CASTING-ROLLING SYSTEM FOR BATCH AND CONTINUOUS OPERATION

Abstract

The invention relates to a casting-rolling system (1) for generating a thin or ultra-thin band from a cast thin slab made of steel in batch or continuous operation, comprising at least one casting system (2a, 2b) for casting a thin slab with a casting thickness from 90 mm to 150 mm, preferably from 90 mm to 140 mm, particularly preferably from 100 mm to 130 mm, and a casting width of at least 600 mm, preferably at least 1000 mm, at least one continuous furnace (7a, 7b) arranged downstream of the at least one casting system (2a, 2b), as well as at least 7, preferably 8 roll stands (9, 10, 14, 15, 16, 17, 18, 19, 20) arranged downstream of the continuous furnace (7a, 7b), wherein the at least one casting system (2a, 2b) comprises a casting mould (3a, 3b) with long sides spaced apart from one another by at least 90 mm to 150 mm, preferably 90 mm to 140 mm, particularly preferably 100 mm to 130 mm, and wherein the casting-rolling system (1) has no induction heater for reheating the cast thin slab and/or the rolled band. The invention also relates to a method for generating a thin or ultra-thin band, preferably by means of a casting-rolling system (1) of this type, wherein the thin slab and/or the band does not undergo any induction heating during the method for generating the thin or ultra-thin band.

Claims

1. Casting-rolling system (1) for producing a thin or ultra-thin strip from a cast thin slab made of steel in the batch or continuous operation, comprising at least one casting plant (2a, 2b) for casting a thin slab having a casting thickness of 90 mm to 150 mm, preferably 90 mm to 140 mm, more preferably 100 mm to 130 mm, and a casting width of at least 600 mm, preferably at least 1000 mm, at least one continuous furnace (7) arranged downstream of the at least one casting plant (2a, 2b) and at least seven, preferably eight, roll stands (9, 10, 14-20), arranged downstream of the continuous furnace (7) wherein the at least one casting plant (2a, 2b) comprises a casting mold (3a, 3b), with longitudinal sides of the casting mold spaced apart at a distance of at least 90 mm to 150 mm, preferably 90 mm to 140 mm, more preferably from 100 mm to 130 mm, and wherein the Casting-rolling system (1) excludes induction heating for reheating the cast thin slab and/or the rolled strip.

2. Casting rolling mill (1) according to claim 1, characterized in that shears (13) for cutting the beginning of the leading strip and optionally the end of the strip, are arranged between the roll stands (9, 10, 14-20), preferably after the second (210) and before the third (14) of the at least seven, preferably eight, rolling mills (9, 10, 14-20).

3. Casting-rolling system (1) according to claim 1, characterized in that the roll stands (9, 10, 14-20) comprise at least one, preferably two, roughing stand(s) (9, 10), a further continuous furnace (11) arranged downstream of the roughing stand(s) (9, 10), and at least five, preferably six or seven, final roll stands (14-20) arranged downstream of the further continuous furnace (11), wherein the Casting-rolling system (1) excludes induction heating to reheat the cast thin slab and/or the roughed and/or finish rolled strips.

4. Casting-rolling system (1) according to claim 1, characterized in that the rolling gap of the last finishing roll stand (20) is adjustable to a final thickness of the thin strip to be produced from 0.8 mm to 26 mm, preferably from 1.0 mm to 25.4 mm.

5. Casting-rolling system (1) according to claim 1, characterized in that a cooling section (21), a shear (24), preferably a drum shears, and at least one reel (25a, 26b) are arranged downstream of the last roll stand (20).

6. Casting-rolling system (1) according to claim 1, characterized in that a shear (6), preferably a pendulum shear, is arranged between the at least one casting plant (2a, 2b) and the continuous furnace (7) upstream of the roll stands (9, 10, 14-20).

7. Casting-rolling system (1) according to claim 1, characterized in that two casting plants (2a, 2b) are provided, each having a pendulum shear (6a, 6b).

8. Casting-rolling system (1) according to claim 7, characterized in that each casting plant (2a, 2b) is assigned its own continuous furnace (7a, 7b), wherein a transfer device (8) for transferring a thin slab from the second casting plant (2b) is provided in or behind the continuous furnace (7a) downstream of the first casting plant (2a).

9. Casting-rolling system (1) according to claim 8, characterized in that the transfer device (8) comprises two mutually adjustable furnace segments of both the continuous furnace (7a) downstream of the first casting plant (2a) and the continuous furnace (7b) downstream of the second casting plant (2b).

10. Casting-rolling system (1) according to claim 1, characterized in that the distance between the broadsides of the at least one casting mold (3a, 3b) is at least 900 mm, preferably 1000 mm to 2000 mm, more preferably 1000 mm to 1800 mm.

11. Casting-rolling system (1) according to claim 3, characterized in that the torque of the at least one roughing stand (9, 10) is at least 1,800 kNm, preferably at least 2,000 kNm, more preferably between 2,000 kNm and 3,400 kNm.

12. Casting-rolling system (1) according to claim 11, characterized in that the torque of the at least five final roll stands (14-20) is at least 100 kNm, preferably between 100 kNm and 1400 kNm.

13. A method for producing a thin or ultra-thin strip from a cast steel thin slab in batch or continuous operation with a Casting-rolling system (1), comprising at least one casting plant (2a, 2b) and at least seven, preferably eight roll stands (9, 10, 14-20), comprising the steps of casting at least one thin slab having a casting thickness of 90 mm to 150 mm, preferably 90 mm to 140 mm, more preferably from 100 mm to 130 mm, and a casting width of at least 600 mm, preferably at least 1000 mm, heating and/or homogenizing the temperature of the thin slab in a continuous furnace (7a, 7b) and rolling the heated and/or homogenized thin slab by means of at least seven, preferably eight roll stands (9, 10, 14). 20) into a thin or ultrathin band, wherein the thin slab and/or the strip undergoes no inductive heating during the process of producing the thin or ultrathin strip.

14. The method according to claim 13, characterized in that the leading beginning of strip and optionally the end of the strip is cut off between the roll stands (9, 10, 14-20), preferably after the second (10) and before the third (14) of the at least seven, preferably eight, rolling mills (9, 10,14-20).

15. The method according to claim 13, characterized in that the rolling of the thin slab includes the roughing of the heated and/or homogenized thin slab by means of at least one, preferably two, roughing stand(s) (9, 10), the heating and/or homogenizing of the temperature of the roughed thin slab/strip in a further continuous furnace (11) and the final rolling of the roughed thin slab/or the strip to a thin or ultrathin strip by means of at least five, preferably six or seven final roll stands(14-20) arranged downstream of the further continuous furnace (11).

16. The method according to claim 13, characterized in that the casting-rolling system (1) is switchable between the batch mode and the continuous mode depending on the mass flow of the casting plant (2a, 2b) calculated as the product of casting thickness (in mm) and casting speed (in m/min).

17. The method according to claim 16, characterized in that the casting-rolling system (1) is operable in continuous operation above a threshold value for the mass flow of 350 (mm m)/min., preferably 500 (mm.Math.m)/min.

18. The method according to claim 13, characterized in that the annual output of the casting-rolling system (1) is between 4.0 and 5.0 million tons.

19. The method according to claim 13, characterized in that it is designed to produce thin or ultra-thin strips of LC, MC, HC, HSLA, DP, API, Si grades, AHSS and Corten steels.

20. The method according to claim 13, characterized in that the final rolling temperature in the last roll stand (20) is set above 820° C.

21. The method according to claim 13, characterized in that it is carried out by means of a casting-rolling system (1) according to one of claims 1 to 12.

Description

5. BRIEF DESCRIPTION OF THE FIGURES

[0025] The invention will be explained in more detail below with reference to a table and a Figure, wherein the Table and the Figure show preferred embodiments of the invention.

[0026] It is shown in

[0027] Table 1: an example calculation for the operation of an inventive casting-rolling system with eight roll stands arranged one behind the other, and

[0028] FIG. 1 a schematic view of an extended system configuration according to the invention.

6. DETAILED DESCRIPTION OF THE TABLE AND THE FIGURE

[0029] Table 1 shows exemplary experiments for producing thin strips from different steel grades with a casting-rolling system 1 according to the invention, here with a system layout having a casting plant, a downstream continuous furnace 7 and eight final roll stands 9, 10, 14-19, followed by a cooling section 21 and two reels 25a, 25b. After the first two stands 9, 10, shears 13 are arranged to cut off the strip head after exit from the second roll stand 10 and to straighten the strip on the head side.

[0030] An S315MC grade steel was cast into a thin slab having a thickness of 100 mm or 110 mm and width of 1200 mm, at a withdrawal rate of 7.9 m/min. or 7.2 m/min. This thin slab was rolled in continuous operation into a thin strip with a thickness of 1.0 mm and width of 1,200 mm. In a further experiment, the same steel grade was cast at a casting speed of 9.1 m/min. or 8.4 m/min. in continuous operation to a thin strip having a thickness of 100 mm or 110 mm and a width of 1,550 mm, and was rolled, also in continuous operation, to a thin strip having a thickness of 1.3 and a width of 1,550 mm. The mass flow (“Flow”) was 700 to about 925 mm×m/min, thus above the threshold for using continuous operation. The final rolling temperatures were above 900° C., thus significantly above the transformation temperature austenite.fwdarw.ferrite.

[0031] In another series of tests, steel grade HDT580X was cast into thin slabs with a thickness of 100 mm or 110 mm and a width of 1,200 mm at casting speeds of 9.6 m/min. or 8.8 m/min. Forming in the continuous operation resulted in a thin strip with a thickness of 1.2 mm and a width of 1,200 mm. In a further pair of experiments, the same steel was cast into a thin slab with a thickness of 100 mm or 110 mm and a width of 1,550 mm at a casting speed of 11.5 m/min. or 10.7 m/min. The mass flow (“Flow”) was 960 to 1,180 mm×m/min., thus also clearly above the threshold for continuous operation, the final rolling temperatures for the test series with the steel grade HDT580X were above 900° C.

[0032] With the same system layout, in a further series of tests, grade S315MC steel was cast into a thin slab with a thickness of 100 mm and a width of 1200 mm. From the thin slab, a thin strip of 2.30 mm thickness was rolled in batch operation. A thin slab of S315MC grade steel was also cast with a thickness of 100 mm and a width of 1,550mm, and finally rolled in batch operation to a thin strip with a thickness of 2.80 mm.

[0033] In a further series of tests, HDT580X grade steel was cast into a thin slab with a thickness of 100 mm and a width of 1,200 mm or 1,550 mm, and finally rolled into a thin strip with a thickness of 2.75 mm or 3.50 mm in batch operation. Also in batch mode, the final rolling temperatures were above the austenite.fwdarw.ferrite transition temperature to obtain a hot rolled microstructure in the final rolled strip.

[0034] FIG. 1 shows a casting-rolling system 1 in a further system layout according to the invention, wherein the casting-rolling system 1 has two casting plants 2a, 2b with respective casting molds 3a, 3b. After exit from the strand guide 4a, 4b, the solidified strand is cut by means of shears 6a, 6b, if a batch operation is to be performed on the casting-rolling system 1, and then enters a continuous furnace 7a, 7b. Between the continuous furnaces 7a, 7b, a device 8 for transferring a slab (not shown) from the continuous furnace 7b into the continuous furnace 7a is provided. After exit from the continuous furnace 7a, the slab enters a pair of roughing stands 9, 10 and is rolled in these roughing stands 9, 10 to a strip, which then enters a further continuous furnace 11 where it is reheated. After exit from the further continuous furnace 11, the pre-rolled strip can be straightened on the head side by means of shears 13, to then enter a series of final roll stands 14 to 20. Upon exiting the last roll stand 20, the strip has the desired final thickness and the desired final rolling temperature, whereupon the rolled strip is then cooled in the cooling section 21 to the temperature required for reeling. Downstream of the cooling section 21, a high speed shear 24 is provided which is used when thin strip is rolled in continuous mode and in this case has to be cut to the length of the reel without interrupting the casting-rolling process. The rolled and optionally cut thin strip can then be alternatingly wound up on two reels 25a, 25b on the fly.

LIST OF REFERENCE NUMBERS

[0035] 1 cast rolling mill

[0036] 2a, 2b casting plants

[0037] 3a, 3b casting molds

[0038] 4a, 4b strand guide

[0039] 6a, 6b shear

[0040] 7a, 7b continuous furnace

[0041] 8 device for transferring a slab

[0042] 9 roughing stand

[0043] 10 roughing stand

[0044] 11 continuous furnace

[0045] 13 shears

[0046] 14-20 finishing roll stands

[0047] 21 cooling section

[0048] 23 cooling section

[0049] 24 high-speed shears

[0050] 25a, 25b reel