COOLING METHOD AND EQUIPMENT FOR CONTINUOUS UPWARD CASTING OF METALS

Abstract: A method for cooling a cast product in the essentially vertical continuous casting of metals, taking place in an upward direction, in particular in the continuous casting of wires, rods and tubes of non-ferrous metals, in which method the casting nozzle and primary cooler are at least partially inserted in the melt inside the furnace and the metal is cast through them, whereby the product to be cast is first cooled inside the casting nozzle as the primary cooling. In addition to primary cooling, the product to be cast (3, 3') is cooled outside the furnace (1) walls at least in one another cooling stage by a jet (6) of cooling agent directed onto the surface of the product to be cast, in such a way that the passage of cooling agent into the melt within the furnace is prevented.

Description: COOLING METHOD AND EQUIPMENT FOR CONTINUOUS UPWARD CASTING OF METALS The present invention relates to the method as described in the preamble of patent claim 1. The invention also relates to the equipment described in the preamble of patent claim 6. Conventional vertically upward continuous casting, where continuous casting in an upward direction takes place from the free surface of the melt, is known from e.g. Finnish patent 46693 and corresponding US patent 3,746,077. Conventional continuous casting equipment comprises a primary cooler connected to the casting nozzle as well as a secondary or re-cooler. When casting for instance wire with a diameter of 8mm, which is the most common diameter for cast copper wires, the total length of the cooler may be of the order of 2 m. The crystallization and primary cooling of the metal take place in the primary cooler, particularly in the nozzle part, the length of which is about 1 - 5% of the total length of the cooler. Secondary cooling takes place in the top part of the primary cooler and in a separate secondary cooler. The upper part of the primary cooler and the secondary cooler consist of an outer shell, a separate cooling water distribution pipe and an inner pipe. The cooling agent, such as flowing water, is outside the inner pipe and the wire, rod or tube to be cast is inside the inner pipe. There must be a clearance between the inner pipe and the wire to be cast in order to allow the billet to move without hindrance. Heat transfer occurs over the gap between the wire to be cast and the inner pipe. The relatively low investment costs of the production line have been a significant factor in the conventional vertical casting process, when used for relatively limited production levels due to the nature of the product to be cast. However, the relative investment costs of the production line could be further reduced by increasing the casting rate, in which case the number of coilers and coolers required would decrease. However, the inefficiency of the secondary cooling has been an obstacle to the increase of the casting rate. When the billet is too hot as it comes out of the cooler, it oxidizes on the surface and blackens, whereafter it is not considered acceptable for further refining. The maximum casting rate e.g. for an deoxidized cast wire with an 8mm diameter is about 5 - 6 m/min when the cooler is clean, the cooling water sufficiently cold and the melt quality acceptable. Among the obstacles to improving secondary cooling is that the inner pipe cannot be made too tight, because the billet must be able to move freely, and secondly it is not profitable to make the coolers much longer owing to the relatively small diameter of the wire to be cast. A long and thin wire easily loses the impact form made by the casting machine, which has a significant effect on wire quality. The aim of this invention is to achieve a cooling solution, which enables the increase of the casting rate in conventional upward continuous casting. Another aim of the invention is to achieve a cooling solution that enables an increase in cooling efficiency and production capacity of conventional UPCAST® equipment already in use. The invention is based on the concept whereby the upper part of the casting machine is arranged so that a jet of cooling agent is aimed directly onto the product to be cast in such a way that the cooling agent cannot travel back into the cooler and/or into the melt. The essential features of the invention will become apparent in the attached patent claims. An essential feature of the method of the present invention is that, in addition to primary cooling, the product to be cast is cooled outside the walls of the furnace at least in one another cooling stage by a jet of cooling agent sprayed on the surface of the piece to be cast in such a way that the cooling agent is prevented from contact with the melt in the furnace. The direct jet of cooling agent lowers the temperature of the product sufficiently to prevent harmful oxidation taking place. This direct secondary cooling according to the invention can increase the casting rate, thus providing more effective casting equipment with a reduced amount of cooling and coiling machines compared with conventional facilities. The cooling efficiency and production capacity of conventional UPCAST® equipment can also be increased by adding cooling equipment according to this invention. One embodiment of the method according to this invention is characterized by the recovery and reutilization of the cooling agent. Then the cooling cycle is closed and additives can be used in the cooling water. According to one advantageous embodiment of the method of this invention, the cooling agent is recovered with collection devices, such as collecting pools, arranged to the connection of the cooling agent jets. An extremely effective recirculation of cooling agent can be achieved with collecting pools. This also prevents liquid from getting into the furnace. According to one advantageous embodiment of the method of this invention, the cooling agent jet is directed onto the cast product at the point of its guiding devices, such as bending rolls. Thus, highly effective cooling impact will be achieved. On the other hand, it is possible to accomplish a highly suitable fixing point for the cooling agent jets to the connection of bending rolls. Another advantageous embodiment of the invention has the characteristic of surrounding the product to be cast with a shielding gas for at least part of the distance between the primary cooler and the cooling agent jet. This enables an increase in casting rate, while preventing the product to be cast from oxidizing between the cooler and the cooling agent jet. The invention is illustrated below by one example with reference to the attached drawings, where Figure 1 shows a vertical casting apparatus, where an arrangement according to the invention is applied, Figure 2 illustrates a detail of the apparatus according to the invention, Figure 3 shows another embodiment of the invention, Figure 4 is a diagram of the equipment according to the invention. Figure 1 shows a conventional vertical upcasting apparatus, comprising a smelting and casting furnace 1 , an essentially vertical primary cooler 2 partially set into the furnace, with the casting nozzle at least partially inserted in the melt of the furnace. The melt is solidified inside the casting nozzle and primary cooler so that the cast product formed, 3 and 3', such as wire, rod or tube, can be pulled by the drawing rolls of a drawing unit 4 over a guiding device 5, for instance a bending roll. The cast product and its route are shown in the drawing by the broken lines. The arrows indicate the direction of the cast product. The apparatus in the drawing includes at least one cooling agent jet 6, which is arranged on the outside of the furnace walls in such a way that the cooling agent to be sprayed from the jet cannot travel into the furnace. In the arrangement shown in the drawing, in addition to primary cooling, the product to be cast is cooled outside the furnace 1 walls at least in one another cooling stage by a jet 6 of cooling agent aimed at the surface of the product to be cast 3 and 3', in such a way that the passage of cooling agent into the melt within the furnace is prevented. Figure 2 shows a detail of the cooling equipment according to the drawing, where the cooling agent jets 6 are arranged to cool two separate cast products, 3 and 3'. Typically, in the direction shown in Figure 2 there will be several cast products 3 and 3' one after another (side by side). For reasons of clarity, the attachments for the cooling agent jets 6 have been omitted from the drawing. The jets are normally fixed to the cross-bracket of the support structures 14 of the bending rolls 5. Typically the cooling agent in the arrangement according to the invention is recovered and re-used. The cooling agent is collected with a collection device 7, such as collecting pools arranged at the connection of the cooling agent jets 6. The cooling agent spray jets 6 are usually arranged so that there is at least one jet per cast product 3, 3'. According to one advantageous embodiment of the invention, the cooling agent spray is directed onto the cast product 3, 3', at the point of the guiding device 5, e.g. bending roll. Figure 3 shows that the product to be cast may be surrounded by shielding gas for at least part of the distance between primary cooling and the cooling agent spray. In this case, a shielding gas space 8, such as a casing tube, is arranged in the apparatus. Typically, each cast product 3, 3' is provided with its own shielding gas space, to which the shielding gas is routed from a feed unit 9. The shielding gas, for instance nitrogen, prevents oxidation of the cast product before the cooling agent jet. Figure 4 shows a diagram of a cooling arrangement comprising a cooling agent tank 10, from where the cooling agent is recirculated with a pump unit 11 to the spray jets 6, which are preferably equipped with a valve unit 12. Part of the cooling agent flows from the spray jets 6 to the collection device 7, for example collecting pools, from where the cooling agent is returned to the cooling agent tank 10. The tank is usually provided with a heat exchanger 13 in order to regulate the temperature of the cooling agent inside the tank. The use of additives in the cooling agent, which is typically water, is possible because the circulation of the cooling agent is closed.

Claims: PATENT CLAIMS 1. A method for cooling a cast product in the essentially vertical continuous casting of metals, taking place in an upward direction, in particular in the continuous casting of wires, rods and tubes of non-ferrous metals, in which method a casting nozzle and primary cooler are at least partially inserted in a melt inside a furnace and the metal is cast through them, whereby the product to be cast is first cooled inside the casting nozzle as the primary cooling, characterized in that, in addition to primary cooling, the product to be cast (3, 3') is cooled outside the furnace (1) walls at least in one another cooling stage by a jet (6) of cooling agent directed onto the surface of the product to be cast, in such a way that the passage of cooling agent into the melt within the furnace is prevented. 2. A method according to claim 1 , characterized in that the cooling agent is recovered and re-used. 3. A method according to claim 1 or 2, characterized in that the cooling agent is collected with a collection device (7), such as collecting pools positioned at the cooling agent jet (6) connection. 4. A method according to some of claims 1 - 3, characterized in that the cooling agent jet (6) is directed onto the cast product (3,3') at the point of its guiding device (5), such as bending rolls. 5. A method according to some of claims 1 - 4, characterized in that the product to be cast (3,3') is surrounded by shielding gas for at least part of the distance between primary cooling and the cooling agent jet. 6. An apparatus for the cooling of a cast product in the essentially vertical continuous casting of metals, taking place in an upward direction, in particular in the continuous casting of wires, rods and tubes of non-ferrous metals, where a casting nozzle and primary cooler are at least partially inserted in a melt inside a furnace (1) and the metal is cast through them, whereby the product to be cast is cooled inside the casting nozzle, as the primary cooling, characterized in that the apparatus is comprised of at least one cooling agent spray jet (6) to cool the product to be cast, arranged on the outside of the furnace (1 ) walls in such a way that the cooling agent sprayed from the jet does not get to travel into the furnace. 7. An apparatus according to claim 6, characterized in that a collection device (7), such as a collecting pool, is arranged to the cooling agent spray jet (6) connection. 8. An apparatus according to claims 6 or 7, characterized in that at least one cooling agent spray jet (6) is provided for each cast product (3,3'). 9. An apparatus according to claims 6 - 8, characterized in that the spray from the cooling agent spray jet (6) is directed to hit the cast product (3,3') at the point of a guiding device (5) of the product, such as a bending roll. 10. An apparatus according to some of claims 6 - 9, characterized in that the apparatus includes a shielding gas space (8), through which the product to be cast (3,3') is routed, for at least part of the distance between primary cooling (2) and the cooling agent jet (6).

Inventors: KOIVISTO MARKKU, PIETILAE SEPPO, KOIVISTO, MARKKU, PIETILAE, SEPPO
Applicants: KOIVISTO MARKKU, OUTOKUMPU OY, PIETILAE SEPPO, KOIVISTO, MARKKU, OUTOKUMPU OYJ, PIETILAE, SEPPO
Application year: 2001
Main classification: B22D11
IPC codes: B22D11