Patent Application
20110247382
The invention concerns a method for producing steel flat products from continuously cast slabs of large or medium thickness or from thin slabs, which are edged and then passed through a blooming train and a finishing train.
A method for producing flat products made of steel or other metal is used to continuously cast slabs of large or medium width or thin slabs in a one-stand or multiple-stand blooming train and a roller conveyor for conveying the flat products and for reversing. The method is carried out by means of a hinged, thermally insulating roller table section provided with covering hoods and an inductive heating installation for the automatically controlled heating of near-net strip to a well-defined temperature over the length and width of the near-net strip in a multiple-stand finishing train, with a runout roller table with devices for cooling the flat product and in downstream coiling machines for coiling the finished strip.
EP 1 305 122 B1 discloses a method by which thin strip made of carbon steels or alloyed case hardening steels or heat-treatable steels is rolled in two stages with a pause between the stages for intermediate cooling by reversing on the roller table to form one or more near-net strips. The near-net strips are heated by the combined effect of the covering hoods and the heating installation to a well-defined temperature over their length and width and rolled in the multiple-stand finishing train in the two-phase range (austenite-ferrite) to form thin, high-strength finished strips, wherein, as a result of the rolling temperature in the upper austenitic range for the first deformation stage in the blooming train at a total reduction of 40-70%, the continuous casting microstructure is transformed to a rolled microstructure by complete recrystallization. Due to the fine-grained and partly work-hardened microstructure, the transformation starting temperature of the transition to the two-phase range is raised, and, in order to lower deformation resistance, the transformation time is shortened. Depending on the thickness and position of the near-net strip, the thickness of the finished strip, the feeding speed in the finishing train, and the cooling effect of a descaling sprayer upstream of the finishing train, the near-net strip is uniformly adjusted to a target temperature over its length and width by the combined effect of the closed covering hoods and an inductive heating installation in such a way that the rolling in the finishing train occurs in the two-phase range in all passes. The descaling sprayer is installed downstream of the blooming train in the direction of rolling and immediately upstream of the finishing train and serves to descale the surfaces of the slabs, not the edges.
JP 07 047 419 A discloses a hot rolling method in which an edging installation for lateral compression of the rolled strip is provided upstream of the roughing stand. In this case, a descaling installation is provided between the edging installation and the roughing stand for descaling the surfaces of the continuously cast slabs by means of water jets. Therefore, shielding plates are installed on both lateral edging rolls in the edging installation to prevent water from the descaling installation from cooling the edges of the rolled strip. The shielding plates are mounted on lateral guides, so that when there is a change in the width of the strip, the distance of the shielding plates from the rolled strip also changes.
The objective of the invention is to create a method for cleaning a metal strip during its production, which is improved compared to the prior-art methods.
In accordance with the invention, this objective is achieved with the method specified at the beginning, in which the strip edges are descaled before the edging operation is carried out on the flat products.
Without the descaling of the strip edges, there is the risk that during the edging operation the scale will be rolled into the metal, thus impairing the quality of the rolled strip. This disadvantage of strip rolled by prior-art methods is remedied by the invention.
Advantageous refinements of the invention are disclosed by the dependent claims.
The invention advantageously provides that the flat products, after passing through the blooming train and before passing through the finishing train, are subjected to an additional descaling of the edges of the strip. After this additional descaling, they can also be subjected to a further edging operation.
The strip edges of the flat products are advantageously descaled by a fluid under high pressure, especially at least one high-pressure water jet.
To achieve optimum descaling, at least one high-pressure water jet is directed at the flat products at an angle of 60-90° and especially an angle of 75° relative to the lateral surface of the flat products. In the case of a descaling station arranged upstream of the blooming train, water jets are preferably directed at the strip edges from three nozzles arranged one above the other.
The invention also concerns a rolling train for producing steel flat products from continuously cast slabs of large or medium thickness or from thin slabs with a first edging installation, a blooming train, and a finishing train.
In accordance with the invention, the rolling train is characterized in that a first descaling installation for descaling the strip edges of the flat products is arranged upstream of the first edging installation.
In addition, in a refinement of the invention, a second edging installation can be provided upstream of the finishing train, and a second descaling installation for descaling the strip edges of the flat products can be provided upstream of this second edging installation.
In an advantageous embodiment of the rolling train, the first descaling installation comprises several nozzles directed at each of the two strip edges of the flat products, especially three nozzles directed at each strip edge. In conformity with the lesser thickness of the strip after rolling, the second descaling installation has at least one nozzle directed at each of the two strip edges of the flat products. The nozzles spray a high-pressure fluid, especially water, at the strip edges.
It is advantageous especially if the nozzles are mounted on the lateral guides of the rolling train, especially on the guide plates of the lateral guides, on the ends of the lateral guides that face the edging installation, and can be adjusted in width together with the lateral guides, especially the guide plates. The mounting of the nozzles on the lateral guides or guide plates has the practical advantage that the distance of the nozzles from the edge of the strip is always constant/equal, provided that the lateral guides or guide plates are always moved out to the strip edges (which in practice is always the case). The constant distance of the nozzles from the strip edge has the advantageous effect of a constant force of impact of the water jet from the nozzles on the strip edges and thus a uniform descaling effect.
It is also advantageous if the nozzles spray the fluid onto the strip edges of the flat products at an angle of 60-90° and especially an angle of 75° relative to the lateral surface of the flat products.
The invention will now be explained in greater detail with reference to a specific embodiment.
A rolling train, which, for example, is arranged downstream of a casting machine for producing continuously cast slabs of large or medium thickness, comprises shears for cutting the cast strand into slabs and a heating-up furnace or soaking furnace for heating up the continuously cast slabs that enter the furnace cold or hot or for equalizing the thin slabs to initial rolling temperature and has a descaling installation 2 (
The flat products or strips are conveyed over rolls 3. At their two longitudinal edges, the flat products are guided by guide plates 4, 5, which extend to different positions according to the width of the flat products. This requires that the two guide plates 4, 5 are arranged symmetrically to the center in such a way that they can be shifted transversely to the rolling direction of the flat products in the direction of the double arrow A.
Two sets of three spray nozzles 6a, 6b, 6c and 7a, 7b, 7c are arranged on the front ends of the guide plates 4, 5 facing the edging installation 1 for spraying high-pressure water jets onto the two strip edges of the rolled strip. Each of the nozzles 6a, 6b, 6c, 7a, 7b, and 7c sprays conical jets of water, which overlap to provide full coverage of the lateral edges of the flat products and remove the scale.
Beyond the positions of the nozzles 6a, 6b, 6c, 7a, 7b, and 7c with respect to the running area of the rolled strip, a spray wall 8, 9 is arranged, preferably in a stationary way, on each side as spray protection. A flexible media chain 10, 11 passes through each of the spray walls 8, 9, respectively. Each flexible media chain 10, 11 contains a high-pressure hose 12, 13, respectively, for supply water from a common supply line 14. When the position of the nozzles 6a, 6b, 6c, 7a, 7b, and 7c changes according to the width of the rolled strip, the media chains 10, 11 can move and along with them the hoses 12, 13.
The nozzles 6a, 6b, 6c, 7a, 7b, and 7c are integrated in spray bars 15, 16 on both sides. The spray bars 15, 16 form the mechanically rigid end pieces of the hoses 12, 13. The spray bars 15, 16 are mounted on the guide plates 4, 5 and can be moved with them. This guarantees a constant effect of the water jets on the lateral edges of the rolled strip that is independent of the width of the rolled strip. This removes the scale in an effective way, so that the scale is not rolled into the strip in the edging installation 1, thereby improving the quality of the rolled strip.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 063 547.2 | Dec 2008 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2009/009077 | 12/17/2009 | WO | 00 | 6/17/2011 |
