RU2574149C1 - Continuous casting facility - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: claimed facility arranged between teeming device (1) and casting mould (9) comprises the vertical channel including the refractory ring (5), copper tube (3) and immersible pot (8). Dome (2) is arranged inside said refractory ring and includes the inclined top part (16), its inclination angle making 15-25 degrees. Liquid metal getting on the dome top part deflects toward the vertical channel inner walls to produce a circular jet. Copper tube ID (mm) makes Q/3.75-Q/1.25, where Q is the liquid metal rated fluid flow rate equal to 200-800 kg/min to allow a uniform formation of homogeneous this ply of liquid metal long the copper tube.

EFFECT: higher stability of casting.

9 cl, 5 dwg

Description

FIELD OF THE INVENTION

The invention relates to equipment for continuous casting. In particular, the invention relates to continuous casting equipment called the Hollow Jet Nozzle (ring jet nozzle), a new and improved design.

State of the art

Continuous steel casting is a well-known process. It consists in pouring liquid metal from a casting ladle into a casting device designed to regulate the flow, and then, after this casting device, the metal is poured into the upper part of a copper casting mold, which is open from below, and is subjected to vertical reciprocating motion, open from below. The hardened semi-finished product is removed from the bottom of the mold by means of rollers. Liquid steel is introduced into the mold by means of a tubular channel called an annular jet nozzle located between the casting device and the mold.

EP 0 261 180 B1 describes special equipment for continuous casting, called the “Ring Jet Nozzle" (see FIG. 1), in which molten metal is poured onto the upper part of a dome 2 made of refractory material. The shape of this dome 2 leads to the fact that the metal flows to its periphery, while the flow deviates to the inner wall of the nozzle or to the intermediate vertical tubular element. Said intermediate vertical tubular member may be a copper pipe 3 cooled by a water jacket 4, as shown in FIG. 1 topped with a refractory ring 5.

Thus, in the central part of the nozzle, under the intermediate casting element, a volume is created that does not contain liquid metal, in which additives can be introduced through the inlet channel. One or more brackets are located on the upper part of the dome 2 to attach it to the said refractory ring 5. The water-cooled copper pipe 3 forms a heat exchanger that removes heat from the molten steel. Consequently, the overheating of liquid steel is substantially reduced to a liquidus temperature or even below it.

In the center of the hollow stream created by the refractory dome 2, powder can be introduced. This introduction technology is described in EP 0 605 379 B1. This introduction of the powder helps to further cool the liquid steel by melting the metal powder or modifying the composition of the steel during casting by adding other metal elements such as ferroalloys. As described in document EP 2099576 B1, the powder can be transported using a mechanical screw feeder, and it can be supplied by gravity through one of the brackets of the refractory dome and through the refractory dome itself.

It should be understood that in the present application, the expression “HJN equipment” describes the elements shown in FIG. 1, with the exception of the container 10 with powder and powder feeder 11.

During casting using HJN, as described previously, the equipment must often be stopped due to the uneven flow of liquid steel from the casting device 1 into the mold 9 and / or due to the uneven supply of powder, which leads to instability of the casting process, which may clog the HJN or clog the outlet of the powder feed channel.

Disclosure of invention

The purpose of the present invention is to provide equipment for continuous casting, allowing a uniform and stable casting process.

The present invention describes equipment for continuously casting a stream of liquid metal from a casting device into a mold, said equipment comprising:

- a vertical channel located up to the mold relative to the direction of movement of the liquid metal; moreover, the said channel contains (in the order corresponding to the direction of flow) a refractory ring, a copper pipe with an inner diameter D and a submersible casting glass,

- a dome located inside the refractory ring and containing an inclined upper part, said inclined upper part being made so as to deflect liquid metal coming from the casting device to the inner walls of the vertical channel;

characterized in that the diameter D of the copper pipe takes a value from a minimum diameter equal to Q / 3.75 to a maximum diameter equal to Q / 1.25, where Q is the nominal liquid metal flow rate of the equipment, taking values from 200 to 800 kg / min, a D is the diameter, expressed in mm.

In other embodiments, taken separately or in combination, the equipment may also contain the following features:

- the slope α of the upper part of the said dome takes values from 30 to 10º;

- wherein said dome further comprises a side extending from the upper part of the dome to the lower part of the dome, wherein said side at the intersection with the upper part forms a sharp edge with a radius of curvature of less than 2 mm;

- the gap e between said sharp edge and the refractory ring takes values from 10 to 25 mm;

- the distance h between the bottom of the dome and the top of the copper pipe takes values from 10 to 50 mm;

- moreover, the said upper part of the dome further comprises at least one bracket with a fastener for fixing the said dome on the refractory ring, said fastener having a width C taking on values from 10 to 60 mm;

- wherein said at least one bracket comprises an additional part extending from the fastener along the side of the dome, said part being designed so that it directs the flow of molten metal around the bracket and under said bracket;

- wherein said additional portion has converging side walls;

- and the dome is made of high alumina material.

The present invention also describes a process for continuous casting of molten metal with a nominal flow rate Q of 200 to 800 kg / min, using equipment as described above, including a copper pipe with an inner diameter D, the value of which lies in the range from the minimum diameter equal to Q / 3.75 to a maximum diameter equal to Q / 1.25.

The inventors have found that disturbances in the casting process are associated with an inappropriate nozzle design for an annular jet.

Other features and advantages of the invention will become apparent upon reading the following detailed description, given by way of non-limiting example only, with reference to the accompanying drawings.

In FIG. 1 is a sectional view of continuous casting equipment in accordance with the prior art.

In FIG. 2 is a sectional view of continuous casting equipment according to an embodiment of the invention.

In FIG. 3 is a plan view of a dome in accordance with an embodiment of the invention. A sectional view of the dome along the axis AA-AA is also presented.

In FIG. 4 is a plan view of a dome in accordance with another embodiment of the invention. A sectional view of the dome along the axis AA-AA is also presented.

In FIG. 5 is a sectional view and a side view of a dome in accordance with another embodiment of the invention.

The implementation of the invention

As explained previously and as can be seen in FIG. 2, the principle of the ring jet casting process is, in particular, based on the fact that a water-cooled copper pipe 3 removes heat from molten steel. This heat removal creates a layer of hardened steel on a copper pipe; this layer is called overlay 18. Then, molten steel flows into the nozzle along this hardened overlay 18 (the stream of molten steel is shown in dashed lines). This hardened overlay is an integral part of the process, but it should not be too large compared to the diameter D of the copper pipe 3 due to the risk of clogging of the nozzle, which disrupts the flow of liquid steel.

The inventors have found that in order to maximize the heat removed by the copper pipe and reduce the risk of clogging of the nozzle, the diameter D mentioned must be selected depending on the nominal flow rate of the steel of the continuous casting equipment. The proper ratio between the nominal steel flow rate and the diameter D ensures the stable formation of a homogeneous and thin layer of molten steel along the copper pipe. In accordance with the invention, the diameter D should be selected from a minimum diameter equal to Q / 3.75 to a maximum diameter equal to Q / 1.25 (Q / 3.75≤D≤Q / 1.25), where Q is the nominal the steel flow rate in kg / min, taking on a value of 200 to 800 kg / min, and D is the diameter, expressed in mm. For example, for a nominal steel flow rate of 400 kg / min, a diameter D of 195 mm can be selected. As a result, the average heat flux discharged by the heat exchanger is 0.9 MW / m ² for overheating of steel in a casting device equal to 30 ° C.

A major improvement is already noticeable if the diameter D corresponds to the aforementioned range, but, in addition, one or more criteria can be fulfilled to further improve the continuity of the fluid flow and powder supply in the continuous casting equipment in accordance with the invention.

As shown in FIG. 3, the dome 2 includes an upper part 16 with an inclination α, which receives and deflects the molten steel to the wall of the copper pipe to obtain an annular jet, a lower part 17 that allows the powder to be supplied as close to the center of the annular jet as possible, and one or more brackets 7 designed to attach the dome 2 to the refractory ring.

The inclination α of the refractory dome 2 is designed to guarantee a good and stable fall of the liquid steel stream onto the vertical refractory ring 5 and to reduce the perturbations of the molten steel when passing through the dome 2. According to the invention, the inclination varies from 30 to 10 °, preferably from 25 up to 15º, more preferably, the slope is 20º.

In addition, the edge 13, as shown in FIG. 3, formed by connecting the upper part 16 and the side 15 of the lower part 17 of the dome 2, is preferably sharp in order to ensure a straight and even flow of steel when molten metal flows from the upper part of the dome, and thereby ensure that the steel falls properly onto the refractory ring . Preferably, the radius of curvature of the edge 13 is not more than 2 mm, and more preferably, it does not exceed 1 mm. The dome material must be strong enough so that this edge remains sharp throughout the entire process of continuous casting. Preferably, the dome 2 was made of high alumina material.

The gap e, as shown in FIG. 3, between the dome 2 and the vertical refractory ring 5, also affects the fluid flow. The gap Ε should be large enough to prevent the formation of steel plugs between the dome 2 and the vertical refractory ring 5, but not too large. If this gap is too large, the molten steel cannot reach the refractory ring 5. According to the invention, the gap e between the edge 13 of the dome 2 and the vertical refractory ring 5 varies from 10 to 25 mm, preferably from 13 to 20 mm, more preferably The gap is 15 mm.

Also, as shown in FIG. 2, it is preferable to provide a minimum distance h between the bottom of the refractory dome 2 and the top of the copper pipe 3, in order to avoid problems associated with clogging at the outlet of the gap between the dome 2 and the refractory ring 5, and to avoid problems associated with undesirable solidification of the molten steel under the dome 2 , which may interfere with the proper flow of powder in the center of the nozzle. This distance h varies from 10 to 50 mm, preferably from 15 to 35 mm, and more preferably is 30 mm.

The dome bracket (s) can also interfere with the flow of fluid under the dome, which can lead to undesired solidification of the molten steel under the dome. This uncontrolled solidification can affect the feed powder and disrupt the flow of powder into the ring stream. The number, size and shape of the brackets mentioned should be selected so as to avoid these problems.

The number of brackets may vary from one, as shown in FIG. 4, up to six (not shown), to always guarantee the proper flow of molten steel from the casting device into the copper pipe. A preferred configuration is with three brackets. In this configuration, the fluid flow is symmetrically deflected by the dome, and the load on the brackets is evenly distributed.

As shown in sectional view in FIG. 3, the bracket 7 is located on the upper part 16 of the dome 2. It extends from the center of this upper part to the area outside the dome 2. The bracket 7 contains a fastener 14 located outside the dome 2 and designed to attach the bracket 7 to the refractory ring vertical channel.

This fastener 14 has a width C, which should be made as small as possible to maximize the cross-sectional area of the steel flow along the perimeter of the copper pipe, while maintaining a sufficient support function. Width C can vary from 10 to 60 mm, depending on the number of brackets. For example, in a configuration with three brackets, as in FIG. 3, the width C of the bracket is 40 mm. These brackets are separated by an arc of length S, the same between any two brackets, to ensure a symmetrical flow of molten steel. Then, the cross-flow area of steel is three times the length S of the arc separating the two brackets.

In FIG. 3 and 4, the bracket 7 extends only along the upper part 16 of the dome 2. In this configuration, the steel flow is disrupted by the bracket 7, and an area without liquid steel forms under the bracket 7. In order to direct the flow of molten steel around and under the bracket 7, as shown in FIG. 5, the bracket 7 may include an additional part 12 extending from the fastener 14 along the side 15 of the dome 2. The shape of this additional part 12 is designed so that the molten metal flowing around the bracket converges under the bracket. Preferably, the additional part 12 has converging side walls. This design increases the homogeneity of the liquid steel stream along the perimeter of the copper pipe and maximizes the amount of heat removed by the heat exchanger.

The present invention has been illustrated for the continuous casting of steel, but can be extended to the casting of other metals or metal alloys, such as copper.

Claims (9)

1. Equipment for the continuous casting of liquid metal from a casting device (1) into a mold (9) containing:
- a vertical channel located above the mold (9) relative to the direction of movement of the molten metal, formed by a refractory ring (5) located in the direction of flow of the molten metal, a copper pipe (3) and a submersible casting nozzle (8),
- a dome (2) located inside the refractory ring (5) and containing an inclined upper part (16), configured to deflect liquid metal coming from the casting device (1) to the inner walls of the vertical channel,
- moreover, the inner diameter D (mm) of the copper pipe (3) is from a minimum value equal to Q / 3.75 to a maximum value equal to Q / 1.25, where Q is the nominal flow rate of liquid metal, from 200 to 800 kg / min, characterized in that the angle of inclination α of the upper part of the said dome (2) is from 25 to 15 °. 2. Equipment according to claim 1, wherein said dome (2) comprises a side (15) extending from the upper part (16) of the dome to the lower part (17) of the dome, said side (15) at the intersection with the upper part (16) forms a sharp edge (13) with a radius of curvature of less than 2 mm 3. Equipment according to claim 2, in which the gap e formed between said sharp edge (13) and the refractory ring (5) is from 10 to 25 mm. 4. Equipment according to claim 2 or 3, in which the distance h between the bottom (17) of the dome and the top of the copper pipe (3) is from 10 to 50 mm. 5. Equipment according to any one of paragraphs. 1-3, in which said upper part (16) of the dome comprises at least one bracket (7) with a fastener (14) for fixing said dome (2) on the refractory ring (5), said fastener (14) having width C, taking values from 10 to 60 mm. 6. Equipment according to claim 5, wherein said at least one bracket (7) comprises a part (12) extending from the fastener (14) along the side (15) of the dome, said part (12) being made with the possibility of direction molten metal flow around the bracket (7) and under said bracket (7). 7. Equipment according to claim 6, wherein said part (12) has converging side walls. 8. Equipment according to claim 1, in which the dome (2) is made of high alumina material. 9. The method of continuous casting of liquid metal using equipment according to one of paragraphs. 1-3 or 8, containing a copper pipe (3) with an inner diameter D of from a minimum value equal to Q / 3.75 to a maximum value equal to Q / 1.25, where Q is the nominal flow rate of liquid metal, in which casting is carried out with a nominal flow rate Q, taking values from 200 to 800 kg / min.

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