the central region, for example.
The roll stand most typically has at least supporting rollers. In this case, the stand cooler in the state installed in the roll stand is disposed between the supporting rollers of the roll stand.
Working rollers and chocks for the working rollers are present in the normal operation of any roll stand without the stand cooler. The stand cooler of the present invention is installed in the roll stand as an alternative to the working rollers and the chocks for the working rollers. The roll stand therefore preferably additionally has the mentioned working rollers and chocks for the working rollers. The working rollers and the chocks for the working rollers herein are dimensioned, as also in the prior art, so that after the stand cooler has been uninstalled from the roll stand, the working rollers and chocks can be installed in the roll stand through the operator-side roller housing of the roll stand.
The method of the invention relating to the installation of a stand cooler for cooling a steel strip in a roll stand of a rolling train is achieved by the following method steps:
removing chocks and an upper and a lower working roller from the roll stand;
installing the stand cooler in the roll stand, wherein the stand cooler in the width direction of the roll stand or of the steel strip, respectively is incorporated horizontally through an operator-side roller housing; and
connecting the connectors of the upper and the lower water tanks to a coolant supply such that the upper and the lower sides of the steel strip can be cooled by a coolant from the cooling nozzles, or the cooling pipes or the cooling slot of the lower water tank and of the upper water tank.
The connecting of the connectors can take place, for example, by flange connections, or manually activated lever arm couplings having hose connections, or else by automatic coupling when pushing in the stand cooler.
For a discontinuously operated rolling mill, it is expedient for the installation of the stand cooler to be performed during an interruption in the operation of the rolling train.
In particular, in the case of continuously operated casting/rolling composite plants, for example of the Arvedi ESP type, it is advantageous for the installation of the stand cooler to take place during ongoing operation of the rolling train, in particular of a finishing rolling train.
According to one embodiment, one connector is supplied by a coolant at a pressure of 2 to 5 bar.
According to one further embodiment, one connector is supplied by a coolant at a pressure of 0.1 to 0.8 bar.
During operation of a stand cooler, it is advantageous for the connector or the connectors, respectively, of the lower water tank to be supplied at a higher pressure than the connector or the connectors, respectively, of the upper water tank. This can be achieved with separate pressure regulators for the upper and the lower connector. Alternatively, this can also be achieved by flow regulators operated such that the flow quantity to the lower water tank is higher than to the upper water tank (for example, 60% of the total water quantity is supplied to the lower water tank, and 40% is supplied to the upper water tank).
The aforementioned pressure ranges are not mutually exclusive, since the peripheral region of the steel strip can be cooled by a first connector having a coolant at a pressure of 0.1 to 0.8 bar, whereas the central region can be cooled by a second connector having a coolant at a pressure of 2 to 5 bar, for example.
The production of steel strips is advantageously, performed wherein a first steel strip is first rolled in at least two roll stands of a hot-rolling train. The first steel strip is subsequently cooled in a cooling section. The cooled first steel strip, for example as a slab or a coil, thereafter is conveyed away. Thereafter a stand cooler, as described above is installed in a roll stand of the rolling train. After the stand cooler has been installed in the roll stand, and a second steel strip is rolled in at least one roll stand of the rolling train, the second steel strip is cooled in at least one roll stand of the rolling train by the stand cooler, the cooled second steel strip is cooled in the cooling section, and the cooled second steel strip is conveyed away.
Another method relating to uninstalling a stand cooler from a roll stand includes the following method steps:
separating the connectors of the upper and the lower water tanks from a coolant supply;
uninstalling the stand cooler from the roll stand, wherein the stand cooler in the width direction of the roll stand is extracted (e.g. pulled out) horizontally from an operator-side roller housing; and
installing chocks and an upper and a lower working roller in the roll stand.
Separating the connectors can again be performed by flange connections, or manually activated lever arm couplings having a hose connection, or by automatic coupling when pushing out the stand cooler, for example.
Depending on the type of plant of the rolling mill, or according to the operating mode thereof, continuous or discontinuous, uninstalling of the stand cooler can take place during the ongoing operation or during an interruption in the operation of a rolling train,
It is advantageous for the cooling output of the stand cooler to be set in a model-controlled manner as a function of the material, in particular the chemical composition, the rolling parameters, thickness and speed of the steel strip, as well as the steel quality to be achieved. A cooling model as a function of the aforementioned values delivers in-line, that is during the ongoing operation of the hot-rolling train, in each case a cooling water quantity, and optionally also a width-dependent cooling water distribution for the upper and the lower side of the steel strip. The pressure and/or the flow quantity of the cooling medium through the stand cooler are set in an open-loop controlled or closed-loop controlled manner, respectively, such that upon running the steel strip through the roll stand having the installed stand coolers, cooling in the cooling section achieves the desired properties in the best possible manner.
Further advantages and features of the present invention are derived from the description of non-limiting exemplary embodiments. In the schematically illustrated figures hereunder.
The hot strip is guided on a rolling table 10 and is moved to the working rollers 5. To limit the temperature of the working rollers 5, at least one upper cooling head 8a (here, two are illustrated) and at least one lower cooling head 8b (here, two) of the working roller cooling are provided ahead, or upstream of and behind or downstream of the working rollers 5. Moreover, an upper cooling head of the intermediate stand cooling 7a is installed ahead, or upstream of the roll stand 11, and a lower cooling head of the intermediate stand cooling 7b is installed behind, or downstream of the roll stand 11. Of course, one upper and one lower cooling head of the intermediate stand cooling 7a, 7b can in each case also be disposed ahead of and behind the roll stand 11.
A pivotable loop lifter roll 9 can set the tension in the hot strip. The temperature of the hot strip before and after rolling can thus be modified. Since roll stands 11 having so-called stand chocks are known, a more detailed description of the prior art is dispensed with.
A chock 5a having an upper working roller 5 and a chock 5b having a lower working roller 5 are illustrated in a lateral view in
Two views of a stand cooler 20 are shown in
A front view of the stand cooler of
A roller housing 1 having a stand cooler 20 is illustrated in a lateral view in
An example of a plan of water lines for supplying a roll stand 11 having an installed stand cooler 20 with coolant is illustrated in
Installation of a stand cooler 20 in the roller housings 1 or a roll stand 11 is schematically illustrated in
The uninstalling of a stand cooler 20 from a roller housing 1 is not separately illustrated since the steps for the installation are simply carried out in the reverse order.
Masking of the edge regions (edge-masking) of a steel strip 50 is shown in
A stand cooler 20 in a C-shape as an alternative to the stand cooler in
While the invention has been illustrated and described in more detail by way of the preferred exemplary embodiments, the invention is not limited to the disclosed examples, and other variants can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17182794.2 | Jul 2017 | EP | regional |
The present application is a continuation under 37 C.F.R. § 1.53(b) of prior application Ser. No. 16/620,896, filed Dec. 10, 2019, which is a 35 U.S.C. §§ 371 national phase conversion of PCT/EP2018/069668, filed Jul. 19, 2018, the contents of which are incorporated herein by reference, and which claims priority of European Patent Application No. 17182794.2, filed Jul. 24, 2017, the contents of which are incorporated by reference herein. The PCT International Application was published in the German language.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16620896 | Dec 2019 | US |
| Child | 17722436 | US |
