Continuous casting equipment

Abstract

The invention relates to a continuous casting plant for manufacturing a composite metal blank or block, comprising a nozzle located between a tundish and a crystallizer, said nozzle comprising:-an upper portion arranged downstream of the tundish,-a dome arranged at the inlet of the upper portion, and-a nozzle arranged between the upper portion and the crystallizer, the invention relates to a device for separating a flow of liquid metal, comprising means for separating an initial flow of liquid metal,-an inner wall located below a dome creating at least two mixing chambers,-means for injecting powder through the dome to allow mixing with the liquid metal,-a lower part comprising at least a central channel and a side channel, the side channels are arranged in the central channel so as to allow liquid metal to flow into the crystallizer through at least one outlet of each channel, and the side channels are longer than the central channel. The invention also relates to a method for continuous casting using the continuous casting equipment related to the invention.

Description

Technical Field

[0001] The present invention relates to continuous casting equipment. In particular, the present invention relates to a continuous casting nozzle for manufacturing a composite metal billet or ingot, which has an improved design. Background Art

[0002] Continuous casting of steel is a well-known process. It includes injecting liquid metal from a ladle into a tundish for flow regulation, and then injecting the metal into the upper part of a water-cooled bottomless copper mold that moves vertically back and forth. The solidified semi-finished product is taken out from the lower part of the mold by rollers. The liquid metal is introduced into the mold by means of a tubular conduit called a nozzle arranged between the tundish and the mold.

[0003] However, such a simple device is not suitable for casting composite metal products. The nozzle is a simple conduit that can only be used as a pouring tool for liquid metal between the tundish and the mold. Therefore, the nozzle and the casting method must be modified to allow casting of composite metal products.

[0004] Japanese Patent Application JP11197807 describes a continuous casting nozzle for manufacturing a multi-layer casting, which is formed by a vertical conduit having a plurality of discharge ports in the vertical direction. The conduit is internally separated by partition walls to form a plurality of molten steel flow passages, and has one or more ports for adding raw materials.

[0005] The described continuous casting nozzle allows two types of molten metal with different compositions to be injected into the mold at different heights, thereby forming two liquid metal pools, namely an upper pool and a lower pool, each with a different composition. The metal in the upper pool solidifies first, forming a shell with the composition of the upper pool. The metal in the lower pool then solidifies inside the shell, forming the main body of the material piece and having the composition of the lower pool, thereby producing a composite metal product.

[0006] When manufacturing a composite metal product by continuous casting, in order to obtain a product with excellent quality, it is necessary to achieve very good stability of the two liquid metal pools entering the mold and the liquid metal flow from the nozzle, and very good uniformity of the pool compositions.

[0007] Japanese Patent Application JP11197807 uses a static magnetic field, and injects different liquid metal flows above and below the magnetic field to stabilize the two pools.

[0008] However, the solutions proposed in the prior art do not provide sufficient solutions in terms of the stability of different liquid metal flows and the uniformity of liquid metal pools. In addition, the specific magnetic field brings complexity to the casting operation. Summary of the Invention

[0009] The present invention discloses a continuous casting nozzle for manufacturing composite metal products, which has an improved design, thereby allowing better stability of the liquid metal flow and better uniformity of the liquid metal bath in the case of simple equipment.

[0010] A first object of the present invention is a continuous casting apparatus for manufacturing a composite metal billet or ingot, the continuous casting apparatus comprising a nozzle 1, a tundish 2 and a mold 3, the nozzle 1 being located between the tundish 2 and the mold 3, the nozzle 1 comprising:

[0011] - an upper part 4, which is arranged downstream of the tundish 2 with respect to the advancing direction of the liquid metal,

[0012] - a dome 6, which is arranged at the inlet of the upper part 4, the dome 6 comprising means for dividing an initial liquid metal flow into at least two separate flows,

[0013] - an inner wall 8, which is located below the dome 6, generating at least two mixing chambers 9a, 9b, the separate flows of the liquid metal flowing in each of the chambers 9a, 9b respectively,

[0014] - means 10 for injecting powder through the dome 6 into at least one of the chambers 9a, 9b to allow mixing with the liquid metal flowing into the chambers 9a, 9b,

[0015] - a lower part 5, which at least comprises a central channel 12a and side channels 12b, 12c, the central channel 12a and the side channels 12b, 12c extending from the upper part 4 into the mold 3, the central channel 12a being connected to one of the chambers 9a, 9b, the central channel 12a being longer than the side channels 12b, 12c, and the side channels 12b, 12c being connected to at least another chamber 9b, wherein the central channel 12a allows the liquid metal to flow into the mold 3 through at least one bottom outlet 14 which opens the bottom of the channel 12a, and the side channels 12b, 12c allow the liquid metal to flow into the mold 3 through at least two side outlets 13 of each channel.

[0016] The continuous casting apparatus according to the present invention may also have optional features which are considered individually or in combination as listed below:

[0017] - The side channels 12b, 12c have a triangular cross-section with rounded corners,

[0018] - The side outlets 13 are located on the same horizontal plane and on two of the faces of the triangular cross-section of the side channels 12b, 12c,

[0019] - The axes of the side outlets 13 are positioned towards the middle zone of the face of the mold.

[0020] - The axis of the side outlet 13 has an angle β with respect to the horizontal plane,

[0021] - The dome 6 further includes means 11 for injecting gas through the dome 6,

[0022] - The dome 6 further includes a support arm 7.

[0023] The second object of the present invention is a method for continuously casting a composite metal blank or billet using the continuous casting equipment according to the present invention, wherein:

[0024] - Injecting liquid metal into the tundish 2 located above the continuous casting nozzle 1,

[0025] - The liquid metal flows from the tundish 2 into the upper part 4 of the casting nozzle 1, thereby forming an initial flow,

[0026] - The initial flow impinges on the dome 6, thereby dividing it into a defined number of separate flows,

[0027] - The separate flows flow into the mixing chambers 9a, 9b of the nozzle 1,

[0028] - Injecting powder into one of the chambers 9a, 9b and mixing it with the liquid metal flow flowing into the chambers 9a, 9b, thereby changing the composition of the liquid metal flow,

[0029] - Then distributing the separate flows into the channels 12a, 12b, 12c of the lower part of the continuous casting nozzle 1,

[0030] - Injecting the liquid metal into the mold 3, wherein the liquid metal flowing in the side channels 12b, 12c is injected into the mold through the side outlets 13, and the liquid metal flowing into the central channel 12a is injected deeper into the mold through the bottom outlet 14, thereby forming two different liquid metal pools 15, 16 in the mold 3.

[0031] The continuous casting method according to the present invention may also have optional features that are considered separately or in combination as listed below:

[0032] - The liquid metal is steel,

[0033] - The powder is injected into the chamber 9a connected to the central channel,

[0034] - The liquid metal in the upper pool 15 in the mold 3 consists only of the base metal from the tundish 2, and the liquid metal in the lower pool 16 in the mold 3 consists of the base metal from the tundish 2 mixed with the powder injected below the dome 6,

[0035] - The powder is injected into chamber 9b which is connected to the side channel.

[0036] - The liquid metal in the upper molten pool 15 in the crystallizer 3 is formed by mixing the base metal from the tundish 2 with the powder injected below the dome 6, and the liquid metal in the lower molten pool 16 in the crystallizer 3 consists only of the base metal from the tundish 2. Description of the Drawings

[0037] The present invention will be described in a non - limiting manner with reference to the following drawings:

[0038] - Figure 1 : General view of the nozzle in the use configuration according to the present invention.

[0039] - Figure 2 : View of the bottom of the lower part of the nozzle.

[0040] - Figure 3 : Dome as viewed from above for the bulk alloying embodiment.

[0041] - Figure 4 : Dome as viewed from above for the shell alloying embodiment.

[0042] - Figure 5 : A - A cross - sectional view of the nozzle's upper part below the dome in Figure 1

[0043] - Figure 6 : B - B cross - sectional view of the lower part of the nozzle entering the crystallizer, with a representation of the convection, - Figure 7 : Immersion part of the nozzle, with a representation of the flow in the crystallizer.

[0044] - Figure 8 : Cross - section of the composite metal billet obtained by continuous casting.

[0045] - Figure 9 : Figure 1 Cross - sectional view of the mixing chamber of the nozzle in Detailed Description of the Invention

[0046] The object of the present invention is to cast a composite metal billet or ingot. The billet and the ingot are long products with a square cross - section, as Figure 8 shown. The area of the billet is less than 230 cm 2 , and the area of the ingot is greater than 230 cm 2 .

[0047] Figure 1 Fig. shows the nozzle 1 provided between the tundish 2 and the crystallizer 3. The nozzle includes an upper part 4 and a lower part 5.

[0048] The dome 6 is provided at the entrance of the upper part 4 and closes a part thereof. The top of the dome 6 preferably has an inclined surface at a certain angle, for example greater than 15°. The dome 6 also has lateral sides which preferably form a sharp edge with the inclined surface. The dome 6 is fixed to the upper part 4 by one or more support arms 7.

[0049] The inner wall 8 located below the dome 6 creates at least two mixing chambers 9a, 9b in the upper part 4. In Figure 1 the configuration shown, there are two chambers 9a, 9b.

[0050] The upper part 4 further includes a device 10 for injecting powder and a device 11 for injecting gas. The device 10 and the device 11 are each partly located in one of the support arms 7 and pass through the dome 6. The device 10 for injecting powder can be, for example, an endless screw connected to a powder tank.

[0051] Figure 3 The configuration of the dome 6 is shown, which has three support arms 7 and has a passage 10 for powder injection located in one of the support arms 7 and two passages 11 for gas injection located in the other two support arms 7.

[0052] Figure 4 Another configuration of the dome 6 is shown, which also has three support arms 7, but different from the Figure 3 configuration shown, it has two passages 10 for powder injection located in two of the support arms 7 and one passage 11 for gas injection located in the other support arm 7. In this configuration, the two passages 10 for powder injection can be connected to two different powder injectors, and the powder injectors each have different types of powder.

[0053] The dome 6 can also include other configurations with fewer or more support arms. For example, a configuration with four support arms 7 can be considered.

[0054] As Figure 1 shown, the lower part 5 of the nozzle 1 includes three channels 12a, 12b, 12c which extend from the mixing chambers 9a, 9b of the upper part 4 and terminate at the crystallizer 3. The side channels 12b, 12c lead to the crystallizer 3 by means of two side outlets 13 of each channel. The central channel 12a leads to the crystallizer by means of a bottom outlet 14. Figure 2 A magnified view of one side of the bottom of the lower part 5 of the nozzle 1 for the Figure 1 configuration shown is shown. The axis of the side outlet 14 forms an angle β with respect to the horizontal plane. The angle β is preferably from 10° to 30°. This angle is directed downwards.

[0055] In the present embodiment, the channels 12a, 12b, 12c have a circular shape. In a preferred embodiment, the central channel 12a has a circular or elliptical cross-section. In a preferred embodiment, the side channels 12b, 12c have a triangular cross-section with rounded corners, and their side outlets 13 are on the same horizontal plane and on two faces of the triangular cross-section. This configuration positions the axes of the side outlets 13 towards the middle region of the mold face. Figure 6 The preferred configuration is shown in.

[0056] Figure 5 Shown in Figure 1 is a sectional view A-A of the nozzle 1 in the configuration depicted in. Figure 3 and Figure 4 are arranged in the same orientation as Figure 5 the same. Figure 3 can be overlapped with Figure 5 to obtain a sectional view of the nozzle 1 above the dome 6. This can also be applied to Figure 4 and Figure 5 to obtain a view of another configuration.

[0057] As Figure 5 shown in, the inner wall 8 has a V-shape, thus forming two mixing chambers 9a, 9b with different volumes. The chamber 9a located inside the V-shape is connected to the central channel 12a, and the chamber 9b located outside the V-shape is connected to the side channels 12b, 12c.

[0058] In other configurations, the inner wall 8 has a different shape and forms a different number of chambers. For example, a Y-shape can form three chambers with different volumes, or a simple wall can form two chambers with exactly the same volume.

[0059] As Figure 1 shown in, the central channel 12a is longer than the two side channels 12b, 12c, and thus leads deeper into the mold 3. In this embodiment, the three channels are aligned, as Figure 5 shown in.

[0060] Other configurations can be considered. For example, a third side channel that is not aligned with the other channels 12a, 12b, 12c can be added to form another geometry.

[0061] In a preferred embodiment, the ratio between the diameter of the side outlet 13 and the distance between the side outlet 13 and the mold 3 is greater than 0.5 and less than 1.

[0062] In a preferred embodiment, the ratio between the diameter of the side outlet 13 and the diameter of the side channels 12b, 12c is greater than 0.8 and less than 1.

[0063] The present invention has two preferred embodiments for its uses respectively called bulk alloying and shell alloying. Only the differences between the two preferred embodiments will be described separately. Figure 1 The present invention in a use configuration is shown.

[0064] Liquid metal of a determined composition is poured from a ladle into a tundish 2. In a preferred embodiment, the liquid metal is steel, and the use of the nozzle 1 will be described together with it. The steel flows into the upper part 4 of the continuous casting nozzle 1, thus forming an initial flow. The stopper rod 19 allows controlling the initial flow rate.

[0065] The dome 6 placed on a track made of steel forces the initial flow to impinge on the dome 6. The slope of the dome 6 makes the steel flow towards its edge. The support arms 7 form different regions on the dome 6, thus dividing the steel into a plurality of separate flows. The number of the separate flows is determined by the design of the dome 6 and its support arms 7. In this particular embodiment, the number of the separate flows is three.

[0066] The separate flows then flow into different mixing chambers 9a, 9b. Figure 9 A sectional view of the mixing chamber is shown. In this configuration, a part of the flow flows into the chamber 9a inside the V - shape, and another part flows into the chamber 9b outside the V - shape. Powder is injected into one of the mixing chambers 9a, 9b simultaneously. The design of the chamber having a large cross - section at the top allows the steel to flow down from the dome like a waterfall, and allows the powder to be injected into the flow without the steel contacting the device for injecting the powder. The reduction of the cross - section of the chamber allows the steel to slow down and accumulate in the chambers 9a, 9b. The reduction of the cross - section of the chamber allows the steel to be agitated inside the chamber. Thus, the powder can be effectively mixed with the steel entering the chambers 9a, 9b to change its composition, and the powder starts to melt. This step allows the liquid steel into which the powder is injected to become homogeneous. The reduction of the cross - section of the chamber can be achieved by walls of various configurations. For example, the reduction can be done with regular slopes or steps or any method for reducing the cross - section.

[0067] The powder injected into the steel can have various compositions. For example, it can be FeSi, Ni, FeAl, FeTi, FeCr, FeNb, FeB, FeCe, FeMo, etc.

[0068] The powder addition step is different between the two preferred embodiments. For the bulk alloying embodiment, the powder is injected into the chamber 9a inside the V - shape by means of at least one powder injection device 10, Figure 3 Only one injection device is shown, while for the shell alloying embodiment, the powder is injected into the chamber 9b outside the V - shape by means of at least one powder injection device 10, Figure 4 Two powder injection devices are shown.

[0069] In two embodiments, the injection of the powder is facilitated by a gas injection device 11 that generates a gas flow that maintains the flow of steel downward along the dome 6 towards the exterior of the upper portion 4, thereby creating a steel-free zone below the dome 6. This hollow zone prevents any contact between the steel and the powder injection device 10, thus avoiding potential clogging of the powder injection device 10.

[0070] The gas is preferably a non-oxidizing gas, such as Ar, to prevent any reaction with the steel during casting.

[0071] After injection, the two mixing chambers 9a, 9b contain two types of steel with different compositions.

[0072] Then, the steel flows into the channels 12a, 12b, 12c in the lower portion 5 of the nozzle 1, which are connected to the chambers after the cross-section of the chambers is reduced, as Figure 1 or Figure 9 shown. The steel in the chamber 9a located inside the V-shape flows into the central channel 12a, and the steel in the chamber 9b located outside the V-shape flows into the side channels 12b, 12c. Then, the different steels are injected into the mold 3 through the outlets 13, 14 of the channels 12a, 12b, 12c.

[0073] Since the central channel 12a is longer than the side channels 12b, 12c, the steel from the central channel 12a is injected deeper into the mold 3. This configuration allows the two types of steel to be injected into the mold 3 at different heights, thereby creating two steel pools, namely the upper pool 15 and the lower pool 16 with different compositions. The upper pool 15 is formed by the steel from the side channels 12b, 12c, and the lower pool 16 is formed by the steel from the central channel 12a.

[0074] During use, the outlets 13, 14 of the nozzle 1 are immersed in different steel pools. The side outlets 13 of the side channels 12b, 12c are immersed in the upper pool 15, and the bottom outlet 14 of the central channel 12a is immersed in the lower pool 16.

[0075] According to the embodiment, the compositions of the pools are different.

[0076] For the bulk alloying embodiment, the composition of the upper pool 15 is only the composition of the steel from the tundish 2. The composition of the lower pool 16 is a combination of the composition of the steel from the tundish 2 and the composition of the injected powder.

[0077] For the shell alloying embodiment, the composition of the upper pool 15 is a combination of the composition of the steel from the tundish 2 and the composition of the injected powder. The composition of the lower pool 16 is only the composition of the steel from the tundish 2.

[0078] In two embodiments, in the mold 3, the steel in the upper molten pool 15 solidifies first, thereby forming the outer shell 17. The steel in the lower molten pool 16 then solidifies inside the outer shell 17, thereby forming the main body 18 of the material piece. After complete solidification, the obtained material piece is a composite metal billet or ingot, which has different compositions in its outer shell and its main body.

[0079] In order to cast a composite metal billet or ingot with sufficient quality, each molten pool must have a uniform composition, and the boundary between them must be stable. These factors are affected by the characteristics of the different liquid metal flows from the nozzle 1.

[0080] The design of the nozzle 1 - which has at least four side outlets 13, and the axes of the at least four side outlets 13 are positioned towards the middle region of each mold face - allows the flow in the mold to be symmetric in all directions, as Figure 6 shown, thus ensuring the uniformity of the two molten pools 15, 16, because the mold has a square cross-section.

[0081] These flows generated by the design of the nozzle ensure the stability of the boundary between the two liquid metal molten pools 15, 16.

[0082] For example, in the configuration shown in Figure 7 , the flow from the side outlet 13 forms a main upward flow 20 and a secondary downward flow 21 with a smaller flow rate in the upper molten pool 15 when it meets the face of the mold 3. At the same time, the flow from the bottom outlet 15 generates a flow 22 in the shape of a vortex in the lower molten pool 16.

[0083] The design of the outlets affects the stability and uniformity of the boundary between the two molten pools because the outlets affect the initial direction and velocity of the flow. Those skilled in the art will determine the characteristics of the outlets 13, 14 to optimize these parameters. Among these characteristics, the ratio of the diameter of the outlet to the diameter of the channel, the ratio of the diameter of the outlet to the distance between the outlet and the mold 3, and the angle β of the axis of the outlet relative to the horizontal plane can be considered.

[0084] In a preferred embodiment, the angle β of the axis of the side outlet 13 relative to the horizontal plane is between 10° and 30°, because this allows the stability of the two molten pools to be optimized.

[0085] In a preferred embodiment, the ratio of the diameter of the side outlet 13 to the distance between the outlet 13 and the mold is greater than 0.5 and less than 1.

[0086] In a preferred embodiment, the ratio of the diameter of the side outlet 13 to the diameter of the side channels 12b, 12c is greater than 0.8 and less than 1.2.

[0087] In a preferred embodiment, the nozzle 1 mainly consists of refractory material surrounded by a metal ring.

[0088] The continuous casting nozzle 1 meets the expectations in terms of stability and uniformity in its use configuration. It allows a stable casting speed, and the different liquid metal flows allow a high degree of stability and a high degree of uniformity in the heights of the two molten pools entering the mold 3. This stability results in high-quality semi-finished products that have a well-defined compositional gradient between their outer shell and their body.

Claims

1. A continuous casting device for manufacturing a composite metal billet or blank, the continuous casting device comprising a nozzle (1), a tundish (2) and a mold (3), the nozzle (1) being located between the tundish (2) and the mold (3), the nozzle (1) comprising: - an upper part (4), the upper part (4) being arranged downstream of the tundish (2) with respect to the direction of travel of the liquid metal, - a dome (6), the dome (6) being arranged at the inlet of the upper part (4), the dome (6) comprising means for dividing an initial liquid metal stream into at least two separate streams, - an inner wall (8), the inner wall (8) being located below the dome (6), thereby creating at least two mixing chambers (9a, 9b), the separate streams of liquid metal flowing in each of the chambers (9a, 9b), - means (10) for injecting powder through the dome (6) into at least one of the chambers (9a, 9b) to allow mixing with the liquid metal flowing into the chambers (9a, 9b), - a lower part (5), the lower part (5) comprising at least a central channel (12a) and side channels (12b, 12c), the central channel (12a) and the side channels (12b, 12c) extending from the upper part (4) into the mold (3), the central channel (12a) being connected to one of the chambers (9a, 9b), the central channel (12a) being longer than the side channels (12b, 12c), and the side channels (12b, 12c) being connected to at least another chamber (9b), wherein the central channel (12a) allows the liquid metal to flow into the mold (3) through at least one bottom outlet (14) that opens the bottom of the channel (12a), and the side channels (12b, 12c) allow the liquid metal to flow into the mold (3) through at least two side outlets (13) of each channel.

2. The continuous casting device according to claim 1, wherein, The side channels (12b, 12c) have a triangular cross-section with rounded corners.

3. The continuous casting device according to claim 2, wherein, The side outlets (13) are located on the same horizontal plane and on two of the faces of the triangular cross-section of the side channels (12b, 12c).

4. The continuous casting device according to claims 1 to 3, wherein, The axes of the side outlets (13) are positioned towards the middle zone of the face of the mold (3).

5. The continuous casting device according to any one of the preceding claims, wherein, The axes of the side outlets (13) have an angle β with respect to the horizontal plane.

6. The continuous casting device according to any one of the preceding claims, wherein, The dome (6) further comprises means (11) for injecting gas through the dome (6).

7. The continuous casting device according to any one of the preceding claims, wherein, The dome (6) further comprises support arms (7).

8. A method for continuously casting a composite metal billet or blank using the continuous casting device according to any one of the preceding claims, wherein: - injecting liquid metal into a tundish (2) located above the continuous casting nozzle (1), - the liquid metal flowing from the tundish (2) into the upper part (4) of the casting nozzle (1), thereby forming an initial stream, - the initial stream impinging on the dome (6), thereby dividing the initial stream into a defined number of separate streams, - the separate streams flowing into the chambers (9a, 9b) of the nozzle (1), - injecting powder into one of the chambers (9a, 9b) and mixing the powder with the liquid metal stream flowing into the chambers (9a, 9b), thereby changing the composition of the liquid metal stream, - Then distribute the separated flow into the channels (12a, 12b, 12c) of the lower part of the continuous casting nozzle (1). - Inject the liquid metal into the mold (3), wherein the liquid metal flowing in the side channels (12b, 12c) is injected into the mold through the side outlets (13), and the liquid metal flowing into the central channel (12a) is injected deeper into the mold through the bottom outlet (14), thereby forming two different liquid metal pools (15, 16) in the mold (3).

9. The method according to claim 8, wherein, The liquid metal is steel.

10. The method according to claim 8 or 9, wherein, The powder is injected into the chamber (9a) connected to the central channel.

11. The method according to claim 10, wherein, The liquid metal in the upper pool (15) in the mold (3) consists only of the base metal from the tundish (2), and the liquid metal in the lower pool (16) in the mold (3) is composed of the base metal from the tundish (2) mixed with the powder injected below the dome (6).

12. The method according to claim 8 or 9, wherein, The powder is injected into the chamber (9b) connected to the side channel.

13. The method according to claim 12, wherein,The liquid metal in the upper pool (15) in the mold (3) is composed of the base metal from the tundish (2) mixed with the powder injected below the dome (6), and the liquid metal in the lower pool (16) in the mold (3) consists only of the base metal from the tundish (2).

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