JP7056400B2 - Manufacturing method for cooling rolls, double roll type continuous casting equipment, and thin-walled slabs - Google Patents

Description

The present invention supplies molten metal to a molten metal pool portion formed by a pair of cooling rolls and a pair of side dams, and forms and grows a solidified shell on the peripheral surface of the cooling rolls to produce thin-walled slabs. The present invention relates to a cooling roll used in a twin-roll type continuous casting apparatus, a twin-roll type continuous casting apparatus using this cooling roll, and a method for manufacturing a thin-walled slab.

As a method for producing thin-walled metal slabs, a molten metal pool portion formed by a pair of rotating cooling rolls and a pair of side dams, provided with a pair of cooling rolls having a water-cooled structure inside and rotating in opposite directions. A solidified shell is formed and grown on the peripheral surface of the cooling roll, and the solidified shells formed on the outer peripheral surfaces of the pair of cooling rolls are pressure-bonded at the roll kiss point to form a thin wall of a predetermined thickness. A twin-roll continuous casting apparatus for producing slabs is provided. Such a double roll type continuous casting device is applied to various metals.

In the above-mentioned twin roll type continuous casting apparatus, the molten metal is continuously supplied to the molten metal pool portion from the molten metal container arranged above the cooling roll via the immersion nozzle. The molten metal is discharged toward the peripheral surface of the cooling roll from the immersion nozzle arranged in the central portion of the molten metal pool portion, and flows to the pair of side weirs along the peripheral surface of the cooling roll. The molten metal solidifies and grows on the peripheral surface of the rotating cooling roll to form a solidified shell, and the solidified shell on the peripheral surface of each cooling roll is crimped at a kiss point.

The side weir, which is the side wall of the molten metal pool portion, slides on the side surface of the rotating cooling roll when casting a thin-walled slab to seal and hold the molten metal. Here, since the cooling roll needs to take a large amount of heat in an extremely short time when it comes into contact with the molten metal, the roll has an internal water-cooled structure. This cooling roll consists of a roll body and an outer peripheral sleeve attached to the outer peripheral portion thereof, and a copper alloy having high thermal conductivity is used as the material of the outer peripheral sleeve.
Here, the side weir is preheated before casting and is also heated from the outside during casting, but since it is always sliding with the cooling roll, it is removed from the cooling roll and cooled. When this cooling is excessive, the molten metal comes into contact with the cold side weir and solidifies on the side weir surface, and the generated solidified layer adheres to the side weir surface and grows. This is called bullion.

The bullion generated on the surface of the side weir in this way may grow into a thick wall and then be caught between the pair of cooling rolls together with the thin-walled slab cast on the peripheral surface of the cooling roll. ..
When the bullion is drawn between the pair of cooling rolls together with the thin-walled slab, the bullion is crimped between the cooling rolls together with the thin-walled slab, so that the thickness is locally increased. In addition, when the bullion is bitten into the pair of cooling rolls, the distance between the pair of cooling rolls temporarily increases, and the entire width of the thin-walled slab becomes thicker (solidification in the part without the bullion). It causes the occurrence of so-called hot band), which causes a delay and high temperature, and the accompanying fluctuation in the plate thickness of thin-walled slabs, quality defects such as surface defects, and operational troubles such as plate breakage and hot water leakage.

Further, in the above-mentioned twin-roll type continuous casting apparatus, when the pressure is reduced by a pair of cooling rolls, the tip of the solidification shell is broken to form floating crystals, and if these floating crystals are present in the molten steel metal pool portion, the hot water flows. Floating crystals stay in the vicinity of the side weir where stagnation is likely to occur, and eventually the fluidity is impaired and a slurry-like semi-solidified layer is formed. When the semi-solidified layer is also caught in a thin-walled slab, a hot band or the like is generated as in the case of the bare metal, and stable casting cannot be performed.

Therefore, in this twin-roll type continuous casting device, in order to uniformly promote solidification on the peripheral surface of the cooling roll to produce a sound thin plate, the generation and growth of the bullion and the semi-solidified layer on the surface of the side weir are required. Prevention is one of the most important issues in the process.
Therefore, for example, Patent Documents 1 and 2 propose a technique for suppressing the generation of bare metal on the surface of the side weir.

In Patent Document 1, by vibrating the side weir slidably contacted with the end surface of the cooling roll, the solidified shell (bullet) adhering to the inner surface of the side weir is quickly dropped off, and the entrainment in the thin-walled slab is suppressed. However, a bi-roll type continuous casting apparatus capable of stably producing a uniform thin-walled slab without causing breakage of the thin-walled slab has been proposed.
Patent Document 2 provides a vibration device that vibrates the side weir in the sliding contact surface with the end face of the cooling roll, vibrates the side weir during the unsteady state of casting, and vibrates the side weir during the steady state period. A method of stopping the vibration has been proposed.

Japanese Unexamined Patent Publication No. 60-184450 Japanese Unexamined Patent Publication No. 05-237603

By the way, in both Patent Documents 1 and 2, the vibration direction of the side weir is within the sliding surface of the end face of the side weir and the cooling roll, and the end face of the cooling roll and the side weir are always in contact with each other. Heat was unavoidable, the temperature of the side weir dropped, and the formation and growth of bare metal on the surface of the side weir could not be sufficiently suppressed.
Further, in Patent Document 1, the solidified shell (bullet) adhering to the inner surface of the side weir is configured to fall off at an early stage by vibrating the side weir, but simply vibrating the side weir is sufficient. The bullion and the semi-solidified layer could not be removed at an early stage, and there was a risk that the bullion and the semi-solidified layer would grow on the surface of the side weir.

The present invention has been made in view of the above-mentioned situation, and it is possible to suppress the generation of hot bands and the like due to the entrainment of a large-grown bullion and a semi-solidified layer, and it is possible to perform stable casting. It is an object of the present invention to provide a cooling roll, a twin-roll type continuous casting apparatus equipped with the cooling roll, and a method for manufacturing a thin-walled slab.

In order to solve the above problems, the cooling roll according to the present invention supplies molten metal to a molten metal pool portion formed by a pair of rotating cooling rolls and a pair of side dams, and supplies molten metal to the peripheral surface of the cooling roll. A cooling roll used in a twin-roll type continuous casting device that forms and grows a solidified shell to produce thin-walled slabs, and is provided with a recess at the boundary between the peripheral surface and the side surface of the widthwise end of the cooling roll. The recess has a length of 0.1 mm or more and 0.5 mm or less in the roll width direction, a length of 0.3 mm or more and 3 mm or less in the roll radial direction, and a circumferential length of 1 mm or more and 30 mm or less. The plurality of recesses are periodically arranged in the circumferential direction at the boundary portion, and the periodically arranged recesses are arranged at intervals of 30 mm or more and 250 mm or less in the circumferential direction. It is characterized by being done.

According to the cooling roll having this configuration, during casting, the molten metal is inserted into a recess provided at the boundary between the peripheral surface and the side surface of the widthwise end portion of the cooling roll and solidified, resulting in a burr-like solidified portion. It is formed. When this burr-like solidified portion slides with the side weir as the cooling roll rotates, it is integrated with the bullion and the semi-solidified layer on the surface of the side weir and is caught in the thin-walled slab. In this way, by entraining the bare metal or semi-solidified layer on the surface of the side weir in the thin-walled slab before it grows large, the generation of hot bands can be suppressed and stable casting can be performed. Will be.

Here, in the cooling roll of the present invention, the recess has a length of 0.1 mm or more and 0.5 mm or less in the roll width direction and a length of 0.3 mm or more and 3 mm or less in the roll radial direction. It is preferable that the circumferential length is within the range of 1 mm or more and 30 mm or less.
In this case, since the size of the recess is specified as described above, the molten metal can be accurately inserted into the recess, and the burr-like solidified portion allows the bare metal or semi-solidified layer on the surface of the side weir to be formed. It can be rolled into thin-walled slabs before they grow large. In addition, it is possible to prevent the quality of the end shape of the thin-walled slab from being significantly deteriorated.

Further, in the cooling roll of the present invention, it is preferable that a plurality of the recesses are periodically arranged in the circumferential direction at the boundary portion.
In this case, since a plurality of recesses provided at the boundary between the peripheral surface and the side surface of the widthwise end of the cooling roll are periodically arranged in the circumferential direction at the boundary, the bare metal on the surface of the side weir. And the semi-solidified layer can be accurately involved in the slab before it grows large.

Further, in the cooling roll of the present invention, it is preferable that the periodically arranged recesses are arranged at intervals of 30 mm or more and 250 mm or less in the circumferential direction.
In this case, the bare metal or the semi-solidified layer on the surface of the side weir can be accurately involved in the slab before it grows large.

Further, in the cooling roll of the present invention, the recess formed on one end side in the width direction of the cooling roll and the recess formed on the other end side in the width direction of the cooling roll are arranged at different positions in the circumferential direction. It is preferable that it is.
In this case, it is possible to prevent the bullion and the semi-solidified layer from being caught in both ends of the width of the thin-walled slab at the same position in the longitudinal direction of the thin-walled slab, and the slab can be rolled into the thin-walled slab by the involvement of the bullion and the semi-solidified layer. It is possible to suppress the influence and perform stable casting.

The twin-roll type continuous casting apparatus of the present invention supplies molten metal to a molten metal pool portion formed by a pair of rotating cooling rolls and a pair of side dams, and forms a solidified shell on the peripheral surface of the cooling rolls. It is a twin-roll type continuous casting apparatus that grows to produce thin-walled slabs, and is characterized by having the above-mentioned cooling roll.
According to the twin-roll type continuous casting apparatus having this configuration, since the above-mentioned cooling roll is provided, the metal and the semi-solidified layer on the surface of the side weir are hot by being caught in the thin-walled slab before it grows large. The generation of bands can be suppressed, and stable casting can be performed.

Here, in the dual roll type continuous casting apparatus of the present invention, one cooling roll and the other so that the recess formed in one cooling roll and the recess formed in the other cooling roll do not face each other at the roll kiss point. It is preferable that the cooling rolls of the above are arranged.
In this case, it is suppressed that the bare metal or semi-solidified layer caught in the solidified shell of one cooling roll and the bare metal or semi-solidified layer caught in the solidified shell of the other cooling roll face each other at the roll kiss point. Therefore, it is possible to suppress the influence on the thin-walled slab due to the entrainment of the bare metal and the semi-solidified layer, and to perform stable casting.

In the method for casting a thin-walled slab of the present invention, molten metal is supplied to a molten metal pool portion formed by a pair of rotating cooling rolls and a pair of side dams, and a solidified shell is formed on the peripheral surface of the cooling rolls. It is a method for casting a thin-walled slab that is grown to produce a thin-walled slab, and is characterized by using the above-mentioned cooling roll.
According to the method of casting a thin-walled slab having this configuration, since the above-mentioned cooling roll is used, the bullion and the semi-solidified layer on the surface of the side weir can be involved in the slab before it grows large, and it is hot. The generation of bands can be suppressed, and stable casting can be performed.

Here, in the method for casting a thin-walled slab of the present invention, when the contact length L between the molten metal and the cooling roll in the circumferential direction in the molten metal pool portion is set, the plurality of the above are periodically arranged. It is preferable that the distance between the recesses is L or less.
In this case, it is possible to accurately entrain the bare metal or the semi-solidified layer on the surface of the side weir into the slab before it grows large enough to reach the surface of the molten metal from the roll kiss point.

As described above, according to the present invention, a cooling roll capable of suppressing the generation of hot bands and the like due to entrainment of a large-grown bullion and a semi-solidified layer, and capable of stable casting, this cooling. It is possible to provide a twin-roll type continuous casting apparatus equipped with a roll and a method for manufacturing a thin-walled slab.

It is explanatory drawing which shows an example of the twin-roll type continuous casting apparatus which is an embodiment of this invention. It is a partially enlarged explanatory view of the twin-roll type continuous casting apparatus shown in FIG. It is explanatory drawing which shows the flow | flow of the molten metal part of the molten steel pool part in the twin-roll type continuous casting apparatus shown in FIG. It is explanatory drawing which shows the generation area of the bullion in the side weir in the twin-roll type continuous casting apparatus shown in FIG. It is explanatory drawing of the cooling roll which is an embodiment of this invention. (A) is a side view, (b) is one end view, and (c) is the other end view. It is a partially enlarged explanatory view of the cooling roll shown in FIG. FIG. 5 is a cross-sectional explanatory view of a recess of the cooling roll shown in FIG. It is explanatory drawing which shows the arrangement of a pair of cooling rolls in the twin-roll type continuous casting apparatus shown in FIG. It is a graph which shows the surface temperature measurement result of the slab in Example 1 of this invention. It is a graph which shows the surface temperature measurement result of the slab in the comparative example. It is a schematic explanatory drawing of the thin-walled slab obtained by Example 1 of this invention. It is a schematic explanatory drawing of the thin-walled slab obtained by the comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, the metal to be cast will be described as steel. The present invention is not limited to the following embodiments.

In the present embodiment, molten steel is used as the molten metal, and the thin-walled slab 1 made of a steel material is manufactured. The steel types include, for example, 0.001 to 0.01% C ultra-low coal steel, 0.02 to 0.05% C low coal steel, 0.06 to 0.4% C medium coal steel, 0.5. ~ 1.2% C high coal steel, austenite stainless steel represented by SUS304 steel, ferrite stainless steel represented by SUS430 steel, 3.0 ~ 4.0% Si directional electromagnetic steel, 0.1 ~ Examples thereof include 6.5% Si non-directional electromagnetic steel (% is mass%).
Further, in the present embodiment, the width of the thin-walled slab 1 to be manufactured is within the range of 200 mm or more and 1800 mm or less, and the thickness is within the range of 0.8 mm or more and 5 mm or less.

Next, the twin-roll type continuous casting apparatus 10 according to the present embodiment will be described.
The twin-roll continuous casting apparatus 10 shown in FIG. 1 includes a pair of cooling rolls 20 (20A, 20B), pinch rolls 12, 12 and 13, 13 for supporting the thin-walled slab 1, and a pair of cooling rolls 20 (20A). , 20B), the side weir 15 disposed at the widthwise end, and the molten steel 3 supplied to the molten steel pool portion 16 defined by the pair of cooling rolls 20 (20A, 20B) and the side weir 15. It includes a tundish 18 for holding and a dipping nozzle 19 for supplying the molten steel 3 from the tundish 18 to the molten steel pool portion 16.

Here, as shown in FIG. 2, the molten steel pool portion 16 is defined by disposing the side weir 15 on the end surface of the cooling roll 20.
As shown in FIG. 3, the molten metal surface of the molten steel pool portion 16 has a rectangular shape surrounded on all sides by the peripheral surface of the pair of cooling rolls 20 (20A, 20B) and the pair of side weirs 15, 15. The immersion nozzle 19 is arranged at the center of the rectangular surface of the hot water.
Further, as shown in FIG. 4, the sliding portion of the side weir 15 with the molten steel 3 in the molten steel pool portion 16 has a substantially inverted triangular shape.

As shown in FIG. 3, the flow of the molten steel 3 in the molten steel pool portion 16 flows from the immersion nozzle 19 toward the peripheral surface of the cooling roll 20, and is along the peripheral surface of the cooling roll 20 on the side of the pair of side weirs 15. It flows to each. The contact point between the cooling roll 20 and the side weir 15 is a dead zone for the flow of the molten steel 3, and is a region (stagnation region) D in which the molten steel 3 does not flow sufficiently and stagnates.

As shown in FIG. 5, in the cooling roll 20, recesses 21 recessed in the roll radial direction and the roll width direction are provided at the boundary portion between the peripheral surface and the side surface of the width direction end portion thereof.
In the present embodiment, as shown in FIG. 5, it is preferable that a plurality of recesses 21 are periodically arranged in the circumferential direction at the boundary between the peripheral surface and the side surface of the widthwise end portion of the cooling roll 20.

As shown in FIGS. 6 and 7, the recess 21 has a length a in the roll width direction of 0.1 mm or more and 0.5 mm or less, and a length b in the roll radial direction of 0.3 mm or more and 3 mm or less. It is preferable that the length c in the circumferential direction is within the range of 1 mm or more and 30 mm or less.
Further, it is preferable that the circumferential distance p (distance between the center positions of the recesses 21 as shown in FIG. 6) of the periodically arranged recesses 21 is within the range of 30 mm or more and 250 mm or less.
In this embodiment, when the contact length L between the molten steel 3 and the cooling roll 20 in the molten steel pool portion 16 is set in the circumferential direction, the distance between the plurality of periodically arranged recesses 21 in the circumferential direction is L or less. It is preferable that it is.

Further, in the present embodiment, the recesses 21 are arranged so as to divide one circumference (360 °) proportionally at equal intervals, and are arranged at intervals of 8 ° or more and 40 ° or less in terms of central angle. Is preferable.

Further, in the cooling roll 20 of the present embodiment, as shown in FIG. 5, a recess 21 formed on one end side in the width direction (left side in FIG. 5) of the cooling roll 20 and the other end side in the width direction of the cooling roll 20. It is preferable that the recesses 21 formed in (the right side in FIG. 5) are arranged at different positions in the circumferential direction. That is, as shown in FIGS. 5 (b) and 5 (c), the recess 21 formed on the other end surface is arranged between the recesses 21 formed on one end surface in the width direction of the cooling roll 20. Is preferable.

Further, in the double roll type continuous casting apparatus 10 of the present embodiment, as shown in FIG. 8, the recess 21 formed in one cooling roll 20A and the recess 21 formed in the other cooling roll 20B are formed. It is preferable that one cooling roll 20A and the other cooling roll 20B are arranged so as not to face each other at the roll kiss point.

Further, in the double roll type continuous casting apparatus 10 of the present embodiment, the recess 21 formed on one end side in the width direction of one cooling roll 20A and the recess formed on the other end side in the width direction of one cooling roll 20A. 21 and the recess 21 formed on one end side in the width direction of the other cooling roll 20B and the recess 21 formed on the other end side in the width direction of the other cooling roll 20B are arranged so as not to coincide with each other at the roll kiss point. Is preferable.

In the twin roll type continuous casting apparatus 10, the molten steel 3 is supplied from the tundish 18 to the molten steel pool portion 16 via the dipping nozzle 19. In the molten steel pool portion 16, the solidified shells 5 and 5 grow on the peripheral surface of the cooling roll 20 by contacting and cooling the molten steel 3 in contact with the rotating cooling rolls 20 (20A, 20B). Then, the solidified shells 5, 5 formed on the pair of cooling rolls 20 (20A, 20B) are pressure-bonded to each other at the roll kiss point, whereby the thin-walled slab 1 having a predetermined thickness is cast.

At this time, since the side weir 15 is always sliding with the cooling roll 20, heat is removed from the cooling roll 20 and cooled. Therefore, as shown in FIG. 4, the bullion grows and accumulates in the region S near the sliding line with the cooling roll 20 on the surface of the side weir 15.
Further, as shown in FIG. 3, the contact point between the cooling roll 20 and the side weir 15 is a dead zone for the flow of the molten steel 3, and the region where the molten steel 3 does not flow sufficiently and stagnates (stagnation area). It becomes D. Therefore, the suspended crystals existing in the molten steel pool portion 16 stay in the stagnant region D to form a semi-solidified layer. If the bare metal or the semi-solidified layer is caught in the thin-walled slab 1 in a state of being greatly grown, a hot band or the like is generated and stable casting cannot be performed.

Therefore, in the present embodiment, as described above, by providing the recess 21 at the boundary between the peripheral surface and the side surface of the widthwise end portion of the cooling roll 20, the molten steel 3 is inserted into the recess 21 and solidified. The formed burr-like solidified portion is integrated with the bare metal and the semi-solidified layer formed on the surface of the side weir 15, and these bare metal and the semi-solidified layer are involved in the thin-walled slab 1 before they grow large. It is configured as follows.

Here, as described above, the reason for defining the size and arrangement of the recess 21 in the cooling roll 20 will be described.

By setting the length a of the recess 21 in the roll width direction to 0.1 mm or more, the molten steel 3 can be reliably inserted into the recess 21 against the surface tension of the molten steel 3. Further, by setting the length a of the recess 21 in the roll width direction to 0.5 mm or less, it is possible to prevent the shape of the end portion of the thin-walled slab 1 from being disturbed.
From the above, in the present embodiment, it is preferable that the length a of the recess 21 in the roll width direction is within the range of 0.1 mm or more and 0.5 mm or less.

By setting the length b of the recess 21 in the roll radial direction to 0.3 mm or more, the molten steel 3 can be reliably inserted into the recess 21 against the surface tension of the molten steel 3. Further, by setting the length b of the recess 21 in the roll radial direction to 3 mm or less, it is possible to prevent the shape of the end portion of the thin-walled slab 1 from being disturbed.
From the above, in the present embodiment, it is preferable that the length b of the recess 21 in the roll radial direction is within the range of 0.3 mm or more and 3 mm or less.

By setting the circumferential length c of the recess 21 to 1 mm or more, the molten steel 3 can be reliably inserted into the recess 21 against the surface tension of the molten steel 3. Further, by setting the circumferential length c of the recess 21 to 30 mm or less, it is possible to prevent the shape of the end portion of the thin-walled slab 1 from being disturbed.
From the above, in the present embodiment, it is preferable that the circumferential length c of the recess 21 is within the range of 1 mm or more and 30 mm or less.

By setting the circumferential interval p of the periodically arranged recesses 21 to 30 mm or more, the bare metal and the semi-solidified layer existing between the adjacent recesses 21 grow to some extent and are inserted into the recesses 21 to solidify. The formed burr-like solidified portion can be accurately involved in the thin-walled slab 1. Further, by setting the circumferential interval p of the recesses 21 to 250 mm or less, it is possible to suppress the formation of a coarse bullion and a semi-solidified layer.
From the above, in the present embodiment, it is preferable that the circumferential distance p of the periodically arranged recesses 21 is within the range of 30 mm or more and 250 mm or less.

Further, when the contact length L in the circumferential direction between the molten steel 3 and the cooling roll 20 in the molten steel pool portion 16 is set, the circumferential distance p of the plurality of periodically arranged recesses 21 is set to L or less. It is preferable because it can suppress the formation of a coarse metal and a semi-solidified layer that reaches from the roll kiss point to the surface of the molten metal.
The circumferential spacing p of the recesses 21 is more preferably L × (1/4) or more and L × (1/2) or less.

According to the present embodiment having the above configuration, since the recess 21 is provided at the boundary between the peripheral surface and the side surface of the widthwise end portion of the cooling roll 20, the molten steel 3 is formed in the recess 21 during casting. It is inserted and solidified to form a burr-like solidified portion, and when this burr-like solidified portion slides with the side dam 15 as the cooling roll 20 rotates, the bare metal or semi-solidified layer on the surface of the side dam 15 It will be integrated with the thin-walled slab 1 and the bare metal and the semi-solidified layer can be entangled with the thin-walled slab 1 before it grows large, and it is possible to suppress the generation of hot bands. Become.

Further, it is preferable that the recess 21 formed on one end side in the width direction of the cooling roll 20 and the recess 21 formed on the other end side in the width direction of the cooling roll 20 are arranged at different positions in the circumferential direction. .. In this case, it is possible to prevent the bullion and the semi-solidified layer from being caught in both ends of the width of the thin-walled slab 1 at the same position in the longitudinal direction of the thin-walled slab 1, and the thin-walled slab due to the entanglement of the bullion and the semi-solidified layer. It is possible to suppress the influence on 1 and perform stable casting.

Further, in the present embodiment, one cooling roll 20A and the other cooling roll 20A are cooled so that the recess 21 formed in one cooling roll 20A and the recess 21 formed in the other cooling roll 20B do not face each other at the roll kiss point. It is preferable that the roll 20B and the roll 20B are arranged. In this case, the bare metal or semi-solidified layer caught in the solidified shell 5 of one cooling roll 20A and the bare metal or semi-solidified layer caught in the solidified shell 5 of the other cooling roll 20B come into contact with each other at the roll kiss point. This can be suppressed, the influence on the thin-walled slab 1 due to the entrainment of the bare metal and the semi-solidified layer can be suppressed, and stable casting can be performed.

Although the cooling roll, the double-roll type continuous casting apparatus, and the method for manufacturing the thin-walled slab, which are the embodiments of the present invention, have been specifically described above, the present invention is not limited to this, and the technical aspects of the present invention are not limited thereto. It can be changed as appropriate without departing from the idea.
For example, in the present embodiment, as shown in FIG. 1, a twin-roll type continuous casting apparatus in which pinch rolls are arranged has been described as an example, but the arrangement of these rolls and the like is not limited, and the design is appropriately changed. You may.
Further, the shape of the recess 21 is not limited to that illustrated in the figure. Further, the arrangement of the recesses 21 and the like is not limited to this embodiment.

The results of experiments carried out in order to confirm the effects of the present invention will be described below.

Using the twin roll type continuous casting apparatus having the configuration shown in FIG. 1, 0.05% C, 0.6% Si, 1.5% Mn, 0.03% Al, the balance Fe and impurities were obtained in% by mass. A thin-walled slab made of steel having a different composition was cast. The liquidus temperature of the steel having this composition was 1517 ° C., and the molten steel temperature to be injected into the molten steel pool portion so as to have a superheat degree of 30 to 50 ° C. was 1547 to 1567 ° C.

Here, the cooling roll has a diameter of 600 mm and a width of 800 mm, and is composed of an internal water-cooled roll body and a copper sleeve attached to the outer peripheral portion thereof. bottom. Then, as shown in Table 1, a recess is provided at the boundary between the peripheral surface and the side surface of the widthwise end of the cooling roll.
Then, a thin-walled slab having a thickness of 2 mm was cast at a molten steel depth of 212 mm and a peripheral speed of the cooling roll of 50 m / min in the molten steel pool portion.

The surface temperature of the thin-walled slab directly under the cooling roll is measured with a radiation thermometer, and it is judged that a hot band has occurred when a peak that is 30 ° C or higher from the steady temperature occurs, and the number of times the hot band is generated is determined. Counted. The evaluation results are shown in Table 1.
Further, the temperature measurement result of Example 1 of the present invention is shown in FIG. 9, and the temperature measurement result of the comparative example is shown in FIG. Further, FIG. 11 shows the state of entrainment of the bare metal in the thin-walled slab of Example 1 of the present invention, and FIG. 12 shows the state of entrainment of the bare metal in the thin-walled slab of the comparative example.

In the comparative example in which the cooling roll was not provided with a recess, a large amount of hot bands were generated because the large-grown bullion was irregularly involved.
On the other hand, in the example of the present invention in which the cooling roll is provided with the recess, the number of times of hot band generation is greatly reduced.
In particular, in Examples 1 to 4 of the present invention in which the size of the recesses and the spacing in the circumferential direction are within a desirable range, there is no hot band.

From the above results, it was confirmed that according to the present invention, it is possible to suppress the frequent generation of hot bands and the like due to the large growth of the bare metal and the semi-solidified layer being caught in the slab, and the casting can be performed stably.

1 Thin-walled slab 3 Molten steel (molten metal)
5 Solidification shell 10 Double roll type continuous casting equipment 15 Side weir 16 Molten steel pool part (molten metal pool part)
20 Cooling roll 21 Recess

Claims (6)

A twin roll that supplies molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side dams, and forms and grows a solidified shell on the peripheral surface of the cooling roll to produce thin-walled slabs. A cooling roll used in a continuous casting machine.
A recess is provided at the boundary between the peripheral surface and the side surface of the widthwise end of the cooling roll.
The recess has a length of 0.1 mm or more and 0.5 mm or less in the roll width direction, a length of 0.3 mm or more and 3 mm or less in the roll radial direction, and a circumferential length of 1 mm or more and 30 mm or less. It is said to be within the range,
A plurality of the recesses are periodically arranged in the circumferential direction at the boundary portion, and the periodically arranged recesses are arranged at intervals of 30 mm or more and 250 mm or less in the circumferential direction. Cooling roll. The claim is characterized in that the recess formed on one end side in the width direction of the cooling roll and the recess formed on the other end side in the width direction of the cooling roll are arranged at different positions in the circumferential direction. The cooling roll according to 1 . A twin roll that supplies molten metal to a molten metal pool portion formed by a pair of rotating cooling rolls and a pair of side dams, and forms and grows a solidified shell on the peripheral surface of the cooling roll to produce thin-walled slabs. It is a type continuous casting device,
A twin-roll continuous casting apparatus comprising the cooling roll according to claim 1 or 2 . A claim is characterized in that one cooling roll and the other cooling roll are arranged so that the recess formed in one cooling roll and the recess formed in the other cooling roll do not face each other at the roll kiss point. 2. The twin-roll type continuous casting apparatus according to 3. A thin-walled casting that supplies molten metal to a molten metal pool portion formed by a pair of rotating cooling rolls and a pair of side dams, and forms and grows a solidified shell on the peripheral surface of the cooling rolls to produce thin-walled slabs. It ’s a piece casting method.
A method for casting a thin-walled slab, which comprises using the cooling roll according to claim 1 or 2 . When the contact length between the molten metal and the cooling roll in the circumferential direction is L in the molten metal pool portion, the distance between the plurality of periodically arranged recesses in the circumferential direction is L or less. The method for casting a thin-walled slab according to claim 5 .

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