Device for treating molten metal comprising a smooth rotatable ladle and a stationary stirring arm

Abstract

The invention relates to a device for treating molten metal, the device comprising a ladle defining an internal volume intended to contain the molten metal, and means for rotating the ladle about an axis of rotation. According to the invention, the ladle comprises an inner peripheral wall and an inner bottom wall that are substantially smooth, and the device comprises at least one stirring arm capable of assuming a stirring position in which it is at least partially immersed in the internal volume of the ladle and in which it is stationary with respect to the ladle.

Description

[0001] DESCRIPTION

[0002] Title: Device for processing molten metal comprising a smooth rotating ladle and a stationary mixing arm

[0003] 1. Scope of the invention

[0004] The field of the invention is that of the treatment of molten metals, in particular cast irons or any other alloy such as ferrous alloys, copper alloys, light alloys or others.

[0005] The invention relates more particularly to devices used to ensure, at least partially, the processing of such materials, more particularly to the pockets used for this purpose.

[0006] 2. Prior art

[0007] In the field of metallurgy, it is common to produce metal parts by casting. To do this, a furnace is used to melt a metal or a metal alloy. The molten metal then undergoes a series of treatments before being poured into a mold. These treatments include desulfurization, nucleation (i.e., germination), nodularization, and inoculation.

[0008] Each treatment the molten metal undergoes between leaving the furnace and being poured into a mold is carried out in a specific treatment ladle. Thus, according to prior art, as many treatment ladles are used as the metal requires treatment. For example, if the molten metal requires four treatments—desulfurization, initialization, nodularization, and inoculation—between leaving the furnace and being poured into a mold, at least four treatment ladles will be used, each dedicated to one of the treatments.

[0009] This leads to a multiplication of the number of pockets implemented and therefore to an increase in the cost of processing equipment as well as its bulk.

[0010] Furthermore, the various treatments require the injection of at least one reagent into the molten metal contained in the ladles. The ladles are static, so the reagent is assumed to mix with the molten metal, either on its own or during transfer. This can mean that the reagent is not perfectly mixed with the molten metal, or that it is necessary to leave the reagent in contact with the molten metal for a long time to ensure sufficient mixing.

[0011] This tends to impair the productivity of treatments and / or their quality.

[0012] To remedy this, and in particular to optimize the mixing of molten metal and at least one reagent injected into a mixing bag, the Applicant designed a rotating mixing bag.

[0013] Such a ladle, which is described in the international patent application bearing the number WO-A1-2024 / 068775, comprises a ladle defining an internal volume suitable for containing molten metal and at least one reagent, and means for driving this ladle in rotation along at least one axis of rotation, in practice along an essentially vertical axis of rotation.

[0014] This pocket includes a peripheral inner surface with blades projecting towards the center of the pocket. The bottom may also have blades projecting towards the center of the pocket.

[0015] The implementation of these blades inside the ladle greatly optimizes the mixing of the reagents injected into the molten metal contained in the ladle when it is animated by a rotational movement.

[0016] However, this technique has some drawbacks.

[0017] Firstly, this technique is not suitable for large ladles (especially those with a capacity exceeding 2 tonnes), and therefore only allows the processing of a "small" quantity of molten metal.

[0018] Secondly, this technique poses maintenance problems because the blades tend to get dirty and deteriorate, requiring time-consuming and costly maintenance campaigns that lead to a loss of productivity.

[0019] Finally, to obtain satisfactory mixing results, these bags require successive acceleration / deceleration / stopping, with reversal of the direction of rotation upon restart, which is complex to achieve and tends to accelerate wear on the bag's drive and rotation guidance systems.

[0020] Therefore, rotary mixing bags with integrated blades, although offering many advantages, can still be improved.

[0021] 3. Objectives of the invention

[0022] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0023] In particular, according to at least one embodiment, an objective of the invention is to provide a molten metal mixing pouch that improves the mixing of the metal with at least one reagent injected into the pouch. Specifically, the invention aims, according to at least one embodiment, to provide such a pouch that allows the processing of a significant quantity of metal, in particular exceeding 2 tonnes.

[0024] Another objective of the invention is, according to at least one embodiment, to provide such a pocket which requires little maintenance.

[0025] In particular, the invention aims, according to at least one embodiment, to provide such a pocket which is not subject to fouling.

[0026] Another objective of the invention is, according to at least one embodiment, to provide such a pouch which is easy to implement in the sense that it does not require, in order to obtain a satisfactory mixture, to be successively accelerated and decelerated and to undergo reversals of its direction of rotation.

[0027] Another objective of the invention is, according to at least one embodiment, to provide such a pouch which is reliable and / or robust and / or simple in design and / or versatile and / or contributes to improving efficiency.

[0028] 4. Presentation of the invention

[0029] All or part of these objectives, as well as others which will appear subsequently, are achieved by means of a device for processing a molten metal, said device comprising a ladle defining an internal volume intended to contain said molten metal, and means for driving said ladle in rotation along an axis of rotation.

[0030] According to the invention, said pouch comprises an essentially smooth inner peripheral wall and bottom wall and in that said device comprises at least one mixing arm capable of assuming a mixing position in which it is at least partially immersed in said inner volume of said pouch and in which it is fixed relative to said pouch.

[0031] Thus, the invention consists of immersing, in a tank with a smooth inner wall, a mixing arm which can be kept stationary relative to the tank when it is animated by a rotational movement to proceed with the mixing of molten metal and reagents which it contains.

[0032] This implementation allows, in particular: obtaining an optimal mixture of reactant(s) in the molten metal contained in the ladle; treating a large quantity of metal in the ladle, in particular more than 2 tonnes; carrying out a treatment with a single direction of rotation and at a substantially constant speed without requiring reversing the direction of rotation of the ladle and accelerating / decelerating the ladle; inducing few maintenance campaigns due to the elimination of the mixing blades on the internal faces of the ladle, which tend to become clogged in the solutions of the prior art; obtaining better productivity; offering a simple and robust technique; lowering maintenance and production costs.

[0033] According to one possible characteristic, said mixing arm has a quadrangular cross-section in a plane orthogonal to said axis of rotation of said pouch.

[0034] According to one possible characteristic, said mixing arm has a rectangular cross-section in a plane orthogonal to said axis of rotation of said pouch, the largest dimension of said rectangular section extending in the direction of said axis of rotation of said pouch.

[0035] According to one possible feature, said mixing arm includes a lateral face oriented towards and distant from said inner peripheral wall of said pocket.

[0036] According to one possible feature, said mixing arm includes a lower face oriented towards and distant from said inner bottom wall of said pocket.

[0037] According to one possible characteristic, said mixing arm is laterally offset from a diametrical plane of said pouch passing through the axis of rotation of said pouch.

[0038] According to one possible characteristic, said mixing arm includes a median plane coinciding with a diametral plane of said pouch passing through the axis of rotation of said pouch.

[0039] According to one possible feature, said mixing arm is movable between: said mixing position, and a storage position in which it extends outside said internal volume delimited by said pocket.

[0040] According to one possible feature, a device according to the invention includes means for driving said mixing arm from one of its positions to another.

[0041] According to one possible feature, a device according to the invention includes means for driving said mixing arm in a plane containing said axis of rotation of said pouch or in a plane parallel to a plane containing said axis of rotation of said pouch, said drive means being capable of moving said mixing arm when it is in its mixing position.

[0042] 5. Description of the figures

[0043] Other features and advantages of the invention will become apparent from the following description of particular embodiments, given by way of simple illustrative and non-limiting examples, and the accompanying drawings, among which:

[0044] [Fig 1] Figure 1 illustrates a perspective view of a device according to the invention whose mixing arm is in the storage position;

[0045] [Fig 2] Figure 2 illustrates a perspective view of a device according to the invention whose mixing arm is in the mixing position;

[0046] [Fig 3] Figure 3 illustrates a cross-sectional view of a pocket of a device according to the invention along the diametrical plane passing through its axis of rotation;

[0047] [Fig 4] Figure 4 illustrates a perspective view of a mixing arm of a device according to the invention with a rectangular cross-section;

[0048] [Fig 5] [Fig 6] Figures 5 and 6 illustrate schematic views of the positioning of a mixing arm in a pocket of a device according to the invention.

[0049] 6. Description of specific embodiments

[0050] 6.1. Device

[0051] 6.1.1. General Structure

[0052] An example of a processing device according to the invention is presented in relation to figures 1 to 6.

[0053] Such a device includes a pocket 1. In the field of metallurgy, such a pocket 1 is sometimes referred to by the following names depending on the context in which it is used:

[0054] - transfer pouch;

[0055] - pouring ladle;

[0056] - treatment bag;

[0057] - mixing bag.

[0058] For the sake of simplicity, we will use here the term pocket which can indifferently perform at least the functions of at least the types of pockets mentioned above.

[0059] In this embodiment, this pocket 1 is in the form of a cylinder with a peripheral outer wall 10 and a bottom outer wall 11.

[0060] The bag 1 is open, at the end opposite the bottom 11, by a top opening 12. This top opening 12 may have one or more spouts 13. The top opening 12 of the bag 1 can be closed by means of a removable lid 2.

[0061] The removable lid 2 itself has an opening 20 leading into pocket 1.

[0062] The pocket 1 comprises an inner peripheral wall 100 and an inner bottom wall 110, which delimit an internal volume 14 suitable for containing molten metal.

[0063] Molten metal refers to a metal or an alloy of metals. Molten metal can be, for example, cast iron, a ferrous alloy, a light alloy, a copper alloy, or any other alloy or metal.

[0064] The inner peripheral wall 100 and the inner bottom wall 110 are essentially smooth. In other words, they do not have mixing fins protruding towards the center of the pouch, as is the case with the known solution described earlier in the section devoted to prior art. Of course, these walls may nevertheless have surface irregularities resulting, for example, from the process used to manufacture the pouch.

[0065] The device includes means for rotating the pouch 1 around an axis of rotation relative to a platform P on which it rests. This axis of rotation is substantially coincident with the longitudinal axis A of the pouch 1 and extends predominantly vertically, although it could be inclined.

[0066] The device also includes control means 4 for the rotation drive means 3, which allow in particular the programming of the rotation frequency of the pouch 1, its direction of rotation, the duration of the rotation cycles...

[0067] These means of rotational drive 3 and control 4 are not described in more detail here and may for example be of the type of those described in patent application WO-A1 -2024 / 068775.

[0068] The device includes a mixing arm 5. Here, a single mixing arm 5 is implemented. However, in variants, several mixing arms 5 may be implemented. In this case, they will preferably be distributed uniformly around the axis of rotation A of the pouch 1.

[0069] This mixing arm 5 is mounted movable relative to the platform P and the pouch between at least two positions, namely:

[0070] - a storage position, illustrated in Figure 1, in which it extends outside the internal volume 14 delimited by pocket 1, and

[0071] - a mixing position, illustrated in Figure 2, in which it is at least partially immersed inside the internal volume 14 delimited by the pouch 1, and remains motionless in rotation relative to the pouch when the pouch rotates around its axis of rotation relative to the arm.

[0072] The device includes drive means 6 for the mixing arm 5. These drive means 6 allow the mixing arm 5 to be moved from one of its positions to another.

[0073] These drive means can also optionally allow, from time to time during treatment, the mixing arm to be moved in a plane containing the axis of rotation of the bag or in a plane parallel to a plane containing the axis of rotation of the bag. Alternatively, specific drive means (i.e., different from the drive means for the mixing arm from one position to another) can perform this function.

[0074] These training means 6 here include a mast 60, which extends essentially vertically. This mast 60 is fixedly attached to the platform P. They also include beams 61, which are connected, at one of their ends, to the mast 60 by pivot joints 62 with axes essentially orthogonal to the mast 60. These beams 61 are fixed, at their other ends, to a mixer arm support 63 to which they are connected by pivot joints 64 with axes essentially orthogonal to the mast 60.

[0075] The mixing arm 5 is fixedly connected to the support 63, which extends essentially parallel to the mast 60.

[0076] The drive means 6 include a motor 65 connected to the beams 61, by a transmission T configured to transform a rapid rotation of the rotor of the motor 65:

[0077] - in a rotational movement of the beams 61 around the axes of the pivot joints 62 relative to the mast 60, and

[0078] - in a rotational movement of the beams 61 around the axes of the pivot joints 64 relative to the support 63. This transformation of movements results in a displacement of the mixing arm 5 from its storage position to its mixing position, and vice versa. During these displacements, the mixing arm 5 remains essentially parallel to the mast 60, and to the axis of rotation A of the pouch 1.

[0079] The transmission T, which connects the motor rotor 65 to the beams 61, includes for example a worm gear system.

[0080] 6.1.2. Mixing arm

[0081] The mixing arm 5 may have a quadrangular cross-section in a plane orthogonal to the axis of rotation A of the pocket 1.

[0082] In this case, the mixing arm 5 preferably has a rectangular cross-section in a plane orthogonal to the axis of rotation A of the pocket 1, with sides L x I. However, in a variant, its section may be square or otherwise.

[0083] The mixing arm 5 then comprises, in addition to its upper faces 55 and lower faces 54, four lateral faces, namely:

[0084] - a first face 50 oriented towards the inner peripheral wall 100 of the pocket 1;

[0085] - a second face 51 oriented towards the axis of rotation A of pocket 1;

[0086] - a third face 52 of junction between faces 50, 51, essentially orthogonal to them;

[0087] - a fourth face 53 of junction between faces 50, 51, essentially orthogonal to them.

[0088] When its section is rectangular, the largest dimension L of the rectangular section of the mixing arm 5 extends from the inner peripheral wall 100 of the pocket 1 in the direction of the axis of rotation A of the pocket 1.

[0089] The length L will preferably be between 25 and 40% of the inner radius of the pocket, and even more preferably around 1 / 3 of the inner radius of the pocket.

[0090] The length I will preferably be between 30 and 50% of the value of L.

[0091] 6.1.3. Arrangement of the mixing arm inside the bag in its mixing position

[0092] The first lateral face 50 of the mixing arm 5, facing the inner peripheral wall 100 of the ladle 1, is located a distance XB from it. This distance XB will be determined experimentally to optimize the flow within the rotating ladle. This distance XB will preferably be between 1 and 20% of the inner radius of the ladle. The lower face 54 of the mixing arm 5 is located a distance ZB from the inner bottom wall of the ladle. This distance ZB will be determined experimentally to optimize the flow within the rotating ladle. This distance ZB will preferably be between 25 and 40% of the height of the molten metal contained within the ladle.

[0093] Pocket 1 has a median or diametrical plane P passing through its axis of rotation A.

[0094] One of the junction faces 52, 53 between the first 50 and second 51 faces can be distant from the plane P by a distance YB.

[0095] The offset will be chosen such that, when the ladle 1 is set in motion to rotate about its axis A, the molten metal in the ladle 1 strikes the mixing arm 5 by its junction face furthest from the median plane P. In other words, the direction of rotation of the ladle 1 will be from the junction face furthest from the plane P towards the junction face closest to the plane P.

[0096] This distance YB will be determined experimentally to optimize the flow within the rotating pouch. This distance YB will preferably be between 0 and 20% of the pouch's inner radius.

[0097] In one variant, the median plane of the mixing arm 5 may pass through the axis of rotation A of the pouch 1.

[0098] 6.2. Operation

[0099] 6.2.1. General Operation

[0100] To mix at least one reagent, such as grains of processing products and / or alloying element, with molten metal contained in the ladle, the following procedure can be followed.

[0101] Molten metal is introduced into ladle 1.

[0102] The mixing arm 5 is placed in its mixing position.

[0103] The pouch 1 is driven in rotation around its axis A of rotation. Such a pouch 1 preferentially operates at a constant rotational speed without requiring successive accelerations / decelerations / stops and without reversing its direction of rotation.

[0104] The mixing arm, in its mixing position, remains stationary in rotation relative to the bag while the bag, animated by a rotational movement, rotates around its axis relative to the mixing arm.

[0105] However, in practice, the mixing arm is occasionally moved, often in a back-and-forth motion, along the radius of the ladle, or more generally in a plane containing the ladle's axis of rotation or in a plane parallel to a plane containing the ladle's axis of rotation, all while the ladle is rotating. This prevents the establishment of a stable streamline within the ladle. Such stability would create dead zones on the surface of the molten bath where grains of processing products and / or alloying elements tend to stagnate, hindering the proper mixing of these elements with the molten metal.

[0106] Reagent is injected into pocket 1 at the surface of the molten metal.

[0107] 6.2.2. Effect of the mixing arm

[0108] The use of a mixing arm 5 induces a mixing of the reagent particles, initially located on the surface of the molten metal, from top to bottom of the ladle. More precisely, these particles, under the effect of the ladle's rotation, descend to a central region of the ladle and then rise to a peripheral region of the ladle.

[0109] 6.3. Advantages

[0110] The combined implementation of a rotating ladle with smooth inner walls and a stationary mixing arm rotating relative to the ladle while the ladle rotates around its axis of rotation provides numerous advantages, including: obtaining optimal mixing of reactant(s) in the molten metal contained in the ladle; the possibility of processing a large quantity of metal in the ladle, particularly exceeding 2 tonnes; processing feasible in a single direction of rotation and at a substantially constant speed without requiring reversing the direction of rotation of the ladle or accelerating / decelerating the ladle; fewer maintenance campaigns due to the elimination of mixing blades on the inner faces of the ladle, which tend to become clogged in prior art solutions; improved productivity; a simple and robust technique; and reduced maintenance and production costs.The mixing of the liquid alloy with the additive is carried out without the formation of a deep central vortex, which would cause some of the liquid alloy to be projected out of the ladle as the liquid alloy level rises at the periphery of the ladle. Mixing is instead ensured by the formation of small, successive vortices that form behind the mixing arm throughout the mixing process. These small vortices then disperse uniformly throughout the entire volume of the rotating ladle without causing the liquid alloy level to rise at the periphery of the ladle. Avoiding the deep central vortex ensures safe processing and allows the ladle to be used at its full capacity.

Claims

DEMANDS 1. Device for processing a molten metal, said device comprising a ladle (1) defining an internal volume (14) intended to contain said molten metal, and means for rotating said ladle (1) about an axis of rotation, characterized in that said ladle (1) comprises a smooth internal peripheral wall (100) and bottom wall (110) and in that said device comprises at least one mixing arm (5) capable of assuming a mixing position in which it is at least partially immersed in said internal volume (14) of said ladle (1) and in which it remains stationary in rotation while said ladle (1) rotates about its axis of rotation relative to said mixing arm (5).

2. Device according to claim 1 in which said mixing arm (5) has a quadrangular cross-section in a plane orthogonal to said axis of rotation of said pouch (1).

3. Device according to claim 2 in which said mixing arm (5) has a rectangular cross-section in a plane orthogonal to said axis of rotation of said pouch (1), the largest dimension of said rectangular section extending in the direction of said axis of rotation of said pouch (1).

4. Device according to any one of claims 1 to 3 in which said mixing arm (5) comprises a lateral face (50) oriented towards the side of said inner peripheral wall (100) of said pocket (1) and distant from it.

5. Device according to any one of claims 1 to 4 in which said mixing arm (5) comprises a lower face (54) oriented towards the side of said bottom wall (11a) inside said pocket (1) and distant from it.

6. Device according to any one of claims 1 to 5 in which said mixing arm (5) is laterally offset from a diametrical plane of said pouch (1) passing through the axis of rotation of said pouch (1).

7. Device according to any one of claims 1 to 6 in which said mixing arm (5) comprises a median plane coinciding with a diametral plane of said pouch (1) passing through the axis of rotation of said pouch (1).

8. Device according to any one of claims 1 to 7 in which said mixing arm (5) is movable between: said mixing position, and a storage position in which it extends outside said internal volume (1') delimited by said pocket (1).

9. Device according to claim 8 comprising means for driving said mixing arm (5) from one of its positions to another.

10. A device according to any one of claims 1 to 9 comprising means (6) for occasionally driving said mixing arm (5) in a reciprocating motion in a plane containing said axis of rotation of said pouch (1) or in a plane parallel to a plane containing said axis of rotation of said pouch (1), said drive means being capable of moving said mixing arm (5) when it is in its mixing position while said pouch (1) is rotating.

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