EP0787808B1 - Method and device for in-line-pickling of hot rolled strip in sequence with thin slab production - Google Patents

Description

The invention relates to a working method and a system for pickling in one Thin slab plant produced and subsequently hot rolled strip, especially low-carbon steel strip, in a directly to the Rolling process subsequent continuous process,

For certain single-purpose products in large batch sizes, there is a coupling between a thin slab caster, a hot strip mill and a pickle. To date, such couplings are not known. Considering creating a such plant and the associated method is based on the fact that thin hot strip can be produced cheaper than cold strip. When substituting Cold strip through hot strip is only possible with pickled hot strip the finished tape surface protection and coating can be applied easily can. For a sensible connection of the casting plant, hot strip mill and Pickling is assumed that the entire system must work inline, so that under Taking into account the casting and rolling process a coordination of all Speeds must be made. Duplicate plant parts are said to should be avoided as far as possible so that the system can be created inexpensively and works productively.

The main problem with the creation of a task-oriented system and with the Implementation of the working process operated on it is the adaptation of Pickling time at the speeds specified by the hot strip production; because the stain must be able to use different strip thicknesses and Process speeds in an optimized way. Pickling plants work conveniently with approx. 90 ° C cold tape.

A working process for pickling a and produced in a thin slab plant Subsequently hot-rolled strip is useful if there are large batch sizes can be processed, especially low-carbon steels are suitable for Execution of the procedure.

According to the working method is characterized by the im Claim 1 specified process steps. With these successive Process steps can be pickled a low-carbon steel strip inline, the through the thin slab caster and the subsequent hot strip mill given speeds are appropriate with appropriate coordination that To master temperature control in preparation for the pickling process as well the pickling process for the common rolling stock thicknesses and widths. The procedure can be perform inline, i.e. that following an endless rolling of the An endless pickling process is carried out. By cooling of the belt in several cooling sections and intervening recovery martensite formation in the band is guaranteed at the specified process stages avoid. The abrupt cooling of the strip from 480 ° C to 95 ° C also closes the danger of martensite formation because the transformation at 480 ° C is finished, but this cooling is helpful to form a readily detachable scale. The tape prepared in this way, which is less than 100 ° C. cold, is replaced by a number of Pickling tank led, the number of which depends on the width and thickness of each tape to be treated, possibly with individual containers over Corresponding pump systems are drained or filled with acid.

It has been found that a rolling mill with a constant 1300 mm width leaving the belt are treated at certain throughput speeds must, which depend on the thickness and width of each in the system threaded ribbon. Corresponding relationships between strip thickness and Throughput speed are specified in claim 2.

According to another feature of the invention, the working method is thereby designed that for inserting the tape into the treatment system previously threaded pilot tape is connected at the end to the tape beginning that the Pilot belt after passing through the treatment plant on one of two Coil mandrels wound up and off the belt after the winding process has ended is separated and that the tape separated from the pilot tape on the second reel dome is wound up.

The stain threading process is rarely required, for example only twice in the year. Then the pilot strip leads the hot strip beginning through the pickling line and becomes even wound on one dome of a reel. Once the hot strip is through the stain and the subsequent system parts is drawn, the connection point separated between pilot strip and hot strip and the hot strip on the second mandrel wrapped.

According to another feature of the invention, the pilot band is used by the first cathedral removed and reused at the next start.

After each production period of approx. 4 hours, the Work rolls in the hot strip mill required. The dip tubes must also be in the thin slab caster are renewed, experience has shown that a break of about 30 minutes is required. In a development of the invention Working method is therefore provided that when delivering parts of the system when Roller change, when replacing pouring tubes in the pouring system or for The stopped belt remains in the treatment plant for repair purposes and as "Pilot tape" is used for the next pickling campaign. In this way, a new threading of the tape by means of a separate Pilot tape is superfluous over a very long period of time. In one production period of about 4 hours only the strip thickness is changed, the transition pieces become cut out.

A pickling line for performing the working method according to the invention is in Claim 6 claimed

The inline arrangement of the plant components mentioned there includes the significant one The advantage that double parts of the system can be avoided. So has the invention System only one winding station with two winding mandrels, while single systems these plant parts would need double. The system can thus be very compact and operate functionally, so that large batch sizes of a certain material can be treated economically.

Within the pickling system is between the cooling devices with each subsequent compensation section and the pickling device a loop storage and a stapling device for joining the pilot tape with the one to be pickled Tape provided. The proposal deliberately dispenses with a welding device expensive tape storage required, instead, a fast-moving Stapling device proposed that only requires a short loop storage.

To the traction and transport forces required in the system inexpensively To be able to apply, there will be a facility in front of and behind the pickling facility provided for applying the tensile stresses to the belt. Any of these In a favorable embodiment of the invention, the device is in the form of a circulation chain frame designed with which the necessary transport and pulling forces can be easily applied are.

The bandwidths within the intended pickling line remain essentially the same constant, strips with a width of 1300 mm are assumed. Over a Trimming device for the longitudinal edges of the pickled strip can change the strip width in the range + 100 mm / - 100 mm become.

In a particularly favorable embodiment of the invention it is provided that the Winding mandrels arranged on a carousel reel with reversing freedom and empty space are. The pilot strip is opened by the stain when threading the beginning of the hot strip the mandrel 1 of the turning reel is wound up, the reel is turned. Once the Hot strip begins, the connection point between the pilot strip and Hot strip separated and the hot strip is on the second dome of the Reversible reel coiled.

Known turbolence pickling tanks are preferably used as pickling tanks in the pickling system provided, is injected into the treatment acid. The containers are traversed by the belt in a horizontal direction, they are over in no time Filling or emptying pump systems, also for adaptation the temperature of the acid in the pickling tanks for different pickling tasks is controllable.

Various drivers provided within the pickling system ensure transport of the tape through the entire system.

The pickling plant can be realized particularly advantageously if after a preferred feature of the invention, the process parts of the pickling plant in at least three Layers are arranged one above the other, in which the double deflected by 180 ° Belt is guided by this measure, the system builds very compact, at correspondingly large distance between the individual floors for example, 4 meters, there are only tensions in the elastic for the tape Area.

The present invention solves the coupling of a thin slab caster, a hot strip mill and a pickle for the production of thin hot strip in a surprisingly simple way. The facility is special suitable for processing low-carbon steels (e.g. ST 37, ST 52 and ST10), which can be economically manufactured in large batch sizes. The attachment is compact and simple to build and is also inexpensive to manufacture because of the Inline process, essential plant parts are only required once. The handling The system is simple and safe, so that a good cost performance ratio too is expected.

An embodiment of the invention is shown in the drawing and will described below.

In the single drawing figure, 1 is the last stand of a hot strip mill referred to, which, located immediately behind a thin slab caster, the Thin slab into a band with final dimensions in the range between 2.5 mm and Rolled out 1 mm. Followed by a driver 2 for the tape is following the Hot strip mill a cooling device 3 is provided, in which the strip of approx. Is mildly cooled to 850 ° C. to 680 ° C. On the outlet side of the cooling device 3, followed by a roller driver 4 a 38 m long compensation section is provided, the 5 is designated and in which the tape over the entire tape cross-section through the Compensation of outside and inside temperature receives a temperature of 680 ° C. To a further driver 6 for the belt is followed by a further cooling section 7 for a mild one Cooling of the belt from 680 ° C to 480 ° C, with which the belt, supported by a another driver 8 is introduced into the second compensation section 9. In this The strip cross-section is equalized to a temperature of 480 ° C equalized before the tape, supported by another driver 10 in one Loop storage is routed to where it is known in a multiple way Redirection around roles that can be changed in their intervals. At the exit this loop storage 11, the stapling device 12 is provided, in which the Start of the tape with the end of a pilot tape fed at 13 Stitch can be connected. The stapler 12 is a pair of scissors 14 upstream, in which the beginning of the band can be straightened. Supported by one Another driver 15 leaves the tape B, the stitching device, its mode of operation later is still described, and is deflected at 16 by 180 ° in a second floor in the previous direction of tape running in the opposite direction. Again supported by driver 17, the belt reaches a third cooling section, where it is very is abruptly cooled from 480 ° C to approx. 95 ° C. The cooling section is designated 18. Supported again by driver 19, the cooled strip reaches an approx. 25 m long third compensation section 30, in which the temperature of about 95 ° C above entire band cross-section is evened out. At 20 the band will turn 180 ° again redirected in its direction of passage and arrives, driven by a Circulating chain frame, which is designated 21, in the pickling device, the total of 22 is designated. The pickling system is composed of a total of 5, each 18 m long pickling tanks, which are used as turbulence pickling with a horizontal pass for the Tape are formed. The pickling tanks are designated 23 a to 23 e. About not Pump systems shown are the containers optionally filled with acid or drainable.

The pickling device is followed by the known rinsing of the belt in the Rinsing devices 24 with subsequent drying in the drying device 25 and if necessary, trimming the band edges in the trimming shear 26 Pickling device is a second circulating chain frame 27 is arranged, in which the necessary Belt tension between this and the first circulating chain frame 21 can be applied. The System ends with a drum shear 28 and the reel 29, in which the finished tape or the pilot tape can be wound up.

As already indicated in the general description of the invention, this is done Threading the tape into the stain with the help of a wound at 13, in the Plant extending pilot tape, which in the stapler 12 at the beginning of Band is connected. The pilot tape is attached together with the tape pulled through the entire plant, including the pickling device 22, and at the end the system wound on the first reel dome of the turning reel 29. Once the At the beginning of the tape in the area of the reversible reel, this is from Pilot tape cut off and passed to the second reel dome of the reversible reel 29. The pilot tape can be unwound and returned to the next threading process be while the hot strip in a known manner on the reel is coiled up. As a pilot tape, it is expedient to use a flexible one Metal fabric tape is used, which is not when moving through the 180 ° bypasses large forces required.

The entire system is in the preferred version between the last scaffolding the hot strip mill and the turning reel are 178 m long. This compact Construction can be achieved by arranging the entire system on three floors, which are 4 m apart. The first cooling section with a length of 10 m allows cooling with the specified in claim 2 Speeds, the compensation section 5 with a length of 38 m leads to the specified Temperatures. The second cooling section with a length of 15 m is the second Equalization route followed, for which a length of 38 m is also provided. For the pickling tanks are each provided for 18 m, which proved to be sufficient in order to pickle even the thickest strip to be produced in the system.

With such a system, an inline process with thin slab casting is possible for the first time, Operate rolling and pickling continuously and thus a salable To produce hot strip, in large batch sizes, the cheapest with low-carbon steel grades. Any rolling mill comes for that Processing of thin slabs known arrangement of deformation structures in Question, e.g. also a so-called planetary mill stand

Claims (12)

1. Process for pickling a strip - in particular a strip of low-carbon steel, produced in a thin slab casting line and subsequently hot-rolled - in a continuous process directly following the rolling stage, which is characterised by the sequence of the following process steps in a treatment plant:

   a) slow cooling on an initial cooling line, to 850° - 680° C, of the strip leaving the rolling process at a temperature of ≥ 880° C,

   b) equalisation of edge and core temperatures on an initial recovery line to a uniform average temperature of approximately 680° C,

   c) slow cooling, on an immediately following second cooling line, of the strip from 680° C to 480° C,

   d) equalisation of edge and core temperatures on a second recovery line to a uniform average temperature of approximately 480° C,

   e) sudden cooling of the strip from 480° C to approximately 95° C on a third cooling line,

   f) equalisation of edge and core temperatures on a third recovery line to a uniform average temperature of approximately 100° C,

   g) feeding of the strip through a number of chemical pickling vats which can be brought into or out of operation, the number of vats being set in accordance with the thickness and/or flow speed of the strip, at suitable pickling temperatures, and

   h) rinsing, drying and coiling of the pickled strip.
2. Process for pickling a strip produced in a thin slab casting line and subsequently hot-rolled as in Claim 1,
   characterised by the fact that - at a substantially constant strip width of 1300 mm - the final rolling speeds of the strip, and thus its throughput speeds through the treatment plant, are set in accordance with the final thickness of the rolled strip as follows:

   final strip thickness 1.0 mm ≈ final rolling speed 4.0 metres per second

   final strip thickness 1.5 mm ≈ final rolling speed 2.7 metres per second

   final strip thickness 2.0 mm ≈ final rolling speed 2.0 metres per second

   final strip thickness 2.5 mm ≈ final rolling speed 1.6 metres per second
3. Process for pickling a strip produced in a thin slab casting line and subsequently hot-rolled as in Claims 1 and 2,
   characterised by the fact

   that the strip is fed into the treatment plant by attaching its end to the end of a pilot strip which has been previously threaded through the plant,

   that the pilot strip, after passing through the treatment plant, is wound on to one of two reel mandrels and is separated from the strip once the winding process is complete,

   and that the strip, after separation from the pilot strip, is wound on to the second reel mandrel.
4. Process for pickling a strip produced in a thin slab casting line and subsequently hot-rolled as in Claim 3,
   characterised by the fact
   that the pilot strip is re-usable.
5. Process for pickling a strip produced in a thin slab casting line and subsequently hot-rolled as in Claim 1,
   characterised by the fact that
   when work is being carried out on parts of the plant - such as changing the rollers, replacement of casting spouts, or repair operations - the halted strip remains within the treatment plant, and is used as a pilot strip for the next pickling run.
6. Pickling plant to carry out the process as in Claims 1 to 5, consisting of the arrangement in sequence of the following process components which are capable of continuous operation:

   a) three cooling facilities (3, 7, 18), each having a following soaking line (5, 9, 30)

   b) a pickling facility (22) with several pickling vats (23a - 23e) which can be brought into and out of operation, and through which passes horizontally the strip (B)

   c) rinsing (24) and drying (25) facilities for the pickled strip (B)

   d) a cross-cutting shears (28) and

   e) at least two winding mandrels (29) for the finished strip

   having - between the process components a) and b) - a looped holding area (11) and a tack-welding facility (12) for attaching a pilot strip to the strip which is to be pickled, the pilot strip being in the form of a highly-flexible woven metal strip.
7. Pickling plant for a strip produced in a thin slab casting line and subsequently hot-rolled as in Claim 6,
   characterised by the fact
   that a facility (21, 27) is provided both before and after the pickling facility (22) for the application of tensile stress to the strip (B), this facility consisting of rotating chain frameworks.
8. Pickling plant for a strip produced in a thin slab casting line and subsequently hot-rolled as in one of Claims 6 and 7,
   characterised by the fact
   that, after the pickling facility (22), there is a trimming facility (26) for the longitudinal edges of the pickled strip (B).
9. Pickling plant for a strip produced in a thin slab casting line and subsequently hot-rolled as in Claim 6,
   characterised by the fact
   that the winding mandrels e) are arranged on a rotating coiling reel (29) with a reversing mandrel and with space for the pilot strip.
10. Pickling plant for a strip produced in a thin slab casting line and subsequently hot-rolled as in Claim 6,
    characterised by the fact that
    the pickling vats (23a - 23e) are in the known form of turbulence vats.
11. Pickling plant for a strip produced in a thin slab casting line and subsequently hot-rolled as in Claim 8,
    characterised by the fact
    that there are drive units (2, 4, 6, 10, 15, 17, 19) for the strip (B) within the plant.
12. Pickling plant for a strip produced in a thin slab casting line and subsequently hot-rolled as in Claim 6,
    characterised by the fact
    that the process components of the plant are arranged on top of each other in at least three tiers, within which the strip (B) is passed, being turned twice through 180°.

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