Apparatus for intensifying cooling in the casting of metal objects

Abstract: The invention relates to an apparatus for intensifying cooling in the casting of metal objects, particularly in essentially vertical continuous upward casting. In order to intensify the cooling, the part (5) of the cooler (3) that is located nearest to the casting vessel is provided with a squeeze ring (6).

Description: The present invention relates to an apparatus for intensifying cooling in the casting of metal objects, particularly in essentially vertical continuous upward casting. In order to intensify the cooling, the part of the cooler that is nearest to the casting vessel is provided with a squeeze ring. In continuous vertical upward casting, known for example from the FI patent 46,693, the cooling of a metal object is normally carried out by using the cooler of figure 1, where the cooling agent is conducted to the bottom part of the cooler through the top, via the inlet located in the vicinity of the outer wall of the cooler. In figure 1, the molten metal is conducted to a nozzle 1; in the nozzle, at the height 2, there is formed a solidification front, where the molten metal turns solid. In the cooler 3, the cooling agent is conducted, by means of the intermediate pipe 4, first downwards, through the inlet, to the bottom part of the cooler, and further back up, to the top part of the cooler, to be discharged therefrom. It is apparent that the heat content discharged through the nozzle 1 is at its highest essentially at the solidification front 2, because metal, in the course of solidification, changes state and thus emits heat according to its temperature during the change of state. While using the state-of-the-art cooler of figure 1 for instance in the casting of wire, where the casting is carried out at essentially high velocities, the increase in the temperature of the cast wire is observed as a function of time. While casting for instance copper wire at the rate of 6 m/min, the surface temperature of the wire may, after cooling, be over 500°C. Such an increase in the wire temperature generally causes the wire to break, which essentially weakens the operational efficiency of the apparatus. Among the reasons for the weakening of the cooling capacity and consequently for the increase in the wire temperature, let us point out for instance the high melting temperature capacity, which makes the temperature in the water surface of the cooler rise, so that an insulating vapor bubble is created in the cooling surface of the cooler. A further result is a thermal expansion at the bottom end of the cooler, which again creates a gap in the threading between the nozzle and the cooler. The object of the present invention is to eliminate drawbacks of the prior art and to achieve a new, improved apparatus, which is more secure in operation, so that the cooling in continuous casting is made efficient with essentially high casting velocities, too. A particularly advantageous area for applying the invention is continuous upward casting. The essential novel features of the invention are apparent from the appended patent claims. According to the invention, a squeeze ring is installed at the bottom end of the cooler. The compression stress caused by the ring prevents the gap between the nozzle and the cooler from expanding, when the bottom end of the cooler - or in the case of horizontal casting, for instance, the outermost end of the cooler - tends to expand while the cooler is heated. By means of the squeeze ring, the situation can also be reversed, so that the normal gap in between the nozzle and the cooler is even reduced, because the squeeze ring directs the thermal expansion of the cooler towards the nozzle. According to the invention, it is now possible to intensify cooling and thus prevent the breaking of the cast wire or tube while casting. DE-A 2 113 870 discloses a ceramic pressure ring to surround the nozzle of a casting apparatus as to provide a thermal insulation of the ingot mould (nozzle) against the cooling system 2 (D2, page 3, lines 1 to 11). A further object of the pressure ring is to press together the different parts of the ingot mould so as to prevent the entrance of melt into the gap between these parts. Thid document does not teach how to provide a better thermal contact between the nozzle and cooler of a casting apparatus. The abstract of JP-A 58-38639 discloses a jacket cooler surrounding the nozzle of a casting die. This jacket cooler consists of several jacket parts, each being tightened to the nozzle by means of lock bolts and springs. These fastening means are provided to realise a good contact between the cooler and the nozzle. However this solution is somewhat complicated with respect to the nozzle design, as fittings for drill bores have to be provided in the circumference of the nozzle, which fittings are causing an irregularity in the nozzle design which irregularity may cause local aberrations in the temperature profile as the nozzle material has a minor thickness in the region of the fittings. The invention is further illustrated by means of the appended drawings, where figure 1 represents a state-of-the-art embodiment, and figure 2 represents an arrangement according to the present invention, applied to a cooler of continuous upward casting. Figure 1 was already explained in the description of the prior art. Figure 2 illustrates a state-of-the-art arrangement, which is now provided with the squeeze ring of the present invention. As was pointed out above, the heat content emitted through the nozzle 1 is at its highest at the solidification front 2 and the bottom end 3 of the cooler. It is sometimes difficult to achieve sufficient cooling, and there is created a gap in between the nozzle 1 and the bottom part 5 of the cooler 3, which further weakens heat transfer from the cooler to the piece to be cast. According to the invention, the creation of this gap is prevented by means of the squeeze ring 6 arranged around the outermost part 5 of the cooler. The squeeze ring 6 brings about compression stress in the cooler, and tensile stress in the ring itself. The squeeze ring is attached to the cooler by heating, i.e. as a shrink joint. The squeeze ring is made of a material with a thermal expansion coefficient specifically lower than that of copper. One such material is invar. As was pointed out above, the invention is not restricted to continuous upward casting, but the squeeze ring pressing the gap in between the cooler and the nozzle can also be used in horizontal casting arrangements. In order to intensify the cooling, the part 5 of the cooler 3 that is located nearest to the casting vessel is provided with the squeeze ring 6.

Claims: An apparatus for intensifying cooling in the casting of metal objects, particularly in continuous casting, when the nozzle (1) of the continuous casting machine is surrounded by a cooler (3), characterized in that the cooler (3) is, at its outermost part (5), pressed against the nozzle (1) by means of a squeeze ring (6) provided around the cooler. The apparatus of claim 1, characterized in that the squeeze ring (6) is in continuous vertical upward casting arranged in between the nozzle (1) and bottom part (5) of the cooler (3). The apparatus of claim 1, characterized in that the squeeze ring (6) is in horizontal continuous casting arranged around the nozzle (1) and the cooler(3). The apparatus according to one of claims 1 to 3, characterized in that the squeeze ring (6) is attached around the outermost part (5) of the cooler in a shrink joint. The apparatus according to one of claims 1 to 4, characterized in that the squeeze ring has a thermal expansion coefficient specifically lower than that of copper. The apparatus according to one of claims 1 to 5, characterized in that the squeeze ring is made of invar.

Inventors: KOIVISTO MARKKU HERMANNI, PIETILAE SEPPO ILMARI, KOIVISTO, MARKKU HERMANNI, PIETILAE, SEPPO ILMARI, Pietilä, Seppo Ilmari
Applicants: OUTOKUMPU CASTFORM OY
Application year: 1992
Main classification: B22D11
IPC codes: B22D11