JP6819618B2 - Method of preventing molten metal from scattering in a continuous casting machine - Google Patents

Description

According to the present invention, in a continuous casting operation of a molten metal such as molten steel, when a breakout occurs, the molten metal in the continuous casting machine is used to suppress damage to the continuous casting machine equipment due to scattering of the molten metal that has flowed out. Regarding the shatterproof method.

When continuous casting of molten steel using an internal water-cooled mold that is open up and down, mold powder is added to the mold for the purpose of lubricating the solidified shell to be generated and the mold and preventing air oxidation of the molten steel. This mold powder flows into the gap between the solidified shell and the mold to form a mold powder film layer, and is responsible for lubricating the solidified shell and the mold. If the inflow of mold powder is insufficient due to changes in the components of the mold powder, changes in melting characteristics due to it, or insufficient supply, lubrication by the mold powder will be insufficient, and the solidified shell and the mold will be connected. So-called restrictive breakout occurs due to seizure.

In addition to breakout due to seizure due to poor inflow of mold powder, the high temperature of the molten steel and the entry of foreign matter between the solidified shell and the mold cause a delay in solidification of the solidified shell, resulting in a local solidification shell thickness. A thin portion is formed, and a breakout may occur due to the thin portion of the solidified shell breaking under the mold due to the static pressure of the unsolidified molten steel.

In continuous casting of molten steel, for example, when a breakout occurs directly under the mold, the molten steel flowing out from the solidified shell adheres to the rolls and roll bearings of the support roll segment installed directly under the mold, and is below the support roll segment. It flows down toward the installed guide roll segment. The molten steel adhering to the support rolls, guide rolls and roll bearings solidifies, and the rolls become non-rotatable due to the massive objects (called "bare metal") formed by the solidification of the molten steel. Therefore, the support roll segment and the guide roll segment, which have rolls on which molten steel adheres and cannot rotate, cannot be used, and replacement work is required for restoration.

The wider the scattered range of the spilled molten steel, the more roll segments need to be replaced and the longer the restoration work. Here, the roll segment is a facility equipped with a plurality of pairs of slab support rolls, and a roll segment composed of a support roll (a slab support roll having a relatively small diameter directly under the mold) is called a support roll segment. , A roll segment composed of a guide roll (larger in diameter than the support roll) installed on the downstream side in the casting direction of the support roll is called a guide roll segment. The continuous casting machine is provided with a plurality of guide roll segments, and is called in the order of the first guide roll segment, the second guide roll segment, ..., The nth guide roll segment from the upstream side in the casting direction.

Numerous proposals have been made to narrow the scattering range of the spilled molten steel. For example, in Patent Document 1, a protector having a flow-down suppressing member (expanded metal or the like) capable of draining water and having a rotating roller at the lower end is attached inside a support roll segment of a continuous casting machine, and the rotating roller is attached. A bullion outflow prevention device has been proposed in which the short side surface of a slab slab is brought into contact with a predetermined pressure.

Further, in Patent Document 2, during continuous casting, a cooling medium is sprayed on the molten steel leaked from the slab due to breakout through the ejection port of the cooling nozzle along the outer surface of the slab, and the leaked molten steel is crushed. A method has been proposed.

Japanese Unexamined Patent Publication No. 6-99258 JP-A-2007-245213

However, the above-mentioned prior art has the following problems.

That is, in Patent Document 1, the oxide scale generated on the surface of the solidified shell closes the gap of the flow suppression member installed in the protector and is deposited on the flow suppression member. Therefore, in order to achieve the desired flow control during the outflow of the bullion, it is necessary to periodically remove the sediment from the flow control member. In addition, the deposits on the flow control member may fall from the flow control member due to the influence of cooling water that cools the slab, and the dropped deposits enter the gap between the slab support roll and the slab. Has a problem that it leads to a scratch on the surface of the slab.

Further, in Patent Document 2, it is necessary to operate a booster pump in order to obtain an ultra-high cooling water ejection speed, and even a continuous casting machine provided with a breakout detection sensor may not be able to detect breakout. Therefore, it is necessary to keep the booster pump running at all times to ensure that the molten steel leaking from the slab due to breakout is crushed. That is, energy loss is caused by the constant operation of the booster pump. In addition, the position of the bullion outflow due to breakout cannot be specified in the mold width direction. Therefore, even when the breakout that occurs directly under the mold is targeted, the spout of the cooling nozzle is installed in the entire mold width direction. There is also the problem that it is necessary and the capital investment cost is high.

The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress the scattering range of the molten metal that has flowed out when a breakout occurs in a continuous casting operation of a molten metal such as molten steel. It is to provide a method for preventing the scattering of molten metal in a continuous casting machine, which can minimize damage to the continuous casting machine equipment and shorten the restoration work.

The gist of the present invention for solving the above problems is as follows.
[1] A method for preventing molten metal from scattering in a continuous casting machine in which a slab support roll is composed of a plurality of roll segments, and a breakout of the slab during casting is performed at a portion upstream of the roll segment in the casting direction. A method for preventing molten metal from scattering in a continuous casting machine, which comprises installing a nonflammable sheet for depositing molten metal that has flowed out of a solidified shell.
[2] The nonflammable sheet is configured so that after the molten metal deposited on the nonflammable sheet solidifies, the molten metal is removed from the roll segment together with the solidified metal. The method for preventing the scattering of molten metal in the continuous casting machine according to the above [1].

According to the present invention, since the nonflammable sheet is installed at the portion upstream of the casting direction of the roll segment, when the molten metal flows out from the solidified shell due to breakout, the molten metal that has flowed out is deposited on the nonflammable sheet. Therefore, the scattering range of the molten metal is narrowed, and the nonflammable sheet prevents welding of the roll segment and the molten metal, and the peelability of the bare metal after the molten metal is solidified is improved, resulting in recovery. The work can be shortened. In addition, only the non-combustible sheet is installed, the capital investment cost is minimized, a large amount of cooling water is not required, and the non-combustible sheet is installed at the position of the oxidation generated on the solidified shell surface. Since it is out of the range where the scale falls, regular cleaning is not required.

It is the schematic of an example of the slab continuous casting machine used when carrying out the method of preventing the scattering of molten metal which concerns on this invention. A schematic view of a support roll segment in which a nonflammable sheet for depositing molten steel spilled due to breakout is installed at a portion upstream of the support roll segment in the casting direction is shown. It is an external photograph of an aluminum heat-resistant sheet that can be used as a non-combustible sheet.

Hereinafter, the present invention will be described with reference to the accompanying drawings. In the present embodiment, a case where the molten metal is molten steel will be described.

FIG. 1 is a schematic view of an example of a slab continuous casting machine used when carrying out the method for preventing scattering of molten metal according to the present invention. In FIG. 1, reference numeral 1 is a vertical bending type slab continuous casting machine, 2 is a tundish, 3 is a sliding nozzle, 4 is a dipping nozzle, 5 is a mold for continuous casting, and 6 is a support roll among slab support rolls. , 7 is a guide roll (including a pinch roll) among the slab support rolls, 8 is molten steel, and 9 is a slab. The sliding nozzle 3 is a device that adjusts the flow rate of molten steel supplied from the tundish 2 to the mold 5.

In this slab continuous casting machine 1, all the slab support rolls are composed of roll segments, and all of the support rolls 6 installed directly under the mold 5 are installed in one support roll segment 10. .. The guide roll 7 installed on the downstream side in the casting direction from the support roll 6 includes a first guide roll segment 11, a second guide roll segment 12, a third guide roll segment 13, a fourth guide roll segment 14, and a fifth guide roll. It is installed in a plurality (8 pieces) of the segment 15, the sixth guide roll segment 16, the seventh guide roll segment 17, and the eighth guide roll segment 18.

The guide roll 7 includes a pinch roll that is rotated by the driving force of the electric motor and pulls out the slab 9 on the downstream side in the casting direction, but the pinch roll is not shown separately in FIG. The guide rolls other than the pinch rolls are not driven and rotate when they come into contact with the slab 9.

In this slab continuous casting machine 1, the molten steel 8 injected from the tundish 2 into the mold 5 via the immersion nozzle 4 is cooled by the mold 5 and a solidified shell (not shown) is formed on the contact surface with the mold 5. A slab 9 formed and having a solidified shell as a solidified shell and having unsolidified molten steel 8 inside is continuously supported below the mold 5 while being supported by a support roll 6 and a guide roll 7 provided below the mold 5. Is pulled out. A secondary cooling zone (not shown) in which a water spray nozzle or an air mist spray nozzle is arranged is formed in the gap between the slab support rolls adjacent to each other in the casting direction, and the slab 9 is a slab support roll. While passing through, it is water-cooled with the secondary cooling water of the secondary cooling zone to increase the thickness of the solidification shell and complete the solidification to the inside.

During continuous casting, mold powder (not shown) is added onto the molten steel surface of the mold 5. The mold powder flows into the gap between the inner wall surface of the mold 5 and the solidified shell, and is responsible for lubricating the mold 5 and the solidified shell. Therefore, since the mold powder flows into the gap between the inner wall surface of the mold 5 and the solidified shell and is consumed, the mold powder is continuously or intermittently on the molten steel surface of the mold 5 in order to make up for the consumed amount. Is added.

During this continuous casting, if the inflow of mold powder is insufficient due to factors such as changes in the composition of the mold powder, changes in melting characteristics due to it, or insufficient supply, lubrication by the mold powder is insufficient and solidification occurs. A so-called binding breakout may occur due to seizure of the shell and the mold 5.

In addition to breakout due to seizure due to poor inflow of mold powder, the high temperature of the molten steel 8 and foreign matter entering between the solidification shell and the mold 5 cause a delay in solidification of the solidification shell and locally solidify. A thin part of the shell is formed, and the thin part of the solidified shell breaks under the mold due to the static pressure of the unsolidified molten steel 8, and vertical cracks on the surface of the slab generated by the delay in solidification of the solidified shell open. In some cases, breakouts may occur.

The restrictive breakout occurs directly under the mold 5, but other breakouts may occur in the support roll segment 10 or in the first guide roll segment 11.

If a breakout occurs during the continuous casting operation, the sliding nozzle 3 is immediately closed and the supply of the molten steel 8 to the mold 5 is stopped, but on the upstream side in the casting direction from the position where the breakout occurs. All of the unsolidified molten steel 8 inside the slab 9 flows out from the broken portion of the solidified shell of the slab 9. For example, if a breakout occurs directly under the mold 5 during continuous casting of a slab slab having a thickness of 220 mm and a width of 2100 mm using a mold 5 having a length of 950 mm, about 2500 kg or more of molten steel 8 flows out. The outflowed molten steel 8 flows down toward the first guide roll segment 11 and the second guide roll segment 12 installed below the support roll segment 10 while adhering to the support roll 6 and the roll bearing of the support roll segment 10. To do.

The support roll 6, the guide roll 7, and the molten steel 8 adhering to these roll bearings are solidified, and the support roll 6 and the guide roll 7 become non-rotatable due to the bullion generated by the solidification of the molten steel 8. Therefore, the support roll 6 and the guide roll 7 to which the molten steel 8 has adhered and become non-rotatable cannot be used, and the roll segment having the support roll 6 and the guide roll 7 which has become non-rotatable is replaced.

As the scattering range of the outflowed molten steel 8 is narrowed, the number of roll segments to be replaced can be reduced. Therefore, in the present invention, the slab 9 being cast is located on the upstream side of the roll segment in the casting direction. A non-combustible sheet is installed to deposit the molten steel 8 that has flowed out of the solidified shell due to breakout. Since the molten steel 8 is deposited on the nonflammable sheet, the scattering range of the outflowed molten steel 8 is narrowed. Further, since the nonflammable sheet is interposed between the roll segment and the bare metal, welding of the roll segment and the molten steel 8 is prevented.

As the roll segment to which the nonflammable sheet is to be installed, the support roll segment 10 is indispensable, the first guide roll segment 11 is preferably installed, and the second guide roll segment 12 and the subsequent guide roll segments are also included. It is desirable to install a non-combustible sheet.

FIG. 2 shows a schematic view of the support roll segment 10 in which a nonflammable sheet for depositing the molten steel 8 that has flowed out due to breakout is installed at a portion of the support roll segment 10 on the upstream side in the casting direction. FIG. 2 is a schematic view of the support roll segment 10 viewed from the direction of the mold 5 toward the downstream side in the casting direction.

In FIG. 2, reference numeral 19 is a nonflammable sheet, 20 is a metal shatterproof steel plate, and 21 is a slab short side support roll that supports the short side surface of the slab 9. In FIG. 2, the slab 9 is drawn out in a direction perpendicular to the paper surface in a space surrounded by a pair of slab support rolls 6 facing each other and a pair of slab short side support rolls 21 facing each other.

As shown in FIG. 2, a bullion scattering prevention steel plate 20 covering the entire upper surface of the support roll segment 10 is installed at a portion upstream of the support roll segment 10 in the casting direction, and the bullion scattering prevention steel plate 20 is placed on the bullion scattering prevention steel plate 20. The nonflammable sheet 19 is detachably attached to the metal shatterproof steel plate 20 by using a wire or the like. The non-combustible sheet 19 is installed at least over the entire side of the metal shatterproof steel plate 20 facing the slab 9. Further, it is preferable to install it so as to cover at least 1/2 of the total area of the bullion scattering prevention steel plate 20, and preferably, it is installed so as to cover the entire surface of the bullion scattering prevention steel plate 20.

In FIG. 2, the non-combustible sheet 19 is not installed in the direction on the short side of the slab, but it is desirable to install the bullion scattering prevention steel plate 20 and the non-combustible sheet 19 in this area as well. As the nonflammable sheet 19, an aluminum heat-resistant sheet or the like may be used. FIG. 3 shows an external photograph of the aluminum heat-resistant sheet.

The aluminum heat-resistant sheet is made by attaching an aluminum sheet to linen cloth, has a fire resistance of "ISO 11612 certified A1 B1 C3 D3 E3", and has a sheet thickness of about 2 mm. Substances that can be used as nonflammable sheets other than aluminum heat-resistant sheets are felt cloth, aramid fiber heat-resistant felt, basalt fiber, silica cloth, ceramic fiber and the like.

Since the non-combustible sheet 19 is detachably installed on the bare metal scattering prevention steel plate 20, when a breakout occurs, the molten steel 8 is solidified after the molten steel 8 deposited on the non-combustible sheet 19 is solidified. It can be easily removed from the support roll segment 10 together with the solidified bare metal.

When the nonflammable sheet 19 is installed in the first guide roll segment 11 and subsequent guide roll segments, the nonflammable sheet 19 may be attached in the same manner as the method installed in the support roll segment 10.

As described above, according to the present invention, since the nonflammable sheet 19 is installed at a portion of the roll segment on the upstream side in the casting direction, when the molten metal flows out from the solidified shell due to breakout, the nonflammable sheet 19 Since the molten metal that has flowed out is deposited, the scattering range of the molten metal is narrowed, and the nonflammable sheet 19 prevents welding of the roll segment and the molten metal, and the bare metal is peeled off after the molten metal is solidified. Improve sex. As a result, the restoration work can be shortened. Further, only the non-combustible sheet 19 is installed, the capital investment cost is minimized, a large amount of cooling water is not required, and the non-combustible sheet 19 is installed on the surface of the solidified shell. Since it is out of the range where the oxide scale falls, regular cleaning is not required.

In the above embodiment, the case where the molten metal is molten steel has been described, but the molten metal is not limited to molten steel, and the present invention is carried out in accordance with the above even if molten aluminum, molten copper, hot metal, etc. are used. Can be done.

The present invention was carried out with a slab continuous casting machine of the same type as the vertical bending type slab continuous casting machine shown in FIG. The slab continuous casting machine is a facility capable of continuously casting slab slabs having a thickness of 220 mm and a width of 950 to 2200 mm at a slab drawing speed of 3.0 m / min, and as a roll segment, one support roll segment. And 14 guide roll segments, and the equipment length is 28m.

In the support roll segment, the first guide roll segment, and the second guide roll segment of this slab continuous casting machine, a metal scattering prevention steel plate is installed so as to cover the entire upper surface of each roll segment in the casting direction. Then, a nonflammable sheet was installed on the metal shatterproof steel plate. As the nonflammable sheet, an aluminum heat resistant sheet was used. The size of the aluminum heat-resistant sheet is 400 mm in width, 2000 mm in length, and 2 mm in thickness, and is on the side facing the slab of the metal shatterproof steel plate so as to cover a range of about 50% of the area of the bullion shatterproof steel plate. Installed in the area.

When the breakout occurred after the non-combustible sheet was installed, about 500 kg of bare metal was deposited on the non-combustible sheet.

We compared the breakout recovery work time after installing the non-combustible sheet with the breakout recovery work time before installing the non-combustible sheet. The average breakout recovery work time before installing the non-combustible sheet was 7.7 hours, but after installing the non-combustible sheet, the average breakout recovery work time was 7.2 hours. Therefore, it was confirmed that the restoration work time can be shortened by applying the present invention.

1 Slab continuous casting machine 2 Tandish 3 Sliding nozzle 4 Immersion nozzle 5 Mold 6 Support roll 7 Guide roll 8 Molten steel 9 Slab 10 Support roll segment 11 1st guide roll segment 12 2nd guide roll segment 13 3rd guide roll segment 14 4th guide roll segment 15 5th guide roll segment 16 6th guide roll segment 17 7th guide roll segment 18 8th guide roll segment 19 Non-combustible sheet 20 Bullion shatterproof steel plate 21 Cast piece short side support roll

Claims (2)

A method for preventing molten metal from scattering in a continuous casting machine in which a slab support roll is composed of a plurality of roll segments.
A metal shatterproof steel plate is installed on the upstream side of the roll segment in the casting direction so as to cover the entire upper surface of the roll segment in the casting direction (excluding the space where the slab is pulled out).
Any of aluminum heat-resistant sheet, felt cloth, aramid fiber heat-resistant felt, basalt fiber, silica cloth, and ceramic fiber as a non-combustible sheet for depositing molten metal that has flowed out of the solidified shell due to breakout of the slab during casting. Using silica
A method for preventing molten metal from scattering in a continuous casting machine, which comprises installing the nonflammable sheet on the bare metal scattering prevention steel plate before a continuous casting operation . The nonflammable sheet is characterized in that after the molten metal deposited on the nonflammable sheet solidifies, the molten metal is solidified and removed from the roll segment together with the generated metal. The method for preventing scattering of molten metal in the continuous casting machine according to claim 1.