A molten metal processing device comprising a smooth rotating ladle and a stationary mixing arm

Abstract

The invention relates to a device for processing molten metal, said device comprising a ladle defining an internal volume for containing said molten metal, and means for rotating said ladle about an axis of rotation. According to the invention, said ladle comprises a peripheral wall and an internal bottom wall that are essentially smooth, and said device comprises at least one mixing arm capable of assuming a mixing position in which it is at least partially immersed in said internal volume of said ladle and in which it is fixed relative to said ladle (Fig. 2).

Description

Title of the invention: Device for processing molten metal comprising a smooth rotating ladle and a stationary mixing arm. 1. Scope of the invention

[0001] 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.

[0002] The invention relates more particularly to devices implemented to ensure, at least partially, the processing of such materials, more particularly to the pockets implemented for this purpose. 2. Prior art

[0003] 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, in particular, desulfurization, nucleation, nodularization, and inoculation.

[0004] Each of the treatments undergone by the molten metal between its removal from the furnace and its pouring into a mold is carried out in a specific treatment ladle. Thus, according to the prior art, as many treatment ladles are used as the metal requires treatments. For example, if the molten metal requires four treatments—i.e., desulfurization, initialization, nodularization, and inoculation—between its removal from the furnace and its pouring into a mold, at least four treatment ladles will be used, each dedicated to one of the treatments.

[0005] This leads to multiplying the number of pockets implemented and therefore increasing the cost of processing tools as well as their size.

[0006] 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, either on its own or during transfer, with the molten metal. This may 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.

[0007] This tends to impair the productivity of the treatments and / or their quality.

[0008] To remedy this, and in particular to optimize the mixing of the molten metal and at least one reagent injected into a mixing bag, the Applicant has designed a rotating mixing bag.

[0009] 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 the 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.

[0010] This pocket comprises a peripheral inner surface having blades projecting towards the center of the pocket. The bottom may also have blades projecting towards the center of the pocket.

[0011] The implementation of these blades inside the ladle makes it possible to greatly optimize the mixing of the reagents injected into the molten metal contained in the ladle when the latter is animated by a rotational movement.

[0012] However, this technique has some drawbacks.

[0013] Firstly, this technique is not suitable for large ladles (in particular those with a capacity exceeding 2 tonnes), and therefore only allows the processing of a "small" quantity of molten metal.

[0014] Secondly, this technique poses maintenance problems because the blades tend to get dirty and deteriorate, which requires time-consuming and costly maintenance campaigns leading to a loss of productivity.

[0015] Finally, in order to obtain satisfactory results in terms of mixing, these bags require successively to be accelerated / decelerated / stopped, with reversal of the direction of rotation upon restart, which is complex to achieve and tends to accelerate the wear of the drive and rotation guidance means of the bag.

[0016] Therefore, rotary mixing bags with integrated blades, although having many advantages, can still be improved. 3. Objectives of the invention

[0017] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0018] In particular, according to at least one embodiment, an objective of the invention is to provide a molten metal mixing pouch enabling the metal to be mixed more effectively with at least one reagent injected into the pouch.

[0019] In particular, the invention aims, according to at least one embodiment, to provide such a pouch which allows the processing of a large quantity of metal, in particular more than 2 tonnes.

[0020] Another objective of the invention is, according to at least one embodiment, to provide such a pocket which requires little maintenance.

[0021] In particular, the invention aims, according to at least one embodiment, to provide such a pocket which is not subject to fouling.

[0022] 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.

[0023] 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. 4. Presentation of the invention

[0024] 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.

[0025] 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.

[0026] Thus, the invention consists of immersing, in a tank with a smooth inner wall, a mixing arm which can be kept immobile 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.

[0027] This implementation notably allows: - to obtain an optimal mixture of reactant(s) in the molten metal contained in the ladle; - to process a significant quantity of metal in the ladle, in particular more than 2 tonnes; - to perform a treatment with a single direction of rotation and at a substantially constant speed without requiring reversal of the direction of rotation of the bag and acceleration / deceleration of the bag; - to induce few maintenance campaigns due to the removal of the mixing blades on the internal faces of the bag, which tend to get clogged in the solutions of the prior art; - to achieve better productivity; - to propose a simple and robust technique; - to lower maintenance and production costs.

[0028] According to one possible feature, said mixing arm has a quadrangular cross-section in a plane orthogonal to said axis of rotation of said pouch.

[0029] According to one possible feature, 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.

[0030] According to one possible feature, said mixing arm includes a lateral face oriented towards the side of said inner peripheral wall of said pocket and distant from it.

[0031] According to one possible feature, said mixing arm includes a lower face oriented towards the side of said inner bottom wall of said pocket and distant from it.

[0032] According to one possible feature, said mixing arm is laterally offset from a diametrical plane of said pouch passing through the axis of rotation of said pouch.

[0033] According to one possible feature, said mixing arm includes a median plane coinciding with a diametrical plane of said pouch passing through the axis of rotation of said pouch.

[0034] According to one possible feature, said mixing arm is movable between: - said mixing position, and - a storage position in which it extends outside of said internal volume delimited by said pocket.

[0035] 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.

[0036] 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 able to move said mixing arm when it is in its mixing position. 5. Description of the figures

[0037] 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:

[0038] [Fig-1] [Fig.1] illustrates a perspective view of a device according to the invention of which the mixing arm is in the storage position;

[0039] [Fig.2] [Fig.2] illustrates a perspective view of a device according to the invention of which the mixing arm is in the mixing position;

[0040] [Fig. 3] [Fig. 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;

[0041] [Fig.4] [Fig.4] illustrates a perspective view of a mixing arm of a device according to the invention with a rectangular cross-section;

[0042] [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.

[0043] 6. Description of particular embodiments 6.1. Device 6.1.1. General Structure

[0044] An example of a processing device according to the invention is presented in relation to figures 1 to 6.

[0045] Such a device comprises a pocket 1. Such a pocket 1 is sometimes referred to in the field of metallurgy by the following names depending on the context in which it is used:

[0046] - transfer pocket;

[0047] - pouring pocket;

[0048] - treatment bag;

[0049] - mixing pouch.

[0050] 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.

[0051] 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.

[0052] 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 pouring spouts 13. The top opening 12 of the bag 1 can be closed by means of a removable lid 2.

[0053] The removable cover 2 itself has an opening 20 leading into the pocket 1.

[0054] 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.

[0055] Molten metal means a metal or an alloy of metals. Molten metal may, for example, be cast iron, a ferrous alloy, a light alloy, a copper alloy, or any other alloy or metal.

[0056] The inner peripheral wall 100 and the inner bottom wall 110 are essentially smooth. In other words, they do not have mixing blades projecting towards the center of the pocket, as is the case with the known solution described previously in the section devoted to the prior art. Of course, these walls However, they may exhibit surface irregularities resulting, for example, from the process used to manufacture the bag.

[0057] The device includes means for rotating the pouch 1 around an axis of rotation. This axis of rotation is substantially coincident with the longitudinal axis A of the pouch 1 and extends preferentially essentially vertically, although it could be inclined.

[0058] The device also includes control means 4 for the rotation drive means 3, which allow, in particular, programming the rotation frequency of the pouch 1, its direction of rotation, the duration of the rotation cycles...

[0059] 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.

[0060] 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.

[0061] This mixing arm 5 is mounted to move between at least two positions, namely:

[0062] - a storage position, illustrated in [Fig. 1], in which it extends outwards of the internal volume 14 delimited by pocket 1, and

[0063] - a mixing position, illustrated in [Fig.2], in which it is at least partially immersed inside the internal volume 14 delimited by the pocket 1, and immobile relative to the pocket.

[0064] 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.

[0065] These drive means may 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 of its positions to another) may be used to perform this function.

[0066] These drive means 6 here include a mast 60, which extends essentially vertically. 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.

[0067] The mixing arm 5 is fixedly connected to the support 63, which extends essentially parallel to the mast 60.

[0068] The drive means 6 comprise a motor 65 connected to the beams 61, by a transmission T configured to transform a rotational movement of the rotor of the motor 65:

[0069] - in a rotational movement of the beams 61 around the axes of the pivot joints 62 compared to the 60-meter mast, and

[0070] - in a rotational movement of the beams 61 around the axes of the pivot joints 64 compared to support 63.

[0071] 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 movements, the mixing arm 5 remains essentially parallel to the mast 60 and to the axis of rotation A of the ladle 1.

[0072] The transmission T, which connects the motor rotor 65 to the beams 61, includes for example a worm gear system. 6.1.2. Mixing arm

[0073] The mixing arm 5 may have a quadrangular cross-section in a plane orthogonal to the axis of rotation A of the pocket 1.

[0074] 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 1. However, in a variant, its section may be square or otherwise.

[0075] The mixing arm 5 then comprises, in addition to its upper faces 55 and lower faces 54, four lateral faces, namely:

[0076] - a first face 50 oriented towards the inner peripheral wall 100 of the pocket1;

[0077] - a second face 51 oriented towards the axis of rotation A of the pocket 1;

[0078] - a third face 52 joining faces 50, 51, essentially orthogonal to these;

[0079] - a fourth face 53 for joining faces 50, 51, essentially orthogonal to these.

[0080] 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.

[0081] The length L will preferably be between 25 and 40% of the inner radius of the pocket, and even more preferably of the order of 1 / 3 of the inner radius of the pocket.

[0082] The length 1 will preferably be between 30 and 50% of the value of L.

[0083] 6.1.3. Arrangement of the mixing arm inside the bag in its position of blend

[0084] The first lateral face 50 of the mixing arm 5, oriented towards the inner peripheral wall 100 of the pouch 1, is separated from it by a distance XB. This distance XB will be determined experimentally to optimize the flow within the rotating pouch. This distance XB will preferably be between 1 and 20% of the inner radius of the pouch.

[0085] The lower face 54 of the mixing arm 5 is separated from the inner bottom wall of the ladle by a distance ZB. 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.

[0086] The pocket 1 has a median or diametrical plane P passing through its axis of rotation A.

[0087] 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.

[0088] The offset will be chosen such that, when the ladle 1 is rotated about its axis A, the molten metal in the ladle 1 strikes the mixing arm 5 with 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.

[0089] This distance YB will be determined experimentally to optimize the flow circulation within the rotating pocket. This distance YB will preferably be between 0 and 20% of the inner radius of the pocket.

[0090] In one variant, the median plane of the mixing arm 5 may pass through the axis of rotation A of the pouch 1. 6.2. Operation 6.2.1. General Operation

[0091] 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.

[0092] Molten metal is introduced into the ladle 1.

[0093] The mixing arm 5 is placed in its mixing position.

[0094] The pouch 1 is driven in rotation about its axis A of rotation. Such a pouch 1 preferably operates at a constant rotational speed without requiring successive accelerations / decelerations / stops and without reversing its direction of rotation.

[0095] The mixing arm, in its mixing position, remains stationary relative to the bag which is moving in a rotational motion.

[0096] However, in practice, the mixing arm is occasionally moved, particularly in a back-and-forth motion, along the radius of the ladle, or more generally in a plane containing the axis of rotation of the ladle or in a plane parallel to a plane containing the axis of rotation of the ladle, 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 liquid bath where grains of processing products and / or alloying elements tend to stagnate, thus hindering the proper mixing of these elements with the molten metal.

[0097] Reagent is injected into the pocket 1 at the surface of the molten metal. 6.2.2. Effect of the mixing arm

[0098] The use of a mixing arm 5 induces a mixing of the reactant particles, which are 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 again to a peripheral region of the ladle. 6.3. Advantages

[0099] 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 many advantages including: - obtaining an optimal mixture of reactant(s) in the molten metal contained in the ladle; - possible processing of a large quantity of metal in the ladle, in particular more than 2 tonnes; - treatment feasible with a single direction of rotation and at a substantially constant speed without requiring reversal of the direction of rotation of the bag and acceleration / deceleration of the bag; - few maintenance campaigns due to the removal of the mixing blades on the internal faces of the bag which tend to get clogged in the solutions of the prior art; - improved productivity; - simple and robust technique; - lower 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 result in some of the liquid alloy being projected out of the ladle by the rise in the level of The liquid alloy is placed on the periphery of the ladle. Mixing is then 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 raising the level of the liquid alloy on the periphery. Avoiding a deep central vortex ensures safe processing and allows the ladle to be used at its full capacity.

Claims

Demands

1. Device for processing molten metal, said device comprising a ladle defining an internal volume intended to contain said molten metal, and means for rotating said ladle about an axis of rotation, characterized in that said ladle 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 internal volume of said ladle and in which it is fixed relative to said ladle.

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

3. Device according to claim 2 in which 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.

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

5. Device according to any one of claims 1 to 4 in which said mixing arm comprises a lower face oriented towards and distant from said inner bottom wall of said pocket.

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

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

8. A device according to any one of claims 1 to 7 in which 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.

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

10. Device according to any one of claims 1 to 9 comprising 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.

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