CN1364103A - Method and rolling installation 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

Method and rolling equipment for austenitic thin strip rolling

The invention relates to a method for the austenitic rolling of thin strip in a hot strip mill, preferably in a CSP plant, which consists of a multi-stand train, a cooling strip for cooling the rolled strip The device and the output roller table of the post-coiler for coiling the strip.

At present, hot rolling plants for the manufacture of strip are generally arranged and operated in such a way that the deformation in separate rolling stands takes place in the austenitic zone. In other words, it is necessary to ensure that the rolling temperature in each rolling stand is higher than the GOS line of the iron-carbon phase diagram. It is only after the last rolling pass that the strip is cooled to the coiling temperature in the cooling section, resulting in a structural transformation.

According to the different carbon content of the strip, in the above method, the finish rolling temperature is about 890°C-930°C. The finish rolling temperature is controlled by changing the finish rolling speed, and the finish rolling speed has an influence on the natural cooling and the heat supply brought by the rolling process.

This method can also be successfully used for strip thicknesses greater than the minimum strip thickness which, depending on the type of rolling mill, lies within the order of magnitude of 1.3 mm. If the strip thickness is smaller than this, the required rolling speed of up to 12 m/s is obtained, which can no longer be controlled during the free discharge of the delivery roller table after the rolling mill, because, on the delivery roller table, The belt is no longer transported flawlessly at such high speeds, so it cannot be rolled up in the end.

In addition, heat-related problems arise, namely that the rolling process is characterized by strip temperature instabilities (temperature differences over the width and thickness of the strip, during rolling in the finishing Than, the tail of the rough-rolled strip is subjected to strong cooling).

The current direction of development is also to manufacture strips with a thickness of less than 1.3 mm. In this case, attempts have been made to achieve a controllable finishing speed in this way by lowering the finishing temperature.

In DE19538341A1 a production plant is described for the manufacture of strips as thin as 1 mm, in which first austenitic rolling is carried out to 5 mm-15 mm, and subsequently, the strip is ferritic rolled above 850 °C to about 1mm. To this end, firstly, the first stand of the rolling mill is designed to be reversible, and at least one coil furnace is respectively set up before and after the reversible stand, wherein the front coil furnace and the subsequent reversible rolling stand A controllable cooling device is provided between them.

In an unpublished European patent application EP97120406.0, in order to obtain a uniform strip temperature (so that it is possible to roll a strip thinner than 1 mm), such a scheme is proposed, that is, in the reversing rolling mill stand and the strip precision A soaking furnace is arranged between the rolling mills, which ensures a total heating time for the rough-rolled strip with a rough-rolled thickness by means of a number of support plates for the uniformly heatable strip. This total heating time is the hot strip Several times the rolling time in the finishing mill. As a result, a pre-rolled strip with a more uniform temperature is produced, thus providing the best possible prerequisites for rolling the thinnest strip.

In order to be able to austenitically roll thin strip with a CSP plant, very high output speeds (eg up to 20 m/s) are required. However, the safe conveying of the rolled strip on the run-out table can only be carried out at a speed of up to 12 m/s, or only during the time period in which the strip comes out of the last stand. Before the head of the material is clamped by the downcoiler and rolled up. Subsequently, the mill can be accelerated to a higher output speed. In such a rolling schedule, the different rolling conditions and the large distance between the last stand and the downcoiler lead to undesired mechanical material properties of the rolled strip head and tail. This property was only achieved after rolling about 130 meters of strip, and as a result, the mill yield was reduced.

Based on this known prior art, the task of the present invention is to propose a method with which the higher rolling speeds or output speeds that occur when producing thin strips up to 1.2 mm can be controlled by simple means , thereby avoiding as much as possible the disadvantages of known methods and devices, such as low yields or high installation costs associated with additional work costs for additional heating or cooling.

In a hot strip rolling mill, preferably in a CSP rolling mill, the proposed object is achieved by the characterizing features of claim 1 . The dependent claims present advantageous refinements of the invention.

For rolling ultra-thin strips, according to the invention, a coiler, such as a rotary coiler, is swung into the rolling line after the last rolling stand but before the run-off table. Now, the first strip material is wound into a first coil on the first mandrel of the coiler at high output speed, and the mandrel of the rotary coiler is subsequently rotated by 180°. While the first strip is unwound again at a lower output speed (up to 12.5 m/s) and sent to the downcoiler via the output roller table, the second mandrel of the rotary coiler is rotated at a high output speed Wind out the second tape roll. Subsequently, the two mandrels of the rotary coiler are turned again by 180° and the subsequent strip can be coiled. In this way, coiling and uncoiling can be performed continuously.

Immediately after the strip comes out of the last stand, the strip is coiled at a very high strip finish or output speed, but then opened again (or now at a significantly lower conveying speed), whereby First, separate the rolling mill row from the output roller table, so that high final rolling speed or output speed and low conveying speed can be achieved at the same time, and no longer cause problems and shortcomings due to excessive output speed. When the output speed (V This is also the case when _W ) ≥ 12.5 m/s equals 20 m/s and the conveying speed (V _T ) ≤ 12.5 m/s is significantly slower.

The coiling and uncoiling measures have no effect on the sequence of slabs or the sequence of coils, since, according to the invention, during uncoiling, the subsequent coiling of the strip has already taken place. Since the coiling ends earlier than the simultaneous opening of the original coil due to the high speed, once the uncoiling is completed, the rotary coiler immediately rotates 180°. Thus, short pauses occur in the coil being wound up, which advantageously leads to temperature equalization of the different strip parts. A further advantage of the present invention is that after completion of coiling and uncoiling, the strip ends are exchanged and the original strip ends are now sent to cool down via the delivery roller table.

A rolling plant carrying out the method according to the invention comprises a coiler, such as a rotary coiler, which can be swung into the rolling line immediately after the last rolling stand and before the run-off table, which has two offsets 180° take-up mandrel and it is designed so that its mandrel can turn 180°.

In the following, other advantages, details and features of the present invention will be described in detail in conjunction with an embodiment shown in a schematic diagram. in:

Figure 1 shows a part of a typical rolling mill of a rotary coiler according to the invention;

Figure 2 is a simplified diagram of different strip speeds;

Fig. 3 is a partial top view of the rolling mill shown in Fig. 1;

Fig. 4 is a top view of a part of a rolling mill according to another embodiment of the present invention.

FIG. 1 shows a rolling mill 1 (which is a two-strand rolling mill) comprising a shear 2 , a soaking furnace 3 , another shear 4 and a multi-stand train 5 . A run-off table 10 with a cooling device 6 is located behind the rolling mill train 5, followed by a deflection roll 9 with an undercoiler 7 behind it for coiling the finished strip.

According to the invention, in such a conventional hot strip rolling mill, immediately after the last stand of the rolling mill train 5, a rotary coiler 8 with two coiling mandrels 8', 8" is swung into the rolling mill. Line. The strip from the rolling mill leaves the rolling line and is fed into the mandrel 8' of the rotary coiler 8 through the first turning roll 9' as a coiled strip 11. Staggered from the first mandrel 8' The second mandrel 8 " of 180° passes the second deflection roller 9 " and returns the strip to the rolling line before the output roller table 10 as uncoiled strip 12 . The two winding mandrels 8 ′ of the rotary coiler 8 , 8" can be designed to work independently of each other, thereby achieving different coiling and uncoiling speeds according to the invention.

In FIG. 2 , the strip speed in a hot strip rolling mill is shown schematically corresponding to FIG. 1 . The thin strip is cast at speed V _Bramme or V _B and fed into soaking furnace 3 and rolling train 5 . Subsequently, an output speed V _Walzen or V _W occurs at which the finished rolled strip 11 is coiled in the rotary coiler 8 . Subsequently, the preceding strip is conveyed as uncoiled strip 12 from the rotary reel 8 to the downcoiler 7 at the speed V _Transport or V _T via the delivery roller table 10 .

In FIG. 3 a detail from FIG. 1 is shown in a schematic plan view. The strip (coiled strip 11 ) coming out of the rolling mill 5 at a coiling speed V _W is wound onto a mandrel 8 ′ of a rotary coiler 8 . Simultaneously, the second mandrel 8" of the rotary coiler 8 arranged behind the mandrel 8' in the conveying direction pays out the uncoiled strip 12 at the conveying speed V _T .

Once the uncoiled strip 12 leaves the mandrel 8" completely (due to the high take-up speed V _W , the take-up strip 11 has been fully rolled up in advance), the mandrels 8', 8" rotate 180° around the center of rotation 15, As a result, the two mandrels 8', 8" exchange positions. The now free mandrel 8" is located in the place where the former take-up mandrel 8' was, while the full take-up mandrel 8' Located 8” from the original unwinding mandrel.

In order to be able to carry out the coiling and uncoiling by mandrels 8', 8" in this exchange of positions, the two mandrels 8', 8" are offset from each other by 180° so that each mandrel 8', 8" is in position Replaced in the same orientation as the original mandrel.

The rotation of the mandrels 8', 8" for indexing can be done in either direction according to the double arrow 14, or in one direction only, such as clockwise only.

In order to abandon the measures of the invention when rolling thick strips at a relatively low output speed V _W and directly send the strips to be cooled, the coiler 8 is arranged as indicated by arrow 13 so that it can be swung in and out of the rolling sideways. line. However, swinging in and out of the rolling line from below (not shown in the figures) is also possible.

A plan view of another possible embodiment of the invention is shown in FIG. 4 . In the example of Fig. 4, the two mandrels 8', 8" are not arranged one behind the other as in Fig. 3 in the conveying direction, but are arranged side by side. Here, the position exchange is also via the two mandrels 8' , 8 "rotate 180 ° along the direction of arrow 14, but here it is carried out around the center of rotation 16 that is arranged on the coiling strip 11 and the unwinding strip 12.

In the following, the tacts occurring during the manufacture of thin strips are shown in a table by way of example. Thin slab casting, 50 mm square Rolled to 0.8 mm, coiled Uncoiling/Cooling V _B ＝5.5m/min V _W ＝20m/s V _T ＝12.5m/s 9min/thin slab (double stream production equipment) Coiling 2.6min, interruption 1.6min, swing 0.3min Swing = 0.3min, Unwind = 4.2min Thin slab sequence = 4.5min Volume sequence = 4.5min Volume sequence = 4.5min

It can be seen from the table that, through the measures according to the invention, an offset occurs according to the sequence of slabs by which the rolled strip is sent for cooling.

The invention is not restricted to the embodiment described and shown, but the invention can be realized if the basic idea of the invention is always maintained, that is to coil the strip directly after rolling at a high output speed and uncoil it again at a correspondingly low speed. The design structure of existing or newly conceived hot strip mills is adapted to the situation that arises.

Claims (6)

1. A method for austenitic thin strip rolling in a hot-strip mill, preferably a CSP plant, comprising a multi-stand mill train (5), a cooling strip for cooling the rolled strip The device (6) and the output roller table (10) of the post-coiler (7) for coiling the strip are formed, and it is characterized in that the strip is directly on the last frame of the train (5) from the rolling mill After coming out as a coiled strip (11), it is wound up on a coiler (8) at its output speed (V _W ) and then conveyed at a slower rate as an uncoiled strip (12). Velocity (V _T ) is turned on. 2. The method according to claim 1, characterized in that output speed (V _W ) ≥ 12.5 m/s, delivery speed (V _T ) ≤ 12.5 m/s. 3. The method according to claim 1 or 2, characterized in that it has a continuous process in which the coiled strip ( ₁₁ ) is wound to a coiling machine (8) such as a mandrel 8' of a rotary coiler, and then, after the coiler (8) has rotated 180°, it is opened as an uncoiled strip (12) with a changed delivery speed (V _T ). A strip coil, wherein the subsequent strip is simultaneously wound up on the second mandrel 8" of the coiler (8) as a coiled strip (11) at the strip output speed ( _Vw ). 4. A rolling plant for rolling austenitic thin strip in a hot strip mill, preferably a CSP plant, for carrying out the method at least as claimed in one of the preceding claims, wherein the hot strip mill consists of a plurality of The stand rolling mill train (5), a delivery roller table (10) with a cooling device (6) for cooling the rolled strip and a post-coiler (7) for coiling the strip consists of It is characterized in that a coiler (8) which can rotate 180° and is preferably a rotary coiler is arranged between the last stand of the rolling mill train (5) and the output roller table (10). 5. The rolling plant according to claim 4, characterized in that the coiler (5) is equipped with two coiling mandrels 8' and uncoiling mandrels 8" which are independent of each other and are offset relative to each other by 180°. 6. Rolling plant according to claim 4 or 5, characterized in that the coiler (8) is designed to be swung into the rolling line.

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