FR2673551A1 - METHOD AND DEVICE FOR CONTINUOUS CASTING LOW DIAMETER METAL WIRE DIRECTLY FROM LIQUID METAL - Google Patents

Abstract

The object of the invention is a process for the continuous casting of fine metal wire in which a jet of liquid metal emerging from the nozzle of a reservoir is quenched and solidified in a layer of cooling liquid, characterized in that said liquid flows over a cylindrical or slightly frustoconical fixed surface with a substantially vertical axis, in that the reservoir is imparted a rotational movement around the axis of said surface so as to cause the end of the nozzle to move on a circular path concentric with said surface, and in that the metal jet is ejected from the nozzle in a direction opposite to the direction of movement of the nozzle. The subject of the invention is also a device for implementing this method.

Description

METHOD AND DEVICE FOR CONTINUOUS CASTING OF METAL WIRE

  LOW DIAMETER DIRECTLY FROM LIQUID METAL

  The invention relates to the manufacture of small diameter metal wires by quenching a jet of liquid metal in

  a layer of cooling liquid.

  Recent years have seen the development of a casting process for obtaining, directly from liquid metal, metal filaments of indefinite length, substantially circular section and very small diameter, which can be as low as 80 Nom approximately , and to which one can confer an amorphous structure, if the composition of the metal lends itself to it and if the cooling conditions of the liquid metal are sufficiently violent (at least 1040 C / s). This process is described in particular in the European Patent EP 39169 It consists in forming a jet of metal from a liquid metal tank provided with heating means and an outlet nozzle whose diameter is

  equal to or slightly greater than the diameter of the desired filament.

  This metal jet then enters a layer of cooling liquid, such as water or an aqueous solution of a salt, which solidifies the jet into a metal wire. This layer of liquid is in motion in a direction transverse to that of the metal jet and flows on a solid surface itself in motion which drives the liquid, and may be constituted by the inside of a drum rotating about a horizontal axis (European Patent EP 39169 already cited ) or by a horizontal or concave portion of a looped groove forming a loop (European Patent EP 89134) The wire is entrained in the cooling liquid, which preferably moves laminarly at a speed substantially equal to or slightly greater than the speed ejection of the liquid metal jet out of the tank (of the order of 5 to 15 m / s) As it is poured, the wire is wound in the drum under the effect of the centrifugal force, or is continuously out of the cooling medium by appropriate means to be captured and possibly wound outside the casting machine. Thanks to the high cooling rate that it can provide, this process makes it possible, if the metal is amorphizable, to obtain amorphous son of uniform size having, among other properties, a very high tensile strength. amorphous son in alloys based on various metals such as iron, copper, cobalt, gold, aluminum, etc. The disadvantages of the devices implementing this method are however numerous The drums with horizontal axis of rotation do not allow not, in their simplest versions, to recover the wire in a continuous way and to drag it outside the installation, and to give itself this possibility leads to a very significant complication in the construction of the installation In all the case, the size of the tank is limited because it must fit inside the drum Except to exaggerate the diameter of the drum, which makes it difficult to coolant under the effect of centrifugal force, it is therefore hardly possible to treat

  only once amounts of metal exceeding a few kilograms.

  As for installations using grooved belts, they allow the use of liquid metal tanks of high capacity, but are very cumbersome Indeed the cooling liquid must generally run several meters on the strip after deposition before its turbulence is sufficiently dissipated to allow a

  regular solidification of the metal.

  A variant of this process, presented in Japanese Patent Application JP 60250859, consists in placing the cooling liquid in a fixed tank, in arranging the liquid metal tank above this tank, in orienting the outlet nozzle of the jet of liquid metal so that the latter enters the cooling liquid at an angle of not more than 30 È from its surface, and to print to the tank a rotational movement about a vertical axis not passing through the nozzle The output thus describes a circular path above the tray, and the solidified wire is deposited at the bottom of the tray in the form of superimposed turns It is however not possible to

  recover the thread continuously.

  The object of the invention is to provide a yarn casting process that allows continuous yarn collection and does not limit the amount of metal that can be processed at one time to a value that is too small. a

  simple design device for its implementation.

  To this end, the subject of the invention is a process for continuous casting of fine wire in which a jet of liquid metal coming out of the nozzle of a tank is quenched and solidified in a layer of cooling liquid, characterized in that said fluid flows on a cylindrical or slightly frustoconical fixed surface with a substantially vertical axis, in that a rotation movement is imparted to the reservoir about the axis of said surface so as to move the end of the nozzle on a concentric circular path to said surface, and in that the metal jet is ejected from the nozzle in a direction at right angles or obtuse with the tangent of the circular path. The invention also relates to a device for continuous casting of fine wire comprising a reservoir containing a liquid metal provided with a nozzle, through which flows a jet of said liquid metal, oriented towards a layer of cooling liquid wherein said jet is quenched and solidified in the form of a wire, characterized in that it comprises a cylindrical or slightly frustoconical fixed surface of substantially vertical axis over which said layer of cooling liquid flows, means for printing said reservoir a rotational movement about the axis of said surface, and means for collecting said wire as and when it is formed, placed in

below said surface.

  As will be understood, the invention consists in realizing the solidification of the jet of liquid metal in a film of cooling liquid freely flowing over a cylindrical or slightly frustoconical surface. The solidified wire thus descends progressively along this surface in the form of turns. , and, below the surface, is seized

  by a device for evacuating it.

  The invention will be better understood on reading the

  following description, referring to the single figure

  annexed, showing the installation seen in frontal section and in perspective. In the yarn casting installation as shown in the single figure, the cooling medium in which the quenching and solidification of the liquid metal M is carried out consists of a layer of liquid 1 dripping at a speed v on the upper surface. 2 This support has any general shape, for example cylindrical as shown. Its essential characteristic is to have, in its central part, a recess 4 passing through it from one side to the other, and made in such a way that the surface 5 of the support 3 delimiting this recess is cylindrical, having a vertical axis XY. The liquid 1 flows from the upper surface 2 of the support onto the cylindrical surface 5 and forms

  and a layer of thickness e flowing at a speed v '.

  The junction between the upper surface 2 of the support and the cylindrical surface 5 of the recess is preferably effected without a sharp angle, in order to minimize the disturbances brought to the flow of the liquid 1 by the rupture of the slope. The liquid 1 is brought on the support 3 by means such as a shell 6 hollow connected to a liquid supply not shown This ferrule has an orifice 7 through which the liquid flows This orifice describes a substantially concentric circle to the recess 4 Its dimensions and that the flow rate of the liquid are calculated so as to form a liquid layer 1 of regular thickness e of the order of 1 cm, and with a relatively low velocity v 'in the recess 4 to avoid that s' create too much turbulence inside

of layer 1.

2673551

  Above the recess 4 is a reservoir 8 containing the liquid metal M This reservoir has a symmetry of revolution with respect to the axis XY, and may for example have a generally cylindrical shape as shown It is coated internally with a refractory layer which is not very reactive with respect to the metal M, or is itself entirely in this refractory It is equipped with heating means, such as an induction coil 9, the power supply of which is not These heating means make it possible to maintain at the desired level the temperature of the liquid metal M which has previously been

  introduced into the tank, or even to ensure

  The tank 8 also comprises means 10 for rotating it around the XY axis at an angular velocity W, and means 11 for introducing a neutral gas into its interior. it makes it possible to protect the liquid metal M against the atmospheric oxidation It also makes it possible to pressurize the reservoir so as to favor the ejection of the liquid metal and to regulate its output flow independently of the

  amount of metal remaining inside the tank 8.

  This outlet of the liquid metal from the reservoir 8 is effected by a nozzle 12 placed in the bottom 13 of the reservoir. This nozzle 12 must fulfill the following conditions: its terminal diameter is equal to or slightly greater than the desired diameter for the wire 14, that is 80 to 200 μm, to form a coherent liquid metal jet having this diameter; it must direct the jet of liquid metal to the coolant layer 1 dripping on the cylindrical surface 5, and in a direction opposite to the direction of movement of the nozzle; for example, if, as shown in the figure, the rotation of the reservoir is carried out counterclockwise, the end of the nozzle 12 must be oriented towards the rear of the cutting plane; its end must be located at a very short distance (of the order of 1 to a few mm) from the surface of the cooling liquid layer 1, to ensure good coherence of the metal jet 15 at the time of its penetration into the

the liquid.

  Usually, in direct wire casting installations, the cooling liquid is set in motion while the reservoir is fixed, but the speed Vf of the liquid metal jet, which is also the speed of the solidified wire, is made the velocity Vl of the liquid is equal, or that Vl is slightly greater than Vf, in a ratio not exceeding 1.3 to 1.5 If Vf is greater than Vl, the jet and the wire are not entrained by the liquid, and there is an accumulation effect which results in an irregular wire thickness If, on the contrary, Vl is much greater than Vf, the jet drive effect is too great and leads to its periodic failure, which makes it impossible to Obtaining a continuous wire of great length In the installation according to the invention, it is possible to neglect the falling speed v 'of the cooling liquid layer 1 and to admit that it is fixed. The ratio of the speeds to be taken in consideration for adjustment of the installation is therefore the ratio between the speed of the metal jet 15 and the wire 14, and the linear speed Vb of the end of the nozzle 12, equal to V R if R is the distance between the end of the nozzle These speeds are, for example, of the order of 5 to 15 m / s, as in conventional installations, and must be sufficient to guarantee a high solidification rate, especially if the ratio Vb is also within the range of 1 to 1.5, the direction of penetration of the jet 15 into the cooling liquid 1 must also be optimized, as in conventional installations, where tilt of the jet with respect to the surface of the liquid is very variable In this optimization, it may be necessary to take into account the falling speed v 'of

  the cooling liquid layer 1.

  To constitute this layer 1, any liquid known for its cooling capacities can be used, for example

  water, saline aqueous solutions, or liquefied gases.

  Under the effect of the centrifugal force and the direction initially imposed on the metal jet 15, the solidified wire 14 is pressed against the cylindrical surface 5 under the effect of its weight and the thrust exerted on it by the layer descending cooling liquid 1, the wire progressively descends along the surface 5 and thus forms turns Under the support 3, these turns fall on each other and are deposited on a conveyor belt 16 moved by means symbolized by a pulley 17 and which evacuates the turns of yarn as and when they are formed, the installation may also comprise means (not shown) for collecting the spent coolant and returning this liquid in the feed circuit of In contrast to the usual solution of using a fixed reservoir and a layer of liquid deposited on a moving surface, an advantage of the invention is to cause centrifugation of the This centrifugation accentuates the separation between the metal and the nonmetallic inclusions which it inevitably contains, and which ultimately return to the surface of the metal M to form a slag layer. and the quality of the wire, while reducing the risk of clogging the nozzle 12 by the inclusions Another advantage of this installation is that the metal tank 8 is not limited in size in the direction of the height It is therefore possible to treat at a single time a quantity of metal as large as desired, provided to provide means for rotating the reservoir of a suitable power Finally, the solidified wire leaves of itself the solidification zone in the form of turns, and its evacuation and winding do not require complex installation For this purpose, instead of a conveyor belt, it can be provided a descending plateau gradually or all t another means of capturing

  the end of the wire and wind it on a mandrel.

  Alternatively, the surface 5 of the recess may not

  to be rigorously cylindrical, but slightly frustoconical.

  Such a form allows better guiding and better formation of the turns, and makes it possible to reduce the velocity v 'of the liquid layer 1, for a speed v equal to the exit of the ferrule. Thus, the solidification conditions are approached more closely. In addition, the distance between the nozzle 12 and the surface of the liquid layer 1 can be adjusted by simply translating the reservoir 8 vertically. However, the conicity of the surface 5 should not be important to interfere with the descent of the turns of wire that could become trapped inside the recess, which

  would oblige to interrupt the casting.

  Similarly, it is possible to feed the metal tank 8 continuously, either with already liquid metal or with solid metal divided so finely that its complete melting occurs before it reaches the nozzle 12. thus further reducing the limit of the amount of thread that can be cast in a single operation It is also possible to equip the tank 8 with several adjacent nozzles for casting multi-strand wires, in a manner similar to that described in the document JP 63273554 Finally, it is possible, in known manner, to move the end of the nozzle 12 away from the liquid layer 1 by more than a few millimeters, if it is possible to artificially maintain the consistency of the metal jet. creating, on the surface of the jet, in a known manner, an oxide film, thanks to the limited oxidation of one of the components of the metal by air or by an appropriate oxidizing atmosphere, as described, for example, in

EP 360104.

  The invention is applicable to the casting of small diameter metal wires, for example made of steel, and makes it possible to obtain son of amorphous structure if the solidification conditions are sufficiently violent and if the

  composition of cast metal lends itself to it.

9 2673551

Claims (5)

  1) Process for continuous casting of fine wire in which a jet of liquid metal leaving the nozzle of a tank is hardened and solidified in a layer of cooling liquid, characterized in that said liquid flows on a fixed cylindrical surface or slightly frustoconical axis of substantially vertical axis, in that one prints to the tank a rotational movement about the axis of said surface so as to move the end of the nozzle on a circular path concentric to said surface, and that the metal jet is ejected from the nozzle in a direction opposite to the direction of moving the nozzle.   2) Process according to claim 1, characterized in that the linear speed of displacement Vb of the end of the nozzle and the speed Vf of the metal jet leaving the nozzle are in a ratio Vb of between 1 and about 1.5 vf 3) device for continuous casting of fine wire comprising a reservoir (8) containing a liquid metal (M) provided with a nozzle (12) through which flows a jet (15) of said liquid metal (M) oriented in the direction a cooling liquid layer (1) in which said jet (15) is hardened and solidified in the form of a wire (14), characterized in that it comprises a cylindrical or slightly frustoconical fixed suirface (5) of substantially vertical axis (XY) over which said layer (1) of coolant flows, means (10) for printing said reservoir (8) a rotational movement about the axis (XY) of said surface, and means for collect said wire (14) as it is formed, placed below said surface (5). 2673551   4) Device according to claim 3, characterized in that said means for collecting the wire (14)   are constituted by a progressively descending plateau.   5) Device according to claim 3, characterized in that said means for collecting the wire are   constituted by a conveyor belt (16).