The invention relates to a continuous casting nozzle apt for the vertical upwards continuous casting of metal into continuous cast products, said nozzle comprising a cooling mantle which includes concentrically a first outermost pipe member, a second middle pipe member, and a third inner pipe member, and therebetween two cylindrical channels co-directional with the pipe members and apt for causing a flow-through of cooling water, and said cooling mantle having a top portion and a bottom portion; a mold section, which consists of a refractory material and which has a top end with its upper fron- tal surface and a bottom end, said top end extending coaxially into an interior of the third pipe member and being attached with a heat transfer joint to this third pipe member, and said bottom end protruding from said cooling mantle; said third pipe member has an internal pipe cross-section and said mold section has an internal mold cross- section for providing the external shape of said continuous cast product, said pipe cross-section being larger than said mold cross-section.

US patent 3,872,913 discloses a method and apparatus for the continuous upward casting of profiled articles, such as bars, plates and pipes, wherein melt is drawn by means of a nozzle, establishing a chill mold above the melt surface and having its bot- torn end immersed in the melt and being connected at its upper part to a cooler support, as well as to a vacuum source, by way of a pipe that is surrounded by a cooling mantle. The cooler consists of three concentric pipes, the spaces therebetween establishing cylindrical channels for cooling water. The nozzle is constructed in one piece of a refractory material and extends by its upper end coaxially into an interior of the coo- ler. The cooler support features an opening that corresponds to an article to be cast and, with the chill mold connected with this more extensive additional cooling zone, the vacuum source enables melt to be withdrawn into a cooling zone present in the nozzle.

On the other hand, GB patent 1 307 979 discloses a continuous casting method, com- prising applying super-atmospheric pressure to the surface of molten metal in a container and thereby causing molten metal to flow to a mould in which the molten metal solidifies while extracting solidified metal progressively from the mould. In addition, the method comprises applying fluid, such as oil or an inert gas, between the mould and the solidified metal which has cross-sectionally contracted - having thus formed a gap between the mould and the metal. Therefore, adjacent to that part of the mould at which the metal begins to contract inward from the mould wall are provided a plurality of inlets into which fluid is delivered by coiled type plastic tubes passing in radial direction through a water jacket of the mould. The aim is to eliminate or minimize the entry of molten metal into a gap between the mould and the inward contracting metal, which could result from the application of super-atmospheric pressure to the melt surface. A problem with both above-described solutions is that various compounds of separating and/or filtering metals and/or alloying elements and/or oxygen may build up and deposit on the surface of a nozzle mold upwards of the point at which the cross-section of a continuously cast article begins to dwindle because of casting contraction. Such com- pounds, and particularly deposits thereof, hinder the casting process and may undermine the quality of a cast product. Such compounds or deposits are particularly susceptible to forming when the refractory nozzle mold material is graphite, which is otherwise an excellent mold material. The problems will become even more prominent should the metal to be cast be an actively reacting metal, such as aluminum or magne- sium, or the metal to be cast is some extra pure alloy, such as oxygen-free copper.

The foregoing problems can be resolved with a continuous casting nozzle of the invention, which is characterized by what is defined in the characterizing clause of claim 1 , and with a usage according to the invention, which is characterized by what is defined in claim 9.

The invention will now be described in detail with reference to the accompanying drawings.

Fig. 1 shows one embodiment for a continuous casting nozzle of the invention in a longitudinal section view along a plane I-I in fig. 2.

Fig. 2 shows the continuous casting nozzle of fig. 1 in a crosswise section view along a plane II-II in fig. 1.

Fig. 3 shows from outside one embodiment for an innermost pipe member included in the continuous casting nozzle, seen from a direction III in figs. 1 and 2.

Fig. 4 shows an end view of one embodiment for sleeves included in the innermost pipe member of fig. 3, seen from a direction IV in fig 3.

Fig. 5 shows an end view of various embodiments for one sleeve included in the innermost pipe member of fig. 3, seen from a direction V in fig. 3. Solid lines represent one variant of the embodiment, in which the radially directed openings take the form of recesses in the lower frontal surface, and dotted lines represent schematically another variant, in which the radially directed openings are holes.

The question is about a continuous casting nozzle, which is apt for the vertical upwards continuous casting of metal M into continuous cast products P, as described in parallel publications FI-46810 and US-3,872,913. For this purpose, a continuous casting nozzle 1 comprises first of all a cooling mantle 10, which includes concentrically a first outermost pipe member 11 , a second middle pipe member 12, and a third inner pipe mem- ber 13, therebetween two cylindrical channels 7a, 7b co-directional with the pipe members and apt for causing a flow-through of cooling water W - to cause a flow-through = forcing to flow through or allowing to flow through. Thus, while the continuous casting nozzle 1 is in operation, the cooling water W is first caused to flow along one channel 7a between the pipe members, which is usually, but not necessarily the outer one of these two channels, from a top portion 1y of the cooling mantle towards a bottom portion 1 a thereof, and then from the bottom portion 1 a back towards the top portion 1y, and finally out of the cooling mantle. In other words, the cooling water W flows within the cooling mantle along a U-shaped path, thus circling around a bottom edge 24 of the middle pipe member 12 as depicted in fig. 1 . In view of entering and exiting the cooling water W, the cooling mantle 10 has its top portion 1y comprising water connections 21 . The cooling mantle 10 has its top portion comprising at least attachment elements 19 of the continuous casting nozzle 1 , as well as a penetration opening 23 for extracting the cast product P as it is being produced. Hence, the cooling water W circulates over an entire length L1 of the cooling jacket 10.

The continuous casting nozzle 1 further comprises a mold section 2, consisting of a refractory material and featuring a top end 2y with its upper frontal surface 2p, and a bottom end 2a. This top end 2y of the mold section 2 extends coaxially into an interior of the above- mentioned cooling mantle 10 and is in attachment with the cooling mantle 10 by way of a heat transfer joint 6. In this context, the top end 2y represents not less than 50% of an entire length H _M of the mold section 2 and the bottom end refers to not more than 50% of the entire length H _M of the mold section 2. More specifically, the mold section 2 can have its top end 2y in attachment, by way of the heat transfer joint 6, either directly with the third inner pipe member 13 of the cooling mantle - this is the case for example when the first pipe member 1 1 and the third pipe member 13 are connected to each other by bottom edges thereof directly or by way of a lip type member or the like, as shown in publications Fl- 46810 and US-3,872,913 - or with a torus ring 25 interconnecting the third inner pipe member 13 and the first outermost pipe member 1 1 - as depicted in fig. 1. Since the torus ring 25 serves as an extension of the third pipe member 13 and as an extension of the first pipe member 1 1 , the mold section 2 can be regarded as being in attachment with the pipe members 1 1 and 13. It is obvious for a skilled artisan that this part of a continuous casting nozzle can be implemented by using intermediate designs of these two solutions or any other construction. In any event, the mold section has its top end 2y in excellent thermal contact with the cooling mantle 10, the mold section having its top end 2y over its entire length effectively cooled by water W, such that the metal M making its way in a molten condition from below into the mold section 2 has solidified substantially over its entire cross-section as early as along the length of the mold section's top end 2y. In other words, a solidification front SF of the continuous casting metal M lies within the mold section 2, more specifically within the mold section's top end 2y, as depicted in fig. 1 . The mold section's bottom end 2a protrudes from the cooling mantle 10 and is thereby in a flow communication with a space for the molten metal M, such as a furnace or a ladle or the like, in which a slag or some other layer S protects the molten metal. Experts are familiar with such furnaces and ladles, thus not described in more detail at this time. The continuous casting nozzle 1 being immersed in molten metal, such metal rises by way of the bottom end 2a of the mold section 2 to a mold cross-section A2 both in response to the hydrostatic pressure of molten metal and in response to the fact that the finished solidified cast product P is pulled upwards in a motion direction Y. At the start-up phase of continuous casting, it is also possible to use an underpressure applied to the mold cross-section A2 by way of the penetration opening 23 and further by way of the cooling mantle 10.

The mold section 2 includes an internal mold cross-section A2 for providing an external shape of said continuous cast product P. The mold cross-section A2 can be in almost any shape at all consistent with a desired profile shape. Thus, the mold cross-section A2 can be capable of providing not only a strand type cast product P but also a tubular cast product P, as indicated in publications FI-46810 and US-3,872,913. The mold cross-section A2 can be capable of forming a cast product P which is circular, elliptical or other than circular and elliptical in shape. The above-mentioned third inner pipe member 13 has an internal pipe cross-section A3 which is larger than this mold cross-section A2. In this context, the term cross-sections is used in reference to dimensions which are perpendicular to the length H _M of the mold section 2 and to the direction of the pipe members 1 1 , 12, 13 parallel thereto and to the motion direction Y of a cast product parallel thereto.

In addition, the continuous casting nozzle 1 comprises a fourth innermost pipe member 14 inside the above-mentioned third inner pipe member 13, which is why the fourth pipe member 14 features an outer surface 15, whereby it fits inside the third pipe member 13. Typi- cally, the third pipe member 13 has an internal cross-section A3 which is close to a cross- section established by the fourth pipe member's outer surface 15, such that the fourth pipe member 14 fits inside the third pipe member 13 without substantial clearance and without substantial tightness. The fourth innermost pipe member 14 is provided with a lower frontal surface 4p in abutment with the upper frontal surface 2p of the mold section 2. The fourth innermost pipe member 14 has on its outer surface at least one length channel 9, as well as in its lower frontal surface 4p, or adjacent thereto, one or more radially directed openings 8. This radially directed opening 8 is, or respectively, the radially directed openings 8 are in flow communication with the relevant, at least one length channel 9. This at least one length channel 9 and the at least one radially directed opening 8 are adapted to cause a protective cooling gas G to flow through and to be delivered inside the discussed fourth inner most pipe member 14, more specifically into an intermediate space B between the continuous cast product P rising from the mold section and the fourth pipe member 14. This fourth pipe member 14 extends coaxially inside the third pipe member 13 at least over part of a length L3 of this third pipe member 13. The intermediate space B is partially estab- lished by the fact that the fourth pipe member 14 has an internal cooling cross-section A4, whose size is equal to or larger than the mold cross-section A2, and partially by the fact that the cast product P, and thereby the cast product's cross-section A1 , contracts in re- sponse to cooling. Consequently, the cross-section A1 of the cast product P is slightly smaller in size than the mold cross-section A2. In addition, the cooling cross-section A4 of the fourth pipe member is larger than the mold cross-section A2. The intermediate space B is a sum of these differences, i.e. B = (A2-A1 )+(A4-A2). Typically, the intermediate space B has a size of not less than 0,3 mm and not more than 1 ,5 mm, preferably the intermediate space B lies within the range of 0,5 - 1 ,0 mm, but may deviate from this, depending on metal being cast and dimensions of the cast product P. The useful protective cooling gas G can be any appropriate gas which is inert and provides a high heat transfer coefficient. In this respect, helium (He) is one of the most preferred gases, but in some cases it is also possible to use argon (Ar), nitrogen (N ₂ ), carbon dioxide (CO ₂ ) and hydrogen (H ₂ ) in various combinations or individually. The gas can be selected on the basis of technical benefits as the gas consumption is generally in the order of a few liters/minute, for example 5 liters/minute, but it should be appreciated that it may fluctuate according to the size of the cast product P, i.e. the size of the cross-section A1. The length channel 9 may have cross- sections for example of 2x2 mm or other than that according to the cross-section size of the cast product P. An inlet for the protective cooling gas G, i.e. a gas connection 22 for the incoming gas in the continuous casting nozzle 1 , is located far away from the solidification front SF. Typically a distance between the gas connection 22 and the solidification front SF, which distance is substantially equal to the length L3 of the third inner pipe member 13, is for example in the order of 1000 mm, but may fluctuate within the range of 600 mm - 1500 mm or possibly even within a wider range.

The fourth innermost pipe member 14 may consist of a single component, not shown in the figures, but preferably the fourth innermost pipe member 14 consists of several sleeves 4 set axially one after the other, as shown in the figures. Either all sleeves 4, or optionally all other sleeves except for the lowermost sleeve 4, have crosswise top and bottom ends 4y, 4a thereof formed with external peripheral chamfers 16y, 16a. In addition, the outer surfaces 15 of all sleeves have the earlier described one or more length channels 9. This one or more length channels 9 extend from the peripheral chamfers 16y of the crosswise top ends to the peripheral chamfers 16a of the crosswise bottom ends. Thus, it can be appreciated that the protective cooling gas G is able to flow downwards along one or more length channels 9 of the upper sleeve, then along a lateral peripheral channel section established by the superimposed chamfers 16y, 16a in the contact area of successive sleeves, and thereafter further downwards along one or more length channels 9 of the next lower sleeve, as shown in fig. 3. One of the sleeves 4 comprises said lower frontal surface 4p, as well as said one or more radially directed openings 8 which is/are disposed either as radially directed holes 8' in line with each length channel above the lower frontal surface 4p - basically at any position above the lower frontal surface, but usually at a relatively small distance from the lower frontal surface - or as recesses 8" in the lower frontal surface 4p in line with each length channel, as shown with solid lines in figs. 3 and 5, or as holes 8' in the area of the lower external peripheral chamfer 16a, as shown with dotted lines in fig. 5, or as recesses 8". Consequently, the protective cooling gas G, flowing downwards along one or more length channels 9 of the lowermost sleeve, is able to flow by way of the holes 8' or the recesses 8" into the gap B existing between the cast product P and the fourth pipe member established by the sleeves. It is obvious that a corresponding functional configuration is obtained by constructing the fourth pipe member 14 of just one component. Under no circumstances does the supply path of the protective cooling gas G penetrate the cooling water mantle. In other words, the gas connection 22 for incoming gas, the subsequent one or more length channels 9, and the further subsequent one or more radially directed openings 8 do not extend through the first pipe member 1 1 , the second pipe member 12, and the third pipe member 13, but, instead, the path of the protective cooling gas G cir- cumnavigates these elements.

The sleeves 4 according to a first embodiment have between the cooling cross-section A4 and each peripheral chamfer 16y, 16a - innermost in diametral direction - planar end surfaces 17, whereby a desired number of the sleeves 4 can be stacked in a successively sealing manner for constructing the fourth pipe member 14. In this case, the sleeves 4 are not fastened to each other, but instead are resting typically in response to weight or possible a spring load or some other vertical force axially as an extension to each other with the end surfaces 17 in a contact 18d. In second, third, and fourth embodiments, the sleeves 4 are fastened to each other at a position between the cooling cross-section A4 and the peri- pheral chamfer 16y, 16a by means of welds 18a or threads 18b or compression joints 18c successively in a sealing manner for a stack in order to construct said fourth pipe member 14. The material for the fourth pipe member 14 and/or the sleeves 4 making up the fourth pipe member is graphite and/or ceramics or a ceramic combination and/or a metal or a metal combination, for example copper with a hard chromium plating on its internal surface. The continuous casting nozzle 1 comprises, at appropriate positions in its upper parts 1 y, the gas connections 22 for introducing and discharging the protective cooling gas G. The sleeve has a typical length in the order to 100 mm, but may fluctuate within the range of 20 mm - 200 mm or possibly even within a wider range.

The continuous casting nozzle 1 further comprises a cup-shaped thermal insulation 20 around the cooling mantle's bottom portion 1 a, the mold section 2 having its bottom end 2a extending through said thermal insulation. This cup-shaped thermal insulation 20, which consists of an appropriate refractory material, such as ceramics, can be secured around the cooling mantle's bottom portion 1 a for example by means of some fireproof paste. When using this type of configuration, the cooling mantle's bottom portion 1 a, along with its protruding bottom end 2a of the mold section 2, is immersible in a melt of the metal M as shown in fig. 1 , whereby the metal melt is able to flow into the mold section and further casting upward is enabled. The immersion depth in this type of implementation is usually within the range of 100 mm - 400 mm. It is also possible to use other types of solutions, such as a different immersion depth and/or various protections. The continuous casting nozzle 1 is operated or it works as follows. The continuous cast product P travels from the mold section 2 upwards in a motion direction Y and further in the same motion direction Y along an internal face of the fourth pipe member 14 present in the cooling mantle 10 - i.e. inside the cooling cross-section A4 - and then out of the end of the cooling mantle's top portion 1y by way of the penetration opening 23, as shown in fig. 1. The cooling water W is supplied by way of the water connection 21 to pass along one cylindrical cooling mantle channel 7a, which is co-directional with the pipe members, from the cooling mantle's top portion 1y towards the cooling mantle's bottom portion 1 a and the mold section 2 attached thereto, and thereafter further along a second cylindrical channel 7b, which is co-directional with the pipe members, back to the cooling mantle's top portion 1y and then out of the cooling mantle 10 by way of the water connection 21 . The protective cooling gas G is also supplied into the continuous casting nozzle 1 from the top portion 1y of its cooling mantle, is allowed to flow along at least one length channel 9 towards the mold section 2. Then, the protective cooling gas G is allowed to flow through a radially di- rected opening or radially directed openings 8 into an intermediate space B between the continuous cast product P and the fourth pipe member 14 in the casting product solidification front area SF or not further away therefrom than a predetermined distance H _s , at which point K the protective cooling gas G comes to contact with a surface of the cast product P. Thereafter, the protective cooling gas G is allowed to flow in the intermediate space B be- tween the fourth pipe member 14 and the cast product P towards the cooling mantle's top portion 1y, i.e. the flowing direction of the protective cooling gas G along an external surface of the cast product P is the same as the motion direction Y of the cast product itself. Thus, the protective cooling gas G flows inside the cooling mantle 10 of the continuous casting nozzle along a U-shaped path, whereby the flowing path of the protective cooling gas does not extend, nor does any of the sections of the protective cooling gas flow channels extend through the channels 7a, 7b of the cooling water W. Finally, the protective cooling gas G exits by way of the penetration opening 23. A flow rate of the protective cooling gas G along a surface of the cast product P is higher than the cast product extraction rate in its motion direction Y. This predetermined distance H _s between the cast product solidifi- cation front SF and the point K established by the radially directed opening or openings 8 is not less than 30 mm and not more than 120 mm - by way of which opening or by way of which openings 8, 8', 8" the protective cooling gas is brought to contact with a surface of the cast product P. Hence, in the novel continuous casting nozzle 1 , the protective cooling gas G is conducted along a specific channel to the vicinity of the solidification front SF in an effort to protect particularly a graphite nozzle from oxidation and from compounds of various separating metals and oxygen, which build up a continuous-casting hindering deposit of foreign metals and oxygen on a surface of the nozzle at the cast product solidification point or its immediate vicinity. At the same time, the cast product P retains a higher purity regarding the effects of normal atmosphere. This presently described continuous casting nozzle 1 is excellently applicable to the casting of aluminum and aluminum alloys, as well as copper alloys, such as oxygen-free copper. In the above-described construction, the concentric components of the cooling mantle 10, i.e. the first outermost pipe member 1 1 , the second middle pipe member 12, the third inner pipe member 13, and the fourth innermost pipe member 14 can be in any rotated position relative to each other and still both the path of the cooling water W and the paths or channels of the protective cooling gas G are always open. The malfunction possibilities are thereby minimized. Moreover, the construc- tion can be implemented by using threaded components.