Continuous Casting Mold Having A Breakout Sensing And Control Device

Abstract

The invention relates to an apparatus to be used at a continuous casting plant for preventing the results of a break through of the solidifying bar. Such apparatus comprises a protective body which is resistant against liquid metal and immediately below the mould surrounds the bar shell over at least part of its circumference and is provided with a cavity open towards the bar shell for receiving liquid metal, and in said body a sensor connected with an alarm system for indicating a metal break through so that casting may be interrupted.

Description

The invention relates to an apparatus at a continuous casting plant, in particular at a plant for continuous casting of steel, in which a bar having a liquid core and a solidified bar shell is drawn out of a water-cooled mould.

In continuous casting of hot liquid metals, in particular in continuous casting of steel bars, sometimes the liquid metal breaks through the already solidified bar shell, as a rule immediately below the mould in the area of a relatively narrow circumferential zone of the cast bar. By regulating the casting speed, cooling of the bar and measuring the bar shell thickness, a high operational safety may be obtained in a continuous casting plant so that the number of breaks through will remain small; however, such an occurrence is a great nuisance and therefore feared because when the metal breaks through the plant parts below the continuous casting mould, such as supporting and guiding rollers, supporting construction parts and the like are damaged as the metal welds with these parts. Frequently it is necessary to remove the supporting and guiding structures in the vicinity of the mould, as well as the arrangement for cooling the bar, and to replace them by new parts, which means that the whole plant has to stand still up to a time of 24 hours. So far it has not been possible to provide for an apparatus that would prevent such results of a break through.

The invention is aimed at avoiding the described disadvantages. It is aimed at providing at a continuous casting plant a safety device for preventing damages when a metal break through occurs. According to the invention this task is solved by a protective body which immediately below the mould surrounds at least part of the circumference of the cast bar shell, said body being resistant against the liquid metal and provided with a cavity open towards the bar shell for receiving liquid metal and in which a sensor is housed which indicates a metal break through.

Advantageously the protective body is releasably attached to the mould.

The protective body may comprise several parts which are, if desired, cooled by circulation of a coolant agent, of which always two parts lying opposite to each other with regard to the bar, are displaceable against each other so that they may be adapted to different bar cross sections.

In a plant for producing wide slabs it is sufficient that the protective body comprises two parts arranged to lie opposite to each other and adapted to be adjusted only to the broad sides of the slabs, the cavities at their sides being bordered by walls adjacent to the margin of the bar shell.

Preferably the protective body is provided at least at its lower edge with a supporting plane for the bar shell, which is preferably formed by a hollow section cooled by circulation of cooling water.

A further embodiment of the invention resides in that the cavity of the protective body is provided with a lateral opening through which liquid steel may issue into a collecting vessel.

The sensor for indicating the break through of metal may be made of a metal wire electrically insulated against the protective body and against the bar, which wire is connected with one pole of a power supply; further, an alarm signal is provided which is electrically connected with the other pole of the power supply and with the mould or with the protective body, so that in case of a metal break through the insulation of the metal wire is destroyed and an electrically conductive connection is established between the metal wire and the protective body or via the bar with the mould, and the alarm signal is actuated.

In order that the invention may be more fully understood, several embodiments thereof shall now be explained with reference to the accompanying drawings.

FIG. 1 is a vertical sectional view of a continuous casting mould provided with a device according to the invention showing the supporting and guiding structure for the bar to be drawn out.

FIG. 2 is a schematical illustration of the device indicating the breakthrough of steel.

FIGS. 3a and 3b show different embodiments of the metallic protective body in sectional views;

FIG. 4 is a horizontal sectional view of a metallic protective body according to the invention used for broad slabs and

FIG. 5 shows a detail regarding the formation and mounting of the device according to the invention for indicating the break through of steel.

In FIG. 1 numeral 1 denotes a water-cooled mould of copper, from which a steel bar 2 with a liquid core 3 and an already solidified cast bar shell 4 is drawn out over supporting and guiding rollers 5, 6 by means of a not illustrated drawing out device. On both sides of the bar spraying nozzles 7 are provided for cooling the cast bar 4 with water. The supporting and guiding rollers 6 may be mounted in a (not illustrated) stand, while the supporting and guiding rollers 5 are mounted by a holding means 8 at the lower edge 9 of the mould 1 oscillating in direction of the bar axis; the rollers 5 oscillate with the mould. According to the invention a metallic protective body 10 surrounds the bar circumference between the rollers 5 and the mould 1. Suitably the body is releasably mounted at the mould 1 by means of a holding ring 11. The protective body 10 is formed as a hollow body, whose hollow space 12 is in connection with a not illustrated water supply and water drain. In the illustrated example the protective body 10 has an about C-shaped cross section, whereby an upper and a lower cooled supporting plane 13, 14 for the bar shell 4 is formed, between which a cavity 15 extends which is open towards the bar shell 4. Into this cavity 15 surrounding the bar 2, a wire 16 insulated against the metallic protective body 10 and the bar 2 is inserted; that part thereof which is guided out of the protective body 10 through a bore is denoted with 16'. This part 16' is connected with an electrical alarm signal whose system is illustrated in FIG. 2. The wire 16 present in the cavity 15 comprises, as shown in detail in FIG. 2, a metal wire 17 and an electrical insulation 18. The electrical insulation 18 may surround the wire 17 only where it is in contact with the protective body 10, as illustrated in FIG. 5. It may, however, also surround the wire 17 over its entire cross section. The insulation is to be resistant against the radiation heat of the bar 2 and -- if it surrounds the wire entirely -- has to be destroyed upon contact with liquid steel, which may take place either by breaking as a result of heat tensions or by melting.

The metal wire 17 is connected via a line 17' and a safety fuse 19 with one pole of a power supply 20, e.g., alternating current of 42 volt tension. The other pole of the power supply 20 is connected via a line 21 and a safety fuse 22 with an alarm signal 23, e.g., an audible alarm, a blinker or the like. The alarm signal 23 is conductively connected with the mass, i.e., with the mould 1 or with the metallic protective body 10. When the liquid steel 3 breaks through in the bar shell zone 4' (FIG. 1) where ruptures are most likely to occur as is known by experience, the steel is collected in the cavity 15 and an electrically conductive connection is established between the wire 17 and the protective body 10 or via the bar 2 itself to the mould 1, so that by closing the circuit 17, 17', 20, 21, 1 or 10, the alarm signal 23 is actuated. The casting process may then be interrupted by hand or by stopping the drive for drawing out the bar. It is also possible to connect a line 24 with a relay switched in parallel or contractor 25 so that a switch is actuated which closes or interrupts a current conduit 26 which is connected, e.g., with the drive motor of the bar drawing out means in a manner that at the moment when the alarm signal 23 is actuated the continuous casting plant is simultaneously brought to a standstill. Instead of the device illustrated in FIG. 2 also a thermal element or a radiation pyrometer may be used, which registers the temperature or light difference occurring when the bar breaks through, and thus causes in the same manner an electrical switching so as to stop the continuous casting plant.

When steel breaks through, the cavity 15 is entirely or partly filled with steel, which solidifies there. As the steel cannot flow off downwardly, neither the rollers 5,6 nor the spraying nozzles 7, nor the supporting stand arranged below can be damaged. The inner face of the protective body may be provided with a graphite layer or with another refractory layer so that the steel is prevented from welding with the protective body. The protective body may be used several times; only the insulated wire 16 has to be renewed.

Suitably the protective body is designed in several parts. When square bars are cast at each bar side a body is provided so that an annular closed cavity 15 is formed. The individual parts of the body may easily be removed after a bar rupture, so that the bar may be drawn out before its complete cooling, if desired after the broken steel was burnt off by means of a flame cutter. Also when slabs are produced, the body should be composed of several parts, so that also an adjustment and adaptation to various bar cross sections is possible.

According to FIG. 3a the metallic protective body may be composed of an upper part 27 made of full hematite cast iron and a lower part 28 made of copper; the lower part forms the lower supporting plane 14, which is a water-cooled hollow section; in this embodiment no upper supporting plane 13 is used. FIG. 3b shows a body made of a hematite cast body 27' and a copper hollow section 28 with a lateral opening 29 for draining liquid steel via a groove 30 into a container not illustrated, so that there is the possibility to receive the total amount of steel present above the ruptured place and to guide it away from the rollers 5, 6 or from the supporting construction.

In FIG. 4 numerals 31, 32 denote metallic protective bodies arranged at the broad sides of a rectangular slab bar 2, which bodies are provided with lateral walls 33 apposed to the edge of the bar shell 4, whereby closed cavities 34,35 are provided which contain electrically insulated wires 36,37; these wires are connected with a power supply 20 in the manner already described; when broad slabs are produced it is not necessary to provide protective bodies at the narrow sides, because there steel does not break through.

The cavities 15,34,35 may be connected with a conduit, not illustrated, through which a gas is supplied which may be used for cooling the bar shell area 4'; the supplied gas may flow off downwardly through the supporting plane 14 or through the opening 29. Suitably a non-oxidizing gas is used for this purpose, so that the formation of scale in the bar shell area 4' or deposits of scale in the cavities 15, 34,35 are prevented .

Claims

I claim:

1. An apparatus for use in a continuous casting plant for determining if the liquid core of the cast bar has broken through the outer shell of the bar, the apparatus being positioned adjacent the casting mould, comprising, a protective body resistant against liquid metal which is positioned immediately below the mould for minimizing the flow of any liquid metal that breaks through the outer shell of the bar onto other parts of the plant, the protective body surrounding the cast bar over at least that part of its circumference where break throughs normally occur and being provided with a cavity therein open toward the cast bar, system means for indicating a metal break through including, a sensor for detecting the presence of liquid metal, said sensor being positioned in the cavity and connected to the system means in a way as to cause the system means to indicate a metal break through when liquid metal is present in the cavity.

2. The apparatus set forth in claim 1, wherein the protective body is releasably attached to the mould.

3. The apparatus set forth in claim 1, wherein the protective body comprises at least two parts, said parts being displaceable relative to each other for adaptation to different bar cross sections.

4. The apparatus set forth in claim 3, wherein the parts of said body are cooled by circulation of a cooling agent therein.

5. The apparatus set forth in claim 1, wherein for producing a broad slab with two broad sides and two narrow sides the protective body comprises two parts, the two parts being positioned on the two opposite broad sides of the cast slab and each of the parts having a cavity therein open toward the slab.

6. The apparatus set forth in claim 1, wherein the protective body is provided at least at its lower edge with a supporting plane for the bar shell.

7. The apparatus set forth in claim 6, wherein said supporting plane is formed by a hollow section cooled by circulation of a cooling agent therein.

8. The apparatus set forth in claim 1, wherein the cavity of the protective body is provided with a lateral opening through which liquid steel may flow into a collecting vessel.

9. An apparatus for use in a continuous casting plant for determining if the liquid core of the cast bar has broken through the outer shell of the bar, the apparatus being positioned adjacent the casting mould, comprising:

a protective body resistant against liquid metal and positioned immediately below the mould, said protective body surrounding the cast bar over at least a part of its circumference and being provided with a cavity therein open toward the cast bar;

an alarm signal means with a first terminal connected to the mould;

a sensor for indicating the presence of liquid metal, said sensor being positioned in the cavity of said protective body and being made of a metal wire which is electrically insulated against the protective body and against the cast bar; and

a power supply with one pole connected to the wire and the other pole connected to a second terminal of said alarm signal means, whereby in case of a metal break through, the insulation of the metal wire is destroyed and an electrically conductive connection is established between the metal wire and, via the bar, with the mould, and the alarm signal means is actuated.

10. An apparatus for use in a continuous casting plant for determining if the liquid core of the cast bar has broken through the outer shell of the bar, the apparatus being positioned adjacent the casting mould, comprising:

a protective body resistant against liquid metal and positioned immediately below the mould, said protective body surrounding the cast bar over at least a part of its circumference and being provided with a cavity therein open toward the cast bar;

an alarm signal means with a first terminal connected to said protective body;

a sensor for indicating the presence of liquid metal, said sensor being positioned in the cavity of said protective body and being made of a metal wire which is electrically insulated against the protective body and against the cast bar; and

a power supply with one pole connected to the wire and the other pole connected to a second terminal of said alarm signal means, whereby in case of a metal break through, the insulation of the metal wire is destroyed and an electrically conductive connection is established between the metal wire and said protective body, and the alarm signal means is actuated.