WO1997014519A1

WO1997014519A1 - Continuous casting plant for casting metal filaments directly from liquid metal

Info

Publication number: WO1997014519A1
Application number: PCT/FR1995/001379
Authority: WO
Inventors: Dominique Loison; Michel Hirtzmann
Original assignee: Unimetal
Priority date: 1995-10-19
Filing date: 1995-10-19
Publication date: 1997-04-24
Also published as: AU3808395A

Abstract

The invention relates to a continuous casting plant for casting metal filaments, of the type comprising two internally cooled cylinders (1, 1'), having horizontal longitudinal axes and provided with means for rotating them in reverse directions about said axes, and of which the side surfaces comprise grooves (6-14, 6'-14') which are spaced between each other and wherein takes place the solidification of said filaments, two side faces (46, 47) applied against the planar extremities (2, 3, 2', 3') of said cylinders (1, 1') so as to define, in cooperation with said cylinders (1, 1') a laterally closed casting space, and means for introducing the liquid metal into said casting spaces; the spaces separating said grooves are comprised of projecting parts (15-23, 15'-23') with respect to the rated diameter (D) of the cylinder and each of said protecting parts (15-23, 15'-23') of one of said cylinders (1, 1') penetrates inside a groove (6-14, 6'-14') of the other cylinders (1, 1') so as to fill said groove partially, a functional play been provided between said protecting parts (15-23, 15'-23') and said groove (6-14, 6'-14').

Description

INSTALLATION OF CONTINUOUS CASTING OF METAL FILAMENTS DIRECTLY FROM LIQUID METAL

The invention relates to the field of continuous casting of metal products, in particular steel. It relates more particularly to direct casting, from liquid metal, of products or semi-finished products in the form of small section filaments.

Usually, steel wires having a diameter on the order of a millimeter or centimeter are obtained by a relatively long manufacturing process, which involves expensive installations. According to this classic process, the liquid steel is first poured and solidified continuously in the form of semi-finished products of round, square or rectangular section. These must then undergo several rolling stages before a wire of the desired diameter is obtained. It is easily understood that it would be desirable to shorten this process, for example by casting the liquid steel (or any other metal) directly in the form of filaments which would have a section as close as possible to the section desired for the finished products. This approach would be analogous to that currently followed for steel sheets and strips, where it is sought to eliminate the hot rolling step by casting the liquid steel directly in the form of a thin strip, in accordance with which already exists for low-melting metals such as copper and aluminum.

Document JP 6292439 proposes, for this purpose, to carry out the casting of the filaments between two cylinders with horizontal axes rotated in opposite directions and energetically cooled internally. These cylinders are contiguous, each have a series of semicircular section grooves, and are arranged in such a way that their respective grooves face each other to define passages of circular section at the contact level of the cylinders. The diameter of these passages is equal to that of the filament that we want to cast. On the other hand, these grooves overhang internal channels to the cylinders where the coolant. Outside the grooves, the outer surface of the cylinders is flat, and is formed by an area that is not preferably cooled. To this end, a mass of insulating material is exposed on the surface of the cylinder or is inserted inside the cylinder a short distance from this surface. It is these non-preferably cooled zones which constitute the contiguous parts of the cylinders during casting. These cylinders, as well as refractory walls pressed against their flat lateral ends, define a casting space into which the liquid metal is continuously poured. This solidifies inside the grooves and in the circular cross-sections which they define to form filaments which are well detached from each other, whereas in principle solidification does not take place on the portions of the cylinders. which include insulating masses, flush or not. The presence of the insulating masses and the need to preferentially cool the grooves make the construction of the cylinders very complex. In addition, in practice, it is to be feared that, due to the erosion and deformations of the cylinders, their parts which should be permanently perfectly contiguous are not all entirely so. This could lead to dangerous uncontrolled exfiltration of liquid metal out of the casting space which would deteriorate the installation, as well as to the appearance of burrs on the filaments if these exfiltrations take place at the edges of the grooves.

The object of the invention is to provide producers of filiform metallic materials whose cross-section has dimensions ranging from approximately 0.5 to 25 mm, an installation enabling them to obtain reliably, directly from liquid metal, filaments whose cross section is close to that desired for the final material.

To this end, the subject of the invention is an installation for the continuous casting of metallic filaments directly from liquid metal, of the type comprising two internally cooled cylinders, having their longitudinal axes kept horizontal and provided with means for rotating them. in opposite directions around said axes, and the lateral surfaces of which include spaced grooves in which the solidification of said filaments takes place, two lateral faces applied against the planar ends of said cylinders so as to define, in cooperation with said cylinders, a space of laterally closed casting, and means for introducing molten metal inside said casting space, characterized in that the spaces separating said grooves are constituted by parts projecting from the nominal diameter of the cylinders, and in that each of said protruding parts of one of said cylinders penetrates inside a groove of the other cylinder, so as to partially fill it, a functional clearance being provided between said protruding part and the side walls of said groove.

As will have been understood, the invention consists in providing relatively deep grooves on each of the cylinders, into which project protruding parts formed on the surface of the other cylinder between its own grooves. The grooves and the projecting parts which penetrate there together define spaces in each of which takes place the solidification of a filament.

The invention will be better understood on reading the description which follows, given with reference to the following figures:

- Figure 1 which shows schematically, seen from above, a cylinder of the type used on the installation according to the invention;

- Figure 2 which shows schematically, top view, a casting installation 1 according to the invention;

- Figure 3 which shows a knife used to spread the rolled products after their solidification;

The casting cylinder 1 shown in FIG. 1 is particularly intended to constitute one of the essential elements of the installation according to the invention which will be described later. This cylinder 1 has a diameter D which will be called hereinafter "nominal diameter", and which corresponds at its actual diameter in the vicinity of its two planar ends 2, 3. It has axes 4, 5 intended to be engaged in conventional rotation means. Its lateral surface comprises a series of grooves 6-14 intended, as will be seen below, to constitute a series of ingot molds in each of which a metallic filament will solidify. In the example shown, these grooves have a section of substantially rectangular shape in the vicinity of the surface of the cylinder 1, while their deepest part has a semi-circular shape. The spaces separating these grooves 6-14 from one another are constituted by annular zones 15-23 of diameter D ', such that D ¹ is greater than the nominal diameter D of the cylinder 1. These annular zones 15-23 therefore constitute parts protruding (and will be designated below) with respect to the zones 24, 25 of the lateral surface of the cylinder 1 closest to the ends 2, 3 which have been said to have a diameter equal to D. These zones 24, 25 will be called "shores" below. The dimensions which the protrusions 15-23 must have will be defined below. The cylinder 1 is, at least for its outer part, made of a metal which is a good conductor of heat such as copper or a copper alloy. It is provided with conventional means (not shown) for energetically cooling its lateral surface from the inside, which must be ensured that they effectively contribute to cooling both the walls of the grooves 6-14 and those of the projecting parts 15 -23 and banks 24, 25.

The casting installation shown in FIG. 2 is essentially constituted by the union of two cylinders 1 and l of the previous type (the elements of cylinder l 'which correspond to those of cylinder 1 of FIG. 1 are designated by the same references to which we add a "'"). These cylinders 1 and l are nested one inside the other in such a way that:

the banks 24, 25 of the cylinder 1 are spaced from the corresponding banks 24 ', 25' of the cylinder l ', so as to define a space 26 between the banks 24 and 25', and a space 27 between the edges 24 'and 25, these spaces 26, 27 being a few mm wide and for example a few mm or a few cm long;

- the projecting parts 15-23 of the cylinder 1 penetrate into the grooves 6 '-14' of the cylinder l ', and the projecting parts 15'-23' of the cylinder penetrate it into the grooves 6-14 of the cylinder 1, so that, on the one hand, at the axes of the cylinders 1, the, the projecting portions 15-23, 15 '-23' and the bottom of the corresponding grooves 6-14, 6'-14 'are separated by a space 28-45 corresponding to the shape and dimensions of the filaments to be cast (18 in number in the example shown), and on the other hand, the side walls of the projecting parts 15-23, 15 '-23' and the side walls of the corresponding grooves 6-14, 6 '-14' are only separated by a functional clearance of the order of 1/10 mm for example, the dimensions of the projecting parts 15-23, 15'-23 '( in particular the diameter D ') and of the grooves 6-14, 6' -14 'must therefore be determined as a function of the satisfaction of these two conditions, also in conjunction with the width of the es paces 26, 27 separating the banks 24 and 25 ', 25' and 24 of the cylinders 1, l '.

The installation also includes two closing plates 46, 47 applied against the flat ends 2, 2 'and 3, 3' of the cylinders 1, l 'so as to define, in cooperation with the cylinders 1, l', a space for casting capable of containing liquid metal. Such a configuration is identical in principle to that which is used on installations for casting between two cylinders of thin metal strips. The installation finally comprises means not shown allowing the cylinders 1 to rotate in opposite directions, the around their respective axes, and means not shown allowing the continuous introduction of liquid steel into the casting space. defined by the cylinders 1, l 'and the closing plates 46, 47. These various means are similar to those used on installations for the continuous casting of thin strips between cylinders. The casting is carried out in a manner comparable to that practiced in the casting of thin metal strips between cylinders. Before its start, spaces 26, 27, 28-45 are closed. Then the cylinder cooling system is started and the molten metal is introduced into the casting space. Solidification then begins, against the edges 24, 25, in the grooves 6-14, 6'- 14 'and against the projecting parts 15-23, 15' -23 '. Finally, the rotation of the cylinders 1 is started, the while opening the spaces 26, 27, 28-45, so as to extract therefrom filaments during solidification having sections corresponding to those of said spaces 28-45. At the same time, strips are also extracted, the section of which corresponds to that of the spaces 26, 27. At the same time, the casting space is continuously supplied with liquid metal.

The filaments and bands thus formed are then optionally cooled, and are guided to winders.

The strips leaving the spaces 26, 27 are not necessarily to be considered as exploitable products. Their casting is only a direct consequence of the characteristic according to which the cylinders 1, l 'are not contiguous. This avoids the problems which would be linked to an undesired solidification which would initiate on the banks 24, 25, 24 ', 25' and which would tend to separate the cylinders 1, one from the other when the skins solidified would meet at the contact areas between the cylinders. The proposed configuration, with banks 24, 25, 24 ', 25' normally cooled and cylinders 1, the non-contiguous, allows and even requires that such solidification occurs on the banks 24, 25, 24 ', 25 '. It is simply necessary for it to be controlled in such a way that the resulting strips are sufficiently solidified on leaving the spaces 26, 27 so that their skins are not likely to tear and allow liquid metal to escape. It goes without saying that this condition also applies to the filaments leaving spaces 28-45. The different dimensional parameters (diameter D of the cylinders 1,1 ', number and diameter D' of the projecting parts 15-23, 15 '-23', number and depth of splines 6-14, 6'-14 ', width of edges 24, 25, 24', 25 ', width of spaces 26, 27, depth of the liquid metal bath in the casting space) and functional (rotation speed of cylinders 1, l ', cooling fluid flow in cylinders 1, l') are chosen so that these conditions are satisfied, and also according to the dimensions of the filaments that are wants to produce, the productivity that we want to give to the installation and the nature of the cast metal. It may be desirable that the solidification of the filaments and the lateral bands is not completed upstream of the neck (that is to say of the level where the cylinders 1, 1 'are closest to each other) . Otherwise, the cylinders 1, the should then exert a real rolling force on the strips and the filaments. This effort could be tolerated for the casting of relatively soft metals (tin, aluminum, copper), but, in the case of steel casting, would lead to having to build a plant capable of supporting this rolling effort, which would be a serious burden. its cost. In the case of steel, it is rather desirable that at the level of the neck, the core of the filaments is still in the pasty state, that is to say that it contains both solid metal and liquid metal, and thus still slightly compressible. In this way, under the effect of the progressive narrowing of the spaces 28-45 as one approaches the neck, the filaments in the course of solidification undergo a compressive force on the part of the projecting parts 15-23, 15'- 23 ', which limits the formation of porosities and segregations in their hearts. On the other hand, the projecting parts 15-23, 15'-23 'thus contribute to the entrainment and the extraction from the spaces 28-45 of the cast filaments.

In the example shown in Figures 1 and 2, the projecting parts 15-23, 15 '-23' have, at their end, a substantially rectilinear shape. In cooperation with the grooves 6-14, 6 '-14', they give the filaments an approximately semicircular section. If we want then obtain a filament of different section (for example strictly circular), a subsequent shaping step is necessary. As a variant, the ends of the protrusions 15-23, 15 '-23' can be given a concave shape, in order to bring the cross-section of the filaments closer to a circular section. A convex shape is not desirable, as this would encourage the infiltration of liquid metal between the side walls of the projections 15-23, 15'-23 'and the grooves 6-14, 6'-14', and therefore the appearance of burrs on the filaments. Such burrs could seriously damage the installations ensuring the subsequent shaping of the filaments. If it is desired to obtain finished products of more complex shape, it is also possible to give the grooves 6-14, 6 '-14' a shape different from that shown and closer to the final shape of the products.

It has been said that the cylinders are preferably made of copper or a copper alloy. For this purpose, it is possible to use a copper alloy with structural hardening, that is to say comprising within it a dispersion of oxides which limits its possibilities of thermal expansion. One can also provide for coating the cylinders 1, l 'with a layer of nickel 1 to 2 mm thick, in order to limit the thermal deformations of the surface of the cylinders 1, l' in contact with the liquid metal. This layer of nickel can be applied over the entire surface of the cylinders 1, l ', or only on the ends of the protrusions 15-23, 15'-23', or only on the grooves 6-14, 6 '-14' .

The dimensions of the section of the filaments thus cast can be very variable. They are of the order of 0.5 to 25 mm, preferably from 1 to 7 mm.

On leaving the spaces 26, 27, 28-45, the bands and the filaments may tend to remain integral with the grooves 6-14, 6 '-14'. Help must then be taken off, mainly at the start of casting, when they have not yet been gripped by the winders. For this purpose, knives of the type shown in FIG. 3 can be placed under each of the cylinders 1, 1 ". are in the form of a base plate 48 on which are attached two rectangular section strips 49, 50 and, arranged between these strips 49, 50, rods 51-59 whose external shape matches that of the grooves 6-14, 6'-14 '. The upper ends of the lamellae 49, 50 and of the rods 51-59 are cut in a bevel. Before casting, a knife 49 is placed under each cylinder 1, l ', the ends of the strips 49, 50 being in contact with the edges 24, 25 - 24', 25 'of the cylinders 1, l' and the ends of the rods 51 -59 being engaged in the grooves 6-14, 6 '-14', their bevelled parts being turned towards the casting space. In this way, when the strips and the filaments come into contact with the beveled ends of the lamellae 49, 50 and the rods 51-59, they are forced to leave the edges 24, 25, 24 ', 25' and the grooves 6-14 , 6 '-14', and can therefore be oriented towards the winders.

Alternatively, an alternation of grooves and projecting parts can be provided over the entire lateral surface of the cylinders 1, l '. This eliminates the edges 24, 24 ', 25, 25' of flat section and the spaces 26, 27 which separate them, as well as the casting of strips in these spaces 26, 27.

The invention applies to the casting of metallic filaments of all kinds, for example steel, aluminum, copper or tin. It has the advantage, compared to existing devices, of providing filaments in all circumstances perfectly separated from each other, free of burrs which should be removed before subsequent shaping, and having good internal health (free of porosity and poorly segregated at heart). The absence of contact zones between the cylinders 1 finally allows it to limit their wear.

Claims

1) Installation for continuous casting of metallic filaments directly from liquid metal, of the type comprising two cylinders (1,1 ') internally cooled, having their longitudinal axes kept horizontal and provided with means for rotating them in opposite directions around said axes, and whose lateral surfaces include grooves (6-14, 6 '-14') spaced in which is effected the solidification of said filaments, two lateral faces (46,47) applied against the planar ends (2, 3, 2 ', 3') of said cylinders (1,1 '), so as to define, in cooperation with said cylinders (1,1'), a pouring space closed laterally, and means for introducing liquid metal into the interior of said casting space, characterized in that the spaces separating said grooves are constituted by protruding parts (15-23, 15 '-23') relative to the nominal diameter (D) of the cylinders, and in that each of said partsprotrusions (15-23, 15 '-23') of one of said cylinders (1,1 ') penetrates inside a groove (6-14, 6' -14 ') of the other cylinder (1 , 1 '), so as to partially fill it, a functional clearance being provided between said projection (15-23, 15' -23 ') and the side walls of said groove (6-14, 6' -14 ') .

2) Installation according to claim 1, characterized in that it comprises, below said cylinders (1,1 '), means to assist the separation of said solidified filaments and said cylinders (1,1').

3) Installation according to claim 2, characterized in that said means for assisting the separation of said filaments and said cylinders (1,1 ') comprise rods (51,59) each having a beveled end penetrating into one of said grooves ( 6-14, 6 '-14'). 4) Installation according to one of claims 1 to 3, characterized in that said cylinders (1,1 ') are made of copper-based alloy.

5) Installation according to claim 4, characterized in that the ends of said projecting parts (15-23, 15 '-23') have a nickel coating.

6) Installation according to claim 4 or 5, characterized in that said grooves (6-14, 6 '-14') have a nickel coating.

7) Installation according to one of claims 1 to 6, characterized in that said cylinders (1,1 ') have edges (24, 24', 25, 25 ') of planar section, at which the diameter of the cylinder is equal to its nominal diameter (D), and in that two edges (24, 24 ', 25, 25') facing each other define a space (26,27) in cooperation with said lateral faces (46,47).