KR20000005254A - Ingot mold for continuous vertical molding of metal - Google Patents

Abstract

PURPOSE: An ingot mold is provided to make the fuzzy gas injecting speed evenly and regularly react to the whole circumference of the mold during molding process. CONSTITUTION: The ingot mold has:a cooled copper or copper alloy body(1); a fire-tolerant supply bush(2) installed on the upper part of the cooled copper or the copper alloy; a sweeping slot(8) placed on the boundary of the bush(2) to inject inactive waste gas into the ingot mold; a distribution chamber(13) placed in the inner side of the ingot mold to supply slots; a chamber to supply gas by a diverging pipe(12) to connect the chamber with a pressurized gas source(20); and an injection slot(8) separated by a separation piece(21) to divide adjacent divided chambers(13'-13") extended along the circumference of the ingot mold.

Description

Ingot molds for continuous vertical casting of metal

The present invention relates to the vertical casting continuous casting of metals, especially steel.

Vertical hot melt continuous casting is essentially distinguished from conventional vertical continuous casting because the casting metal is subjected to ambient solidification on top of the cooled mold body (generally made of copper or copper alloy). The feed head is made of a refractory material comprising a reservoir of molten metal held in a liquid state. In this way, the point in the copper body where the cast metal starts to solidify is separated from the point where the free surface of the molten metal in the feed head lies, but they ultimately coincide with conventional vertical continuous casting.

The purpose is to cast good quality products with high extraction rates since the solidification zone is no longer disturbed by conventional turbulence in the flow of metal reaching into the mold and this turbulence is limited to the buffer volume in the feed head.

It is also known to use an inert gas purge, for example an argon purge, by injecting exhaust gas into the interface between the template and the feed head. Such an arrangement has been described, for example, in the name of the applicant in EP-A-620,062 patent application. This purge is intended to break the film of inhomogeneous spurious solidification, which tends to form when molten metal contacts the walls of the refractory feed head. This creates a suitable condition for the casting metal which starts solidification in a clear and uniform manner at the same point in the mold, ie at the same level as the upper edge of the cooled metal body at the end of the feed head.

The foregoing document describes the implantation technique shown in the accompanying Figure 1. It essentially comprises an annular slit 8 which appears around the inside of the mold, which is continuous or partial. Flowing along the purge slit 8 is the flow of waste argon from the annular plenum chamber 13 made near the slit and ensures that the same gas pressure is maintained at all points in the periphery in the chamber. Low-pressure-drop inlets 12 connect this chamber 13 to a gas supply consisting of a box 10 attached to a mold.

In this type of configuration, the major pressure drop in the flow of injected gas occurs in the purge slit 8 and is closely related to the geometry of the purge slots, moreover the thickness of the slit. If the surfaces facing each other (the upper face of the cooled metal body 1 of the mold and the lower face of the refractory feed head 2) are not exactly parallel, then the local variation in the slit thickness causes the inhomogeneous argon injection rate to the mold periphery. And surface defects on the cast product. Such inaccurate parallelism between two opposing surfaces is especially true when the casting is in the periphery, or when the cross section is large (slab or large bloom) and when the differential thermal expansion effect between the various metals present, moreover, occurs near the corner of the mold (decades) This always happens especially after casting.

The object of the present invention is to ensure that the purge gas injection rate acts uniformly and uniformly over the entire periphery of the mold during the casting process.

For this purpose, the object of the present invention consists of a cooled metal template in which a feed head made of refractory is defined and also a purge slit made at the interface between the body and the feed head and which is inert A continuous vertical pressurization of metal, in which the flow of waste gas is made close to the slit via the slit and injected into the inner periphery of the pressurized gas supply from the annular plenum chamber where the gas is supplied by itself via an inlet connected to the chamber. In a quiet mold, the purge slit is divided into a mold periphery with the aid of separating means for further dividing the plenum chamber into adjacent compartments of the mold periphery, and a graduated inlet is formed in each compartment formed to connect the compartment to the pressurized gas supply. It is characterized by being provided.

As will be appreciated, the present invention is provided to the discontinuous injection slit at the mold periphery as a flow of purge gas through the chamber, the chamber turning itself around the mold and divided itself into independent compartments. In this way, a plurality of autonomous injection circuits are produced from the pressurized gas supply, which are mounted in parallel and each flows into a compartment extended by a purge slit which supplies only one area of the periphery of the mold as gas. Including a graduated inlet, the parallel slits along their length ensure that the gas is distributed around the entire interior of the mold.

Preferably, the slit length is equal to the length of the connected compartment.

Thus, in any circuit due to external causes, for example, the abrupt narrowing of the purge slit, the disturbance of gas flow never affects the flow in neighboring circuits. Overall, the immediate periphery of the mold becomes insensitive to local breakdown, and local deformation in the purge slit may cause deterioration of gas flow characteristics around the periphery that is substantially larger than the periphery directly involved by incidental events. In contrast to the prior art.

The invention will be more clearly understood and other aspects and advantages will become more apparent in light of the attached plate drawings below.

1 is a vertical sectional view of a top of a vertical hot water continuous casting mold provided with a gas injection circuit according to the prior art described above.

FIG. 2 is an enlarged view of the top of a vertical hot water continuous casting mold according to the present invention, provided with a gas injection circuit, in a vertical section of plane B-B 'of FIG.

3 shows the injection circuit shown by cutting plane A-A 'of FIG.

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

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is only briefly described in order to illustrate the invention. Those skilled in the art will find a more detailed description of the complete structure of a vertical hot melt continuous casting mold, if desired, for example, with reference to EP-A-620,052 or the first mentioned FR-A-2,000,365.

This figure consists of tubular components made of copper alloy and the outer surface 16 is actively cooled by water circulation, while the inner surface where the molten steel 4 is in contact with the cold wall 17. (17) The casting space for solidifying and shaping the shell 15 is indicated by 1 as the upper end of the cooled metal body of the mold. This shell 15 forms a casing which occurs internally when the cast metal is extracted downwards from the mold and continues to complete solidification of the product due to the influence of the water spraying device installed in the casting machine in the lower section of the mold.

Molten metal is injected into the mold at a rate adjusted to the rate at which the cast metal can be removed, with the aid of a refractory nozzle that acts as a lower portion of the injection tundish, not shown but placed on top of the mold. The nozzle is provided at the bottom with side holes 6 and molten metal overflows into the mold via the side holes. In casting, the free surface 7 of the molten metal is kept at a controlled height about 10 cm above the hole 6 to control the outflow of the "metal" (consider the fluctuation due to the vertical vibration of the mold).

As will be understood, this upper portion of the cast metal (15-20 cm below the meniscus) is not actually contained in the copper body 16 but in the refractory feed head 2 located on the copper body 16. And a reservoir of molten metal aligned with the inner wall 17 of the copper body. In particular, this is the form that constitutes the main features of the hot dip casting according to the invention. In fact, the unavoidable turbulence that occurs in the volume of the cast metal in the region of the exit hole 6 is limited because part of the casting space is defined by the feed head. Therefore, the conditions of hydrodynamics are very suitable because solidification of the metal starts against the cooled copper wall 17 and at that point the outflow of the metal is of the "plug outflow" type (no substantial velocity component in the cross section of the product). Solidification of the metal continues.

However, a flow of inert purge gas (argon) is recommended throughout the inner periphery of the upper mold to the upper edge bar of the copper body where solidification begins. This purge flow allows an active and uniform start of the solidification process, by means of breaking the pseudo-coagulated film in a disordered and irregular shape with respect to the fire-resistant wall of the feed head 2, the fragment of which is referred to by reference number 14 Has been shown.

As shown, this purge flow is generated by a feed circuit comprising a graduated inlet 12 from the supply 10 of pressurized argon, with a scale between the feed head 2 and the body at the center. The engraved inlet connects this supply with the inner plenum chamber 13, which arises from the slit 8 which moves along the periphery of the mold and appears in the mold.

In the embodiment shown in the figure, this slit is made by a graduated wedge 9 inserted into the periphery of the copper component 1 between the two components described above.

2 and 3 according to the invention, it can be seen that there is a solution provided for the problem lying in the purge circuit in relation to the uniform delivery of the output effluent of the gas inside the mold.

Employs a configuration comprising two chambers in a cascade,

Zone the second chamber into compartments parallel to the periphery of the mold, in which the purge slit is also coupled in this way.

The first chamber 20 serves to contain a volume of argon at a given pressure. As indicated, the graduated inlet 12 connects this chamber with the second chamber 13, the function of the second chamber being to carry the gas to the purge slit 8, the purge slit being the periphery of the mold On the inner surface 17 of the mold 1.

The purge slit 8 is divided into regions in parallel, partition walls which divide the second plenum chamber 13 into compartments 13 ′, 13 ″ in parallel around the periphery of the mold and coincide with the position of the slit. They are separated from each other by 21. For this purpose, each partition wall 21 is divided into a low height vane 21a and also a mother portion 21b corresponding to the thickness of the slit 8 in which it is located. And the surface of the parent portion corresponds to the cross section of the chamber to be divided.

Each partition wall 21 is preferably a machined piece that is attached to the chamber 13 between two air inlets of a welded graduated inlet 12 ′, 12 ″, for example.

A plurality of autonomous circuits for transporting the gas into the mold are thus produced, which are mounted "parallel" in relation to a single supply, represented by the pressure chamber 20 and extend downwards by the area 8 of the slit and are generally Each consists of a compartment 13 'fed through a graduated inlet 12' finished from the chamber 20. The inlet is sized to ensure that the gas pressure around the periphery of the mold is uniform. With respect to the intermediate chamber 13, the division into individual compartments 13 ′, 13 ″, which are respectively associated with respective regions 8 ′, 8 ″ of the slit 8, is formed for each individual circuit 12 ′-13 ′ -8 formed. Ensure uniform gas injection.

The introduction of the division according to the invention makes it possible to influence the local variation in the thickness of the slit on the total flow rate of the gas injected into the mold to break into five or eight elements. In other words, by dividing the "downstream" portion of the injection circuit according to the invention, each device circuit formed is fed in the same way as a regular method by a general pressurized chamber 20 and the entire assembly is changed in local slit thickness. It is not sensitive to, and more generally, not sensitive to any localized perturbation of the injection circuit due to the outside of the circuit.

Thus, it is possible to inert gas throughout the large mold perimeter length (a few meters in length) through a uniform method. These results illustrate in particular the advantages that can be obtained by applying the present invention to continuous casting of large format products (slab or bloom).

It is needless to say that the invention is not limited to the described embodiments, but many variations or equivalents, as long as the definition given by the appended claims is considered.

In particular, the graduated inlet 12 can also be configured in the form of a slit.

Likewise, it does not matter whether the intermediate chamber 13 enters the refractory feed head 2 (see FIG. 1) or into the copper component 1 (see FIGS. 2 and 3). Of course, it is desirable to seal the circuits and chambers that have entered the refractory components.

With regard to the partition wall 21 which doors the slit 8 and the chamber 13, it is quite clear that any means other than those described for performing this dual function are suitable for dividing the chamber 13, like a plate. These plates are combined with the refractory portion of the top of the ribs to engage the ribs (equivalent to 21a) made on the upper surface of the copper component and to define the slits, the order of the thickness sizes of the purge slits being about 0.1 to 0.3 May be mm.

Claims (6)

Consisting of a cooled metal template on which a feed head made of refractory for casting metal is defined, and a purge slit fabricated at the interface between the body and the feed head, the flow of waste inert gas In a mold for continuous vertical casting of metal, which is injected around the inner periphery of an annular plenum chamber, which is made close to the slit via a gas and is supplied by itself via an inlet connecting the chamber to a pressurized gas supply. Inlet (12) divided and graduated around the mold periphery by means of separating means (21) which also divide the plenum chamber (13) into adjacent compartments (13 ', 13 ", etc.) around the periphery of the mold. 12 ", etc.) are provided in each compartment formed so that a compartment may be connected to the pressurized gas supply part 20, The mold. The forced ventilation chamber (13) according to claim 1, wherein the forced ventilation chamber (13) is made in the cooled metal body (1) of the mold and the separating means has a front portion (21a) and a plenum chamber (13) for dividing the slit (8). A mold characterized by a partition wall (21) comprising a mother portion (21b) for dividing. The mold according to claim 1 or 2, characterized in that the length of each region (8 ', 8 ", etc.) of the slit (8) is equal to the length of the compartment (12', 12", etc.) to which it is coupled. The mold according to claim 1, wherein the graduated inlets (12 ', 12 ", etc.) are also configured in the form of slits. Mold according to claim 1, characterized in that the purge slit (8) has a thickness of 0.1 to 0.3 mm. The mold according to claim 1, wherein the mold is installed in a machine for continuous casting of steel.