KR100499192B1 - Mould for the vertical hot-top continuous casting of metals - Google Patents

Abstract

The mold has a cooled copper or copper alloy body 1, with a refractory feed head 2 mounted on top of the cooled copper or copper alloy body, injecting an inert waste gas stream into the inner surface of the mold at their interface. The slits 8 to be provided are provided. The slit is supplied by the distribution chamber 13 provided on the inner surface of the mold, which is in turn supplied with the gas by the inflow passage 12 connecting the chamber and the pressurized gas source 20. The injection slit 8 is separated by separating means 21 which divide the independent chamber along the periphery of the mold into adjacent compartments 13'- 13 "extending along the periphery of the mold, and into each compartment formed thereby. The abutment passage 12 is opened, thus obtaining a plurality of foundation systems 12'-13'-8 'mounted parallel to each other on a single pressure chamber 20, such as a local change in slot thickness. Local interference does not substantially affect the injection of gas into the periphery of the mold.

Description

Mold for continuous casting of metal vertical press {MOULD FOR THE VERTICAL HOT-TOP CONTINUOUS CASTING OF METALS}

The present invention relates to vertical hot-top continuous casting or meniscus free casting of metals, in particular steel.

Vertical hot melt continuous casting is made of refractory material that includes a reservoir of molten metal on top of a cooled mold body (typically made of copper or copper alloy) that solidifies the periphery of the cast metal. It is fundamentally different from conventional vertical continuous casting in that the feed head is arranged (see FR-A-2,000,365). In this method, the point in the copper mold body where the cast metal starts to solidify is separated from the point where the free surface of the molten metal is located in the feed head, but in conventional vertical continuous casting these two points are substantially coincident.

Its purpose is to cast high quality products at high release rates at high release rates, where the solidification zone is no longer obstructed by normal turbulence in the metal flow into the mold and these turbulences are volume).

It is also known to apply an inert gas purge, such as an argon purge, by injecting exhaust gas into the interface between the mold body and the feed head. Such a configuration is described, for example, in EP-A-620,062, the applicant's patent application. This purge serves to destroy the membrane of inhomogeneous spurious solidification that is likely to form when molten metal contacts the walls of the refractory feed head. Advantageous conditions are thereby achieved for the cast metal so that the cast metal always starts to solidify clearly and uniformly at the same point in the mold, ie at the same level as the upper edge of the cooled metal mold body at the end of the feed head.

The above-mentioned document describes the injection method shown in the accompanying Figure 1. It basically comprises an annular slit 8 which is open at the internal perimeter of the mold, which slit 8 is continuous or divided. The flow of waste argon from the annular plenum chamber 13 formed near the slit 8 flows along this purge slit 8 and at the same gas pressure at all points in the periphery of the chamber. To be maintained. Low-pressure-drop inlets 12 connect the chamber 13 to a gas supply consisting of a box 10 attached to a mold.

In this type of configuration, a main pressure drop in the injected gas flow occurs in the purge slit 8, which is related to the geometry of the purge slit, in particular the thickness of the slit. If the mutually opposing surfaces (the upper surface of the cooling metal mold body 1 and the lower surface of the refractory supply head 2) are not exactly parallel, the local variation in the slit thickness causes the inhomogeneous argon injection rate of the mold peripheral portion to become uneven. There is a risk of defects on the surface of the casting. This non-equilibrium between two mutually opposing surfaces, especially when the periphery or cross section of the casting is large (slab or large bloom), and the effect of the difference in thermal expansion between the various metals is near the corner of the mold. If it occurs (which always happens after casting moisture).

It is an object of the present invention to make the injection rate of purge gas uniform throughout the mold during the casting process.

1 is a vertical sectional view showing an upper portion of a vertical hot water continuous casting mold having a gas injection circuit according to the related art described above;

FIG. 2 is an enlarged vertical sectional view of the B-B plane of FIG. 3 showing an enlarged view of the gas injection circuit according to the present invention formed on the upper side of the vertical hot water continuous casting mold;

3 is a cross-sectional view illustrating the injection circuit by cutting the A-A surface of FIG. 2.

For this purpose, the object of the present invention is to define a passage for a casting metal and a cooled metal mold body on which a supply head made of refractory is placed, and a purge slit formed at the interface between the main body and the supply head. A flow of inert waste gas is injected from the annular plenum chamber formed near the slit through the slit around the inner circumference of the mold, and the plenum chamber is supplied with gas through an inlet connected to a pressurized gas supply unit. In a vertical pressure casting continuous casting mold of metal, the purge slit is similarly divided around the mold by separating means for dividing the plenum chamber into adjacent compartments along the inner circumference of the mold, and calibrated inlet. ) Is provided in each compartment to connect each compartment and the pressurized gas supply unit.

As can be seen below, the present invention basically forms a discontinuous injection slit around the mold over the inner circumference of the mold, and over the inner circumference of the mold through a chamber divided into mutually independent compartments along the inner circumference of the mold. Inject purge gas. In this way, a plurality of independent injection circuits from the pressurized gas supply are formed in parallel with each other, each injection circuit having a calibrated inlet, which is opened into the compartment and only one around the mold through the purge slit. The gas is supplied only to the portion of, and the gas is distributed to the entire inner circumference of the mold by arranging each slit in parallel.

The length of the slit is preferably equal to the length of the corresponding compartment.

Thus, the disruption of gas flow in any circuit due to external causes, such as the sudden narrowing of the purge slit, never affects the gas flow in neighboring circuits. Therefore, the area around the immediate injection of the mold is not subjected to local breakage, and in contrast, in the prior art, the characteristics of the gas flow due to the local abnormality of the purge slit in a portion larger than the portion directly related to the abnormality in the mold inner circumference Occurs.

The present invention and other features and advantages will be more clearly understood by the following description with reference to the accompanying drawings.

In each figure, like elements are denoted by like reference numerals.

1 is for briefly explaining the field of the present invention. Those skilled in the art will appreciate when a more detailed description of the complete structure of a vertical hot melt continuous casting mold is required, for example with reference to EP-A-620,052 or to FR-A-2,000,365 mentioned earlier.

1 shows an upper side of a cooled metal mold body 1, which is composed of tubular components made of a copper alloy, the outer surface 16 of which is forcedly cooled by water circulation. The inner wall 17, which is an inner side thereof, defines a casting space in which the molten steel 4 forms a shell 15 by contacting and solidifying thereto. This shell 15 forms a casing that grows inward when the cast metal is extracted downwards from the mold and continues until the product is completely solidified by a water jet mounted on a casting machine downstream of the mold. To grow.

Molten metal is injected into the mold at a rate suitable for the rate at which the cast metal is released from the mold by means of a refractory nozzle 5 which communicates with the bottom of an injection tundish (not shown) placed on top of the mold. The nozzle 5 has a lateral hole 6 at the bottom, through which the molten metal is introduced into the mold. During casting, it is possible to maintain the free surface 7 of the molten metal at a controlled height of about 10 cm above the hole 6 by controlling the flow of the "metal" (consider fluctuations due to the vertical vibration of the mold).

This upper portion of the cast metal (up to 15 to 20 cm below the meniscus) is located on the copper mold body 1, not on the copper mold body 1 and preferably on the inner wall 17 of the copper mold body It is formed in the refractory feed head 2 in alignment with the and serves as a reservoir for receiving molten metal. This is an important feature of the pressure casting in accordance with this invention. In practice, the inevitable turbulence occurring in the cast metal in the region of the outlet hole 6 is limited to a part of the casting space defined by the feed head. Therefore, since the flow of metal is in the "plug floe" form (there is no large velocity gradient in the cross-section of the casting), the solidification of the metal to the cooled copper inner wall 17 is under hydrodynamically favorable conditions. Start and grow.

However, it is desired that an inert gas (argon) for purge flow along the inner circumference of the mold just above the upper edge of the copper mold body from which solidification begins. This purge flow destroys pseudocoagulated membranes that form disorderly and irregularly with respect to the refractory wall of the feed head 2, so that coagulation starts accurately and uniformly, a fragment of which is shown at 14.

As shown, this purge flow is generated by a supply circuit comprising a correction inlet 12 from a supply 10 of pressurized argon, which correction inlet 12 is formed along the periphery of the supply and the mold. The supply is connected to an inner plenum chamber 13, with the slit 8 extending from the plenum chamber 13 opening into the mold between the supply head 2 and the body 1.

In the embodiment shown in the figure, these slits are formed between the two parts 1, 2 described above by means of a correction wedge 9 inserted along the periphery of the copper body 1.

Referring to Figures 2 and 3 according to the present invention, in connection with the uniform distribution of the flow rate of gas along the inner circumference of the mold, it can be seen that the solution to the problem of the purge circuit is as follows:

Employing a configuration comprising two chambers in cascade form,

The second chamber is divided into compartments parallel to the periphery of the mold, and the purging slits corresponding to this chamber are also divided in the same way.

The first chamber 20 serves to receive a certain amount of argon at a predetermined pressure. The correction inlet 12 connects the first chamber 20 to the second chamber 13, the function of which is to carry gas to the purge slit 8, as shown, The slit 8 is opened at the inner wall 17 of the mold 1 along the periphery of the mold.

The purge slit 8 is divided into parallel zones, each zone being arranged in parallel along the periphery of the mold and with a second plenum into compartments 13 ', 13 ", ... which match the position of the slit. They are separated from each other by partitions 21 which divide the chamber 13. For this purpose, each partition 21 is divided into a lower height of the front portion 21a corresponding to the thickness of the slit 8 in which it is located, and It consists of the mother part 21b which has the surface corresponding to the cross section of the chamber 13.

Each partition 21 is a machined part, and is preferably attached in the chamber 13, for example by welding, between two flow paths of the correction inflow passages 12 'and 12 ".

Thus, a plurality of independent circuits for delivering the gas into the mold are manufactured, which are mounted "parallel" with respect to a single supply represented by the pressure chamber 20 and the zone 8 'of the slit 8. And each into a compartment 13 ', which is supplied downstream through a correction inlet path 12' extending downstream from the common chamber 20. The chamber 20 is sized to ensure that the gas pressure around the mold is uniform. Each individual circuit formed by dividing the intermediate chamber 13 into individual compartments 13 ', 13 ", ... which are respectively coupled with specific zones 8', 8", ... of the slit 8 Uniform gas injection is ensured at (12'-13'-8 ').

The split introduction of the gas according to the invention makes it possible to split the influence of the local variation of the slit thickness on the total flow rate of the gas injected into the mold by dividing it by 1/5 or 1/8. In other words, in the present invention, by dividing the " downstream " portion of the injection circuit, a constant and identical gas is supplied from the common pressurization chamber 20 to each of the basic circuits thus formed, and the entire assembly is changed in the local thickness of the slit. Insensitive to, and more generally, insensitive to any local disturbance of the injection circuit due to factors external to the circuit.

Thus, it becomes possible to inject an inert gas uniformly over a large mold peripheral length (a few meters). Therefore, special advantages can be obtained by applying the present invention to continuous casting of large-shaped castings (slabs or blooms).

The present invention is not limited to the above embodiments, and of course, there are many variations or equivalents in view of the appended claims.

In particular, the correction inflow passage 12 itself may be configured in the form of a slit.

Likewise, forming the intermediate chamber 13 in the refractory supply head 2 (see FIG. 1) or in the copper body 1 (see FIGS. 2 and 3) is not a problem. Of course, the circuits and chambers formed in the refractory portion are preferably sealed.

The partition 21 for dividing both the slit 8 and the chamber 13 may be any means other than the above for performing this dual function, for example, a plate 21b capable of dividing the chamber 13. It can be replaced by means such as, such a plate is combined with ribs (equivalent of 21a) formed on the upper surface of the copper body and the refractory portion of the upper to define the slit, the thickness of the slit for purging is about 0.1 to 0.3 mm.

Claims (5)

A cooling metal mold body defining a passage for a cast metal and having a supply head made of refractory placed thereon, and a purge slit formed at an interface between the body and the supply head, wherein a flow of inert waste gas is near the slit. In the mold for continuous vertical casting of metal, which is injected into the circumference of the mold through the slit from the annular plenum chamber formed in the gas through the inlet path connected to the pressurized gas supply, The purge slit 8 is provided at the periphery of the mold by separating means 21 for dividing the plenum chamber 13 into mutually adjacent compartments 13 ', 13 ", ... along the inner circumference of the mold. Similarly divided, a mold characterized in that a correction inflow passage (12 ', 12 ", ...) is provided in each compartment to connect each compartment and the pressurized gas supply part (20). 2. The plenum chamber (13) according to claim 1, wherein the plenum chamber (13) is formed in a cooled metal mold body (1), and the separating means is provided with a front portion (21a) and a plenum chamber (13) for dividing the slit (8). A mold, characterized in that the partition (21) comprising a mother portion (21b) for dividing. The length of each zone 8 ', 8 ", ... of the slit 8 is the same as the length of the corresponding compartment 13', 13", ...). Molding characterized in that. The mold according to claim 1, wherein the correction inflow passages (12 ', 12 ", ...) are also configured in the form of slits. The mold according to claim 1, wherein the purge slit (8) has a thickness of 0.1 to 0.3 mm.