DE19925536A1 - Method and rolling plant for the austenitic rolling of thin strips - Google Patents

Abstract

A disadvantage in the production of thin strips by austenitic rolling in the hot strip trains is that very thin strips are delivered at high speeds (vW), which can cause difficulties for the successive processing steps. According to the invention, the strip is wound onto a rotor winder (8) as wound strip (11) immediately after exiting the last rolling stand of the rolling train (5) with a high delivery speed (vW). Said strip is then unwound at a low transportation speed (vT) as unwound strip (12).

Description

The invention relates to a method for austenitic rolling of thin strips in hot strip mills, preferably in CSP plants, consisting of a multi-stand rolling mill, an outlet roller table with facilities for cooling the Rolling strip and downstream winding machines for winding of the tape.

Hot rolling plants for the production of strips are today in the generally designed and operated in such a way that the transformation into the individual rolling stands are austenitic. So it will ensured that the rolling temperature in each Roll stands above the GOS line of the Iron-carbon chart lies. Only after the last one Roll pass is used to cool down to the reel temperature Structural transformation in the cooling section.

Depending on the amount of carbon in the tapes, the process described above the finish rolling temperature at about 890 up to 930 ° C. Compliance with the finish rolling temperature is ensured by Change of the final rolling speed controlled that one Influence on natural cooling and on the supply of heat through the rolling process.  

This can also be used without problems for strip thicknesses above a minimum strip thickness, depending on the rolling mill type in the Of the order of 1.3 mm. Will this strip thickness undershot, the required level is reached Rolling speed values of over 12 m / s in the open No outlet on the outlet roller table behind the rolling mill can be mastered more because the hot strip on the Exit roller table at this high speed no longer properly managed and not reeled afterwards can be.

There is also the thermal problem that the Rolling process due to non-constant strip temperatures is marked (deviations across the bandwidth and Strip thickness, stronger cooling of the sliver end in comparison to the opening head during rolling in the finishing train).

Development trends are moving in the direction, including strip thicknesses below 1.3 mm. Here u. a. tries, to lower the finish rolling temperature so as to controllable final rolling speeds.

DE 195 38 341 A1 describes a production plant for the Production of thin strips up to 1 mm thick described, at which is first austenitic rolled to 5 to 15 mm and later at temperatures above 850 ° C ferritic rolling takes place on a strip thickness of approx. 1 mm. First of all, the first stand of the rolling mill is as Reversing scaffold trained, the at least one reel furnace is upstream and downstream, being between the superior Coiler furnace and the following reservation scaffold a controllable Cooling device is provided.  

In a unpublished European Patent application (EP 97 120 406.03 is used for equalization of strip temperatures - so that hot strip with thicknesses below 1 mm can be rolled - suggested between the Reservation stand and the hot strip finishing line one Arrange the equalization furnace by a number of Recording places for heatable tapes a Total heating time for each support strip with the support strip thickness ensures that a multiple of the rolling time in the hot strip finishing mill is. This creates a supporting strip with a homogeneous temperature which creates the best possible conditions for rolling Tapes with minimal end tape thicknesses can be created.

In order to be able to roll thin strips austenitically on CSP systems, are extremely high outlet speeds (up to approx. 20 mIs) required. Secure transport of the rolled strip on the exit roller table is only possible at a maximum of 12 m / s and until the last scaffold Leaving band tip is caught by the underfloor reel and is wrapped up. Only then can the road go higher Outlet speeds are accelerated. At a Such rolling strategy lead different Rolling conditions and the large distance between the last Scaffolding and the underfloor reel to make the rolled Band start not the desired mechanical Has material properties. Only then will these reached when approx. 130 m have already been rolled, which means that Spreading the road is reduced.

Based on this known prior art, it is Object of the invention to provide a method by which  when producing thin strips below 1.2 mm resulting higher final rolling speed or Outlet speed can be controlled with simple means is that in known methods and systems resulting disadvantages, such as a bad one Application or a high expenditure on equipment associated with additional operating costs through additional heating or Cool, largely avoided.

The task is performed on a hot strip mill, preferably in the case of a CSP system by the characteristic Features of claim 1 solved. Advantageous configurations of the inventions are specified in the subclaims.

For the rolling of extremely thin strips, according to the Invention a winding machine, for example a rotor reel, behind the last rolling stand and before the exit roller table pivoted into the rolling line. The first volume is now with its high exit speed on the first mandrel of the Rotor reels are wound into the first coil, then the mandrels of the rotor reel swiveled through 180 °. While now the first Belt with the slower transport speed (maximum 12.5 m / s) again and over the outfeed roller table to the Underfloor reel is transported on the second mandrel of the rotor reel the next following band with its high Exit speed wound up to the second coil. After that the mandrels of the rotor reel are swiveled again by 180 ° and the next tape can now be wound up. To this The winding and unwinding can be carried out continuously become.

By leaving the tape immediately after it exits  the last rolling stand with its high final rolling speed or exit speed wound up, but then immediately is handled again - and now with the clear slower transport speed - is the rolling mill from Unraveled roller table, which means high end rolling or Outlet speeds and low Transport speeds are possible at the same time and none Disadvantages and problems from too high Leakage speed can be caused more, even then not if the exit speed is <12.5 m / s and for example, is 20 m / s and the transport speed is significantly slower at 12.5 m / s.

The slab or coil sequence is influenced by the Measure of winding and unwinding not exercised, because according to the Invention while unwinding the winding of the next volume is performed. Because the winding up ended faster than because of the higher speed the simultaneous unwinding of the previous tape is only then the rotor reel swiveled through 180 ° when the Unwinding is finished. It therefore arises in wound coil a little break, which is beneficial too temperature compensation of different belt areas leads. Another advantage of the invention is that After winding and unwinding the tape ends together are swapped and now the original tape end first the outlet roller table is led to the cooling.

A rolling mill for performing the invention The method has a winding machine, for example one Rotor reel, which is immediately behind the last rolling stand and can be swiveled into the rolling line before the exit roller table  is arranged and the two offset by 180 ° Winding mandrels and with its thorns by 180 ° is designed to be pivotable.

Further advantages, details and features of the invention are described below using a schematic Illustrated embodiment shown in more detail explained.

Show it:

Fig. 1 shows a section of a conventional rolling mill reel having a rotor according to the invention,

Fig. 2 is a diagram of the different possibilities Bandgeschwindig,

Fig. 3 is a plan view of a detail of the rolling mill shown in FIG. 1,

Fig. 4 is a plan view of a section of a rolling mill with a further embodiment of the invention.

Fig. 1 shows a continuous caster 1 (it is a two-strand system), followed by a pair of scissors 2 , a compensating furnace 3 , another pair of scissors 4 and a multi-stand mill 5 . Behind the rolling mill 5 there is the run-out roller table 10 with devices 6 for cooling and finally a deflection roller 9 with a subsequent underfloor reel 7 for winding up the finished strip.

According to the invention the rolling mill ', the rolling line, "pivoted 8 in the rolling line. The tape from the roll stand is leaving via the first deflecting roller 9' is in this conventional hot strip mill immediately downstream of the last rolling stand 5, a rotor reel 8 with two Aufwickeldornen 8 in this rotor reel 8 on the mandrel 8 'as a take-up belt 11. From a second mandrel 8 ", which is offset by 180 ° with respect to the first mandrel 8 ', the tape is used as an unwinding tape 12 via the second deflection roller 9 " in the rolling line to the exit roller table 10 The two winding mandrels 8 ′, 8 ″ of the rotor reel 8 are designed to be drivable independently of one another, so that the different winding and unwinding speeds are made possible according to the invention.

In Fig. 2, adapted to Fig. 1, the strip speeds prevailing in the hot strip mill are plotted. The thin slabs are poured at the speed v _slab or v _B and moved into the equalization furnace 3 and into the rolling mill 5 . The exit speed v _rolls or v _W follows, with which the finished rolled thin strip 11 is wound up in the rotor reel 8 . The previous belt is then conveyed from this rotor reel 8 as an unwinding belt 12 at the speed V _Transport or v _T to the underfloor reel 7 via the outfeed roller table 10 .

In Fig. 3, a partial section of Fig. 1 is shown in a schematic plan view. The band emerging from the roll stand 5 at the winding speed v _W - the winding band 11 - is wound onto the mandrel 8 'of the rotor reel 8 . At the same time, the unwinding tape 12 is unwound from the second mandrel 8 ″ of the rotor reel 8 arranged behind the mandrel 8 ′ in the transport direction at the transport speed v _t .

As soon as the unwinding belt 12 has completely left the mandrel 8 "- because of the higher winding speed v _W , the winding belt 11 has already been completely wound up - the mandrels 8 'and 8 " are pivoted about the pivot point 15 by 180 °, as a result of which the two mandrels 8 'and 8' exchange their positions. the now empty unwinding mandrel 8 'is then in the position of the previous winding mandrel 8' and the filled winding mandrel 8 'in the position of the previous unwinding mandrel 8 ".

So that during this change of position the winding and unwinding on the mandrels 8 'and 8 "can take place, the two mandrels 8 ' and 8 " are arranged offset from one another by 180 °, so that each mandrel 8 ', 8 "after a change of position in the same Alignment is like the previous thorn.

The pivoting of the mandrels 8 , 8 "for changing the position can be carried out in any direction according to the double arrow 14 or else in only one direction, for example only in the clockwise direction.

So that when rolling thicker strips at a lower exit speed v _W the measures of the invention can be dispensed with and the strip can be fed directly to the cooling system, the reel 8 is arranged in the direction of the arrow 13 so that it can be swung in and out laterally into the rolling line. Swinging in and out is not possible in the drawing figures, but can also be carried out from below into the rolling line.

In FIG. 4 a top view of a further possible embodiment of the invention is shown. In this example of FIG. 4, the two mandrels 8 ', 8 "in the transport direction are not arranged one behind the other as in FIG. 3, but next to one another. The change of position also takes place here by rotating the two mandrels 8 ', 8 " by 180 ° in Direction of arrow 14 instead of, but now around the fulcrum 16 arranged laterally next to the winding belt 11 and the unwind belt 12 .

The table below shows the resultant cycle times for the production of a thin strip using an example.

The table shows that the measure of Invention only according to a time difference comes a sequence of slabs with which the rolled strip of Cooling is supplied.

The invention is not based on the illustrated and cited Examples are limited but can be according to training an existing one or a new one Hot strip mill can be adapted to the given conditions, if the basic idea of the invention is retained, that Thin strip immediately after rolling with its high Exit speed wind up and with accordingly unwind at low speed.

Claims (6)

1. A method for the austenitic rolling of thin strips in hot strip mills, preferably in CSP plants, consisting of a multi-stand rolling mill ( 5 ), an outfeed roller table ( 10 ) with devices ( 6 ) for cooling the rolled strip and downstream winding machines ( 7 ) for winding the Belt, characterized in that the sand immediately after leaving the last roll stand of the rolling train ( 5 ) is wound up with its exit speed (v _W ) as a winding belt ( 11 ) on a winding machine ( 8 ) and immediately thereafter with a slower transport speed (v _T ) than Unwinding tape ( 12 ) is unwound again. 2. The method according to claim 1, characterized in that the exit speed (v _W ) ≧ 12.5 m / s and the transport speed (v _T ) ≦ 12.5 m / s. 3. The method according to claim 1 or 2, characterized by a continuous process, wherein the take-up belt ( 11 ) with its exit speed (v _W ) on a mandrel 8 'of a winding machine ( 8 ), for example a rotor reel, wound up and then after pivoting the Winding machine ( 8 ) is rewound by 180 ° with changed transport speed (v _T ) as unwinding belt ( 12 ), with the following belt simultaneously on a second mandrel 8 'of the winding machine ( 8 ) as a new winding belt ( 11 ) with its exit speed (v _W ) is wound up. 4. Rolling plant for the austenitic rolling of thin strips in hot strip mills, preferably in CSP plants, consisting of a multi-stand rolling mill ( 5 ), an outfeed roller table ( 10 ) with devices ( 6 ) for cooling the rolled strip and downstream winding machines ( 7 ) for winding the Belt for carrying out the method according to one or more of the preceding claims, characterized in that a winding machine ( 8 ), preferably a rotor reel, is arranged between the last rolling stand of the multi-stand rolling mill ( 5 ) and the outfeed roller table ( 10 ). 5. Rolling plant according to claim 4, characterized in that the winding machine ( 8 ) with two mutually independent, 180 ° offset from each other 8 'and unwinding mandrels 8 "is formed. 6. Rolling plant according to claim 4 or 5, characterized in that the winding machine ( 8 ) is designed to be pivotable into the rolling line.