Crystallizer for the continuous casting of a metal product, and corresponding casting method
Continuous casting apparatus, comprising a mold and a crystallizer for the continuous casting of a metal product. The mold is provided with primary cooling means using a cooling fluid and associated with the walls of the crystallizer. A plurality of cooling members is installed downstream of the mold to perform a secondary cooling of the product, said cooling members comprising a plurality of delivery nozzles configured to deliver a liquid for cooling the product.
1. A method for continuous casting of a metal product, to obtain a productivity between 50 ton/h and 150 ton/h, the method including the following steps:
supplying a continuous casting apparatus, the continuous casting apparatus comprising a mold and a crystallizer for endless, semi-endless, or billet-to-billet continuous casting of a metal product, the crystallizer having a casting cavity into which a liquid metal is cast, and the casting cavity defined by walls connected to each other in correspondence with edges, wherein an upper level of the liquid metal defines a meniscus, wherein said metal product is a billet and comprises an octagonal-shaped billet, and wherein said casting cavity has an octagonal-shaped cross-section with a distance between two opposite walls comprised between 110 mm and 220 mm and a length between 500 mm and 1500 mm;
providing primary cooling means to achieve a heat exchange between the walls of the crystallizer and a skin of the metal product, with a thermal flow value in correspondence with the meniscus comprised between 6 MW/m 2 and 14 MW/m 2 and with an average value comprised between 3 MW/m 2 and 5.5 MW/m 2 ;
providing a plurality of cooling members downstream of the mold to perform a secondary cooling of the cast product, wherein said cooling members comprise a plurality of delivery nozzles that deliver a liquid with a pressure at exit from said nozzles is comprised between 0.5 bar and 12 bar, and wherein specific water flow rates are between 1.2 L/kg of cast steel and 2.5 L/kg of cast steel; and
casting at a casting speed between 6 m/min and 15 m/min.
2. The method as in claim 1 , wherein a pressure of a cooling fluid of the primary cooling means in a segment corresponding to an upper zone of the crystallizer, which corresponds to a vicinity of the meniscus, is comprised between 6 bar and 20 bar, and wherein the pressure of the cooling fluid of the primary cooling means in a segment corresponding to a lower zone of the crystallizer, which substantially corresponds to an end part of the crystallizer, is comprised between 2 bar and 10 bar.
3. The method as in claim 1 , further providing that said product cast product is then subjected to rolling in a rolling line in endless mode, that is, without interruptions between continuous casting and rolling.
4. The method as in claim 1 , wherein providing the plurality of cooling members downstream of the mold comprises providing a plurality of delivery nozzles that deliver the liquid with the pressure at exit from said nozzles between 1 bar and 10 bar, in which the specific water flow rates are between 1.7 L/kg of cast steel and 2.1 L/kg of cast steel.
5. The method as in claim 1 , wherein supplying the continuous casting apparatus comprises supplying foot rolls, disposed at an exit of the crystallizer, for a guide length comprised between 150 mm and 800 mm, in which the cast product at exit from said mold follows a casting line with an aid of a plurality of guide rolls disposed directly downstream of said foot rolls following a machine radius comprised between 5 m and 25 m.
6. The method as in claim 1 , wherein providing the primary cooling means comprises providing a cooling fluid of said primary cooling means a distance from the walls of the crystallizer in contact with the liquid metal, the distance comprised between 8 mm and 10 mm.
7. The method as in claim 1 , wherein providing the primary cooling means comprises providing a pressure of a cooling fluid of the primary cooling means in a vicinity of the meniscus is comprised between 6 bar and 20 bar, and in which the pressure of the cooling fluid of the primary cooling means in a zone corresponding to an end part of the crystallizer is comprised between 2 bar and 10 bar.
8. The method as in claim 1 , wherein the primary cooling means is configured to exchange thermal flows comprised between 6 MW/m 2 and 10 MW/m 2 .