KR20000005253A - Continuous casting ingot mold for metal vertical casting - Google Patents

Abstract

PURPOSE: An ingot mold for continuous molding is provided to effectively cool the quantum on the upper part of the tube of a mold contacted close by passing the upper edge contacted with a refractory feed head and the bottom surface to prevent the deformation of the point contacted with the molten metal. CONSTITUTION: The ingot mold has:a tubular metal member(4) made up of copper or copper alloy to solidify the surrounding of a molding metal according to the contacting with the inner wall of the metal member after circulating water around the outer wall of the metal member and cooling; and a heat insulating refractory material supply bush(9) not cooled to finite a continuous scale measurement channel for molding metal and to be extended toward the upper part of the cooled metal member to contain liquid molding metal.

Description

Continuous casting ingot molds for vertical casting of metal

The present invention relates to continuous casting of metals, in particular steel. This particularly relates to the technique of "vertical hot melt continuous casting".

The first article of this technology has already been published at the end of the sixties, a good example is FR-A-2,000,365. It is then carried by a tundish positioned above the feed head in a liquid state on top of the actively active component of the mold, ie the actively cooled tubular metal component in which the desired solidification of the cast metal is initiated and done. The fact that there is a thermally insulating feed head intended to contain molten metal is distinguished from conventional vertical continuous casting which is now very widely implemented worldwide.

This "active" component is conventionally a tube made of a single piece (for casting valets or blooms) or made of a plate (for casting slabs or large blooms) joined together. It is made of copper, or a copper alloy, and is also actively cooled by intense circulation of water with respect to the outer wall of the component in order to make it possible to induce sufficient heat flux so that the molten metal solidifies in contact with the inner wall of the component. To ensure.

These two successive components allow the cast metal to enter the molten state via the top and pass through the bottom in the form of a solid shell resulting from the peripheral solidification of the cast metal in contact with the cooling wall of the casting body and a stationary liquid core ( Define a continuous sizing passage that includes a still-liquid core. The solidification then continues by terminating solidification at the bottom of the casting machine by the injection device.

The basic advantage found in vertical hot melt continuous casting is the inevitable cast metal in which the free surface of the metal ("meniscus") placed in the refractory feed head first contacts the cooling wall of the mold after being injected into the mold. To start solidification, that is, a certain distance from the top edge of the copper component.

Thus, the solidification process begins in a hydrodynamically quiet environment, and the effect is that in conventional continuous casting, since turbulence caused by the inflow of molten metal remains confined within the buffer volume provided by the refractory feed head. It is to continuously cast semi-finished products of good metallurgical properties at much faster extraction rates.

In addition, it can be seen that this technique does not have any significant drawbacks with respect to conventional continuous casting and has been developed from conventional continuous casting and thus does not include any major technical steps. It is possible to convert a conventional continuous casting machine into a hot melt continuous casting machine without any difficulty, especially since the tundish is not rigidly connected to the mold, even if it lies a short distance above the casting machine. However, although the first publication of continuous castings of steels has made many known advances (more than 80% of the world's steel production is now produced by continuous casting), it is contemporaneous with a primer based on the industrial scope of vertical continuous casting. Continuous hot casting is still an area of research in the process of applying technology based on industrial scope.

Experiments conducted by the applicants revealed a major problem that could explain instability from the industrial point of view, i.e., instability during geometric time at the "cooled copper component / refractory feed head" interface. This is because this geometry is experienced due to the deformation of the upper end of the cooled component.

In conventional vertical continuous casting, such deformation is caused by an unexpected increase in liquid metal to a height that can overflow from the mold. This has little effect on the continuation of the casting process. In contrast, in continuous continuous casting, the situation is permanently similar to that of the "spill-over" type, since the meniscus is moved upstream of the cooled component. Deformation of the upper end of the copper component is unsatisfactory afterwards in that the desired solidification of the cast metal is initiated (penetration of molten metal under the feed head, poor coordination with the feed head, etc.).

It is an object of the present invention to in particular avoid any thermomechanical deformation of the upper end of the cooled component during casting.

To this end, the object of the present invention is to ensure peripheral solidification, in which the cast metal is in contact with the inner wall of the mold, with tubular metal components (copper or copper alloys) cooled in particular by the circulation of water with respect to the outer wall of the mold. Vertically of a metal, in particular steel, comprising an uncooled feed head made of thermally insulated refractory which is intended to contain molten metal at the top of the cooled metal component and defines a continuous sizing passage for the cast metal. In a mold for continuous casting of hot water, a metal annular portion cooled by circulation of an annular portion of a coolant is added between a metal component and the feed head, and an inner wall of the annular portion exhibits continuous characteristics of passages provided to the cast metal by the mold. Tubular metal spheres without any breakage between the annulus and the tubular metal component to satisfy It characterized by having a solid wall in alignment with the element.

Preferably, the annular portion is made of the same metal as the cooled tubular component, ie made of copper or a copper alloy.

Also preferably, this annular portion is mounted to be removable and can be easily replaced.

According to various advantages of the invention, the annular portion comprises an internal cooling circulation consisting of an annular chamber for circulation of the coolant, which chamber moves along the periphery of the mold and also preferably the inner wall of the annular portion immediately near this wall.

As is already clearly understood, the present invention has the inherent property of inserting a cooling body (an annulus) between the mold tube and the refractory feed head which organizes the expansion of the main tubular component, the cooling body being made of the same material. Although manufactured but have a magnetic cooling circuit, the relatively small height (relative to the height of the tube) is much higher than the height provided by the cooling system for the tube, in the end region of the cooling body, especially at the upper end facing the feed head. Allows for a great cooling effect. To be more specific, the tubes of continuous casting molds are usually 0.7 to 1.0 m in length, while the annular part according to the invention has a height of, for example, 4 to 10 cm.

From the point of view of the casting process, this moves the solidification start plane up to the upper end of the annular portion. In other words, in order to fulfill the solidification initiation function, the cooled tubular component of the mold is preferably replaced with a removable and cooled autonomous annular portion, but the cooling effect at the end, of course, of the main tubular component of the mold Since it is small compared to the height, it is more effective to incorporate therein a sheet of cooling water that circulates horizontally rather than vertically.

In this regard, in fact, a cooling circuit (at the end) relating to the need to ensure that the overall working height is excessively cooled in the first place in order to extract the significant total heat flux imposed by the progress of peripheral solidification of the cast metal traveling the entire length. The technical problem of a water jacket connecting two chambers is, in turn, that there is a limit to preventing deformation of the end of the tube if the temperature at this point rises to the temperature of the molten steel.

The present invention overcomes the obstacles by an additional body that is overcooled but has a small height so as to incorporate the horizontal circulation of the coolant therein, the upper contacting the refractory feed head to avoid deformation in contact with the molten metal. It is ensured to effectively cool both the upper end of the tube of the mold in intimate contact via the edge and the lower surface.

In view of the following description given by the method of the embodiment with reference to the attached single plate drawing, the invention will be clearly understood and other aspects and advantages will become more clearly apparent.

1 is a schematic vertical cross-sectional view of the top of a machine for vertical hot dip continuous casting of steel according to a known prior art general design;

2 is a partially enlarged view of a top part of a machine of the type described above, except that the design according to the invention is shown in detail.

In the drawings, like elements are referred to by like reference numerals.

Referring to the general view of FIG. 1, the upper part of a machine for continuous vertical squeeze casting of steel is provided with an outlet orifice (or an outlet orifice extending from the extraction direction of the metal to be produced, i. It can be seen that it consists of a tundish 1 comprising a bath of molten metal 2 which is conveyed by means of several outlet orifices to a mold 3 placed below it.

As shown, the mold comprises a tubular copper component 4 which is actively cooled by the circulation of water over the entire length of the outer surface of the tubular copper component. Conventionally, a steel liner 5 is provided for this purpose at a short distance from the tube 4 to channel the vertical sheet 21 of circulating water. The liner 5 has openings 22 at its ends that allow the sheet 21 of water to be in communication with the inlet chamber 6 and the discharge chamber 7, which chambers the liner 5 at some distance therefrom. The limit is defined by the surrounding casing 8.

On top of the inner tubular component 4 is a feed head 9 made of uncooled refractory, with the inner wall preferably arranged with the inner wall of the body 4 (in some cases irreversible) ).

In the context of the casting process, the arrangement of "cooled component 4 lying on insulated refractory feed head 9" defines a sizing passage for the cast metal, with the top 12 of the passage in the feed head being driven into the mold. It consists of a buffer region which limits the hydrodynamic disturbance caused by the arrival of the flow part 11 of molten metal, and the lower part 13 of the passage extending the feed head is the solidification region of the cast metal.

As shown, this solidification starts from the first contact of the cast metal with the inner wall of the cooled copper body 4, ie along the upper edge 14 of the wall, and grows from the periphery into the center of the solid shell. Continue forming (15) downward. Upon leaving the mold, the shell 15, having a thickness a little thicker than 1 cm, is strong enough to withstand the ferrostatic pressure of the stationary liquid core 24 and a water jet located at the bottom half of the machine, although not shown. Under the influence of the unit it continues to grow by its centripetal force until the semi-finished product 10 is completely solidified. Once the semi-finished product has solidified completely, it is cut into portions of a predetermined length (billets, blueum or slabs, depending on the shape of the casting cross section) and these portions are then available for a series of forming processes (rolling, etc.) Do.

With particular reference to FIG. 2, according to the invention an annular part 16 is located on top of the tubular component 4, which extends aft and is made of a copper alloy and cooled by a magnetic cooling system. In the example described, the aft consists of a chamber 17 running along the solid inner wall 18 of the annular portion at a short distance from the annular portion. The chamber is circular in shape and has an inlet and an outlet close to each other on either side of the partition wall closing the chamber. Therefore, a cooling circulation in the form of a horizontal annular portion occurs, and a horizontal circulation of a coolant (for example, water) surrounding the annular portion and the cast product is established.

In the figure, only the coolant inlet nozzle 19 and outlet nozzle 19 ′ connecting the circulation chamber 17 to the outer surface are shown.

The cooled annular portion 16 is directed towards the base in order to match well with the upper surface of the component 4 on which it rests and to avoid any risk of penetration of molten metal.

The cooled metal assembly formed by the annular portion 16 and the tubular component 4 constitutes the actual “active” portion of the mold. From the point of view of the cast metal, these two components are paralleled without any breakage between them, because the solidification of the cast metal starts and continues to grow as the cast product 15 proceeds downwards into the interior of this assembly. It acts as a component. The starting plane of this solidification is not the plane passing through the upper edge 14 of the component 4 but the plane passing through the upper edge 23 of the toroid 16.

Located at the top of this assembly 16-4 is a thermally insulating feed head 9, as already shown.

According to certain embodiments of the invention, this feed head 9 itself is also formed by two overlapping separating components:

Because of preventing any premature pseudo solidification of the cast metal in the alternating current region 12, the upper bush 25 made of refractory is selected for thermal insulation properties. The optional material may be fibrous refractory, a material sold under the trade name A 120K of the French company KAPYROK; And

In the vicinity of the crystallizer 4-16, when the entire assembly undergoes the normal vertical oscillation motion necessary for the success of the casting process, the thermomechanical stress of the machine operating in the thermal cycle is inevitably continuous in the casting process. When added by properties, the lower component (ring, 26) is made of a refractory adopted for good mechanical strength, since mechanical corrosion at the upper tip of the solid shell 15 on the edge 23 is prevented as possible. do. Materials such as SIAlON (Sialon), preferably doped with boron nitride, will be fully suitable.

Preferably, a circuit for injecting waste inert gas (for example argon) is provided between the feed head 9 and the metal assembly 16-4.

This circuit is made at the feed head 9 / metal assembly 16-4 interface and appears at one end around the inner periphery of the mold and is itself connected to a source of pressurized argon, although not shown at its other end. It is connected to the plenum chamber 29 to which argon is supplied via the nozzle 30 whose aperture is measured.

The benefit of the feed head made as two overlapping parts is that it can improve the mechanical strength of the underlying parts susceptible to corrosion caused by the "back and forth" motion of the solidified adjacent tip of the cast metal, which is a vertical vibration of the mold. to be.

On the other hand, this strong lower ring 26 is a smaller thermal insulator than the upper part. The cast metal may form an early pseudocoagulated film at the point of contact between the aligned inner wall 27 and the inner wall of the cooled annular portion 16. This film is the main source of heterogeneity with respect to the controlled solidification process in the cooled metal assembly 16-4. This, according to an advantageous embodiment already known elsewhere in the present invention (FR-A-93 03871), breaks the film of pseudo-solidification in which the curtain of argon is formed on the ring 26 and also uniformly cools the cast metal. This is because it is blown from the base of the feed head 9 for the purpose of starting to solidify in a rapid manner in contact with the annular portion 16 that has been made.

The basic advantage of the present invention is that since the upper part of the most stressed mold is made in the form of an additional piece (annular part, 16), under the economic conditions that this part requires and is compatible with the industrial implementation of continuous melt casting. It has been understood that it can be easily replaced with a new piece, and in some cases the inner tubular component 4 is not replaced.

According to another advantageous embodiment, the tendency of the shell 15 to adhere to the walls of the mold is reduced by the addition of known lubricants, and the injection of lubricants through the copper component 4 (FR-A-91 01551) and an ultrasonic transducer applied at the free end of the upper return 32 of the cooled component 4 to cause this component to vibrate. Such a transducer may be of the type "piezoelectric".

There is no need for the direction of application of the ultrasonic waves to be inclined (see eg FIG. 2). Nevertheless, the warp application has the advantage of combining the vertical vibration effect with the horizontal vibration effect, both of which contribute to reducing the wear between the castings 10 in the mold.

More specifically, reference may be made to FR-A-89 07839.

It goes without saying that the invention is not limited to the examples described but that many modifications or equivalents extend so long as the essential features given in the appended claims are concerned.

In particular, the present invention applies to long products as well as flat products. Thus, the words used such as "annular part", "annular part" or "ring", etc., although they suggested a circular shape, had a mold consisting of a plate assembled with cooled inner tubular components ( For example, a slab or large bloom mold for continuous casting) should be understood from a more general perspective.

Likewise, the present invention applies to the continuous casting of not only steel but also any other continuously castable metal, especially metals having a lower melting point than steel, such as aluminum or copper.

Claims (8)

As said component, it is intended to contain a cast tubular metal component which is intended to ensure solidification of the surroundings where the cast metal is in contact with the inner wall of the mold and is located in the liquid phase at the top of the cooled metal component. In a continuous casting mold for continuous vertical casting of metal comprising an uncooled feed head made of thermally insulating refractory defining a continuous sizing passage for a cast metal, the metal annular portion cooled by annular internal circulation of a coolant ( 16 is added between the cooled tubular metal component 4 and the heat insulating feed head 9, the inner wall 26 of the annular portion being solid and the continuous nature of the passages provided to the casting metal 10 by the mold. And the mold is arranged without any breakage between the annular portion and the tubular metal component so as to satisfy. The mold according to claim 1, wherein the cooled metal annular portion (16) is made of the same metal as the tubular metal component (4). The mold according to claim 1, wherein the cooled metal annular portion (16) has a height of about 4 to 10 cm. Mold according to claim 1, characterized in that the annular portion (16) is removably mounted to the tubular metal component (4). 4. The annular portion (16) according to claim 1 or 3, wherein the annular portion (16) comprises an internal cooling circuit consisting of a chamber (17) for horizontal circulation of coolant, wherein the chamber moves along the inner wall (18) of the annular portion around the mold. Molding characterized in that. 2. The refractory feed head 9 according to claim 1 comprises two overlapping separating components: an upper bush 25 made of refractory with good thermal insulation and a lower ring 26 made of refractory with good mechanical strength. Mold, characterized in that consisting of. The mold according to claim 1 or 6, comprising a circuit (28, 29, 30) for injecting an inert gas around the inner periphery of the mold between the feed head 9 and the annular portion 16. . Mold according to claim 1, characterized in that an ultrasonic transducer (31) is provided at the end of the upper revolving portion (32) of the tubular metal component (4) and intended to vibrate the mold.