TWI696506B - Manufacturing method of cast strip - Google Patents

Abstract

The present invention provides a method for manufacturing a cast strip by supplying a molten metal into a molten metal pool section formed by a pair of cooling drums and a pair of side weirs, and generating and growing solidified shells on circumferential surfaces of the pair of the cooling drums.

In a first step, both ends of the cooling drum in the rotational axis direction are respectively pressed with a first pressure.

In a second step, until the cooling drum rotates at least one time after the first step, the both ends of the cooling drum are respectively pressed with a second pressure, which is higher than the first pressure.

In a third step, a pressure control is performed such that the sum of the counter forces from the both ends of the cooling drum becomes a predetermined value and that the rotational axes of the pair of the rotational drums are maintained in parallel.

Description

Casting manufacturing method

Field of invention

The present invention relates to a method for manufacturing a slab by supplying molten metal to a molten metal reservoir formed by a pair of cooling drums and a pair of side weirs to produce a slab.

Background of the invention

As a method of manufacturing a thin-walled cast metal sheet (hereinafter sometimes referred to as a cast strip), for example, as shown in Patent Documents 1 and 2, a double-roll continuous casting using a cooling drum having a water-cooled structure inside The manufacturing method of the device. In such a manufacturing method, molten metal is supplied to a molten metal reservoir formed between a pair of rotating cooling drums, and solidified shell layers formed and grown on the peripheral surface of the pair of cooling drums are at the point of contact of the drums The bonding is performed and rolled to produce a predetermined thickness of the cast piece. The manufacturing method using such a double drum type continuous casting device can be applied to various metals.

Here, in the above-described twin-roller continuous casting apparatus, in order to produce a slab with a uniform thickness in the sheet width direction, the pressure is controlled so that the rotation axes of the pair of cooling rollers are kept parallel.

Therefore, Patent Document 1 proposes a method of detecting and adding the pressing force at both ends of one side of the cooling drum, and using the signal based on this, the other side of the cooling drum is caused by the hydraulic cylinder The two ends of are moved in parallel so that the sum of the pressing forces at both ends of the cooling drum on one side becomes a predetermined value.

When casting is started in the above-mentioned double-drum continuous casting apparatus, a dummy sheet is sandwiched between cooling drums, and molten metal is supplied to a pair of cooling drums and a pair of side weirs. The formed molten metal reservoir. Next, at a stage where a certain amount of molten metal is accumulated in the molten metal storage part, the cooling drum is rotated, and the cast piece is formed to be connected to the dummy sheet, and the dummy sheet is pulled out from between the cooling drums and connected to the dummy sheet Cast piece.

Therefore, when the casting is not stable at the beginning, there may be a case where the deviation of the thickness of the solidified shell becomes large, and under the pressure control as in Patent Document 1, the roll contact point cannot be sufficiently rolled and solidified Shell. In this case, an unsolidified portion is formed at the center of the thickness of the slab, and the surface temperature of the slab becomes relatively high, resulting in insufficient strength, fracture of the slab, etc., and the casting cannot be started stably. In particular, by growing the solidified shell in a state where the cooling drum has been stopped, it becomes a wall thick portion (locally thickened portion) formed on the cast piece at the beginning of casting (locally thickened portion, hereinafter sometimes referred to as In the case of a wall thickness part), when this wall thickness part passes through the roller contact point, the casting becomes unstable.

Therefore, in Patent Document 2, it has been proposed to switch the pressure control between a pair of cooling drums at the beginning of casting and at a steady state Methods.

Specifically, in the first step after the cooling drum is rotated and started until the wall thickness portion of the slab passes through the closest point (drum contact point) of the cooling drum, the parallel control of the cooling drum is not performed, but a pair of The cooling drum is pressed with a relatively low pressure in the direction approaching. In addition, in the second step from the first step to the time when the influence of the shell flushing by the discharge flow of molten steel from the nozzle disappears, the parallel control of the cooling drum is not performed, but it is more than the first step. High pressure to press. In the third step after the second step, parallel control is performed so that the rotation axes of the pair of cooling drums are parallel to each other.

In this Patent Document 2, when the thickness variation of the solidified shell layer becomes unstable at the beginning of casting, the pair of cooling rollers is simply pressed, so the solidified shell layers can be rolled sufficiently at the contact point of the rollers Shrinkage, and it can suppress the formation of unsolidified parts in the central part of the thickness of the cast piece. In addition, the second step until the influence of the shell flushing by the discharge flow of molten steel from the nozzle disappears is until the molten metal surface of the molten metal rises sufficiently. During this period, the cooling drum Rotate about 0.4 times.

Prior technical literature Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 01-166863

Patent Document 2: Japanese Patent No. 2957040

Summary of the invention

However, even when the pressure control of the pair of cooling drums is performed according to the method described in Patent Document 2, there may be a case where the raw metal formed on the surface of the side weir is bitten into when the casting starts Between the cooling rollers, it becomes impossible to sufficiently roll the solidified shell layers at the roller contact points, resulting in fracture of the slab.

The present invention has been made in view of the foregoing circumstances, and an object of the present invention is to provide a method of manufacturing a slab that can suppress the breakage of a slab in a twin-roll continuous casting device and can start casting stably.

The gist of the present invention is as follows.

(1) The first aspect of the present invention is a casting method of slabs, which supplies molten metal to a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs, and A solidified shell is formed and grown on the peripheral surface of the cooling drum to produce a slab. The casting method of the slab is: in the first step, one end side and the other end side of the pair of cooling drums in the rotation axis direction Pressing each other with the same first pressure toward the pair of cooling rollers toward each other, wherein the first step is to allow the molten metal to be supplied to the molten metal in a state where the pair of cooling rollers have been stopped when casting starts The wall thickness portion of the slab formed when the metal accumulates, after the rotation of the cooling drum is activated to pass through the pair of The step up to the closest point of the cooling drum, in the second step until the pair of cooling drums rotates more than one revolution after the first step, is to one end side and the other end of the pair of cooling drums in the rotation axis direction The sides are pressed at a second pressure that is the same and higher than the first pressure, toward the pair of cooling rollers toward each other. In the third step after the second step, pressure control is performed so that the first The total value of the reaction force on one end side and the other end side of the rotation axis direction of the cooling drum becomes a predetermined value, and the mutual rotation axes of the pair of cooling drums are kept parallel.

(2) In the method of manufacturing a slab described in (1) above, the second step may be a period from after the first step to when the pair of cooling drums rotates two or more times.

According to the method of manufacturing slabs described in (1) and (2) above, during the period when the thermal expansion portion of the cooling drum formed at the start of casting is in contact with the side weir, the parallel The one end side and the other end side of the cooling drum in the rotation axis direction are pressed against each other with the same pressure. Therefore, even if the raw metal bites between the cooling drums, the solidified shell layers can be sufficiently shrunk to each other at the drum contact point, and the formation of an unsolidified portion in the central portion of the thickness of the slab can be suppressed. With this, it is possible to suppress the fracture of the cast piece and start casting stably.

Furthermore, in the first step, since one end side and the other end side of the pair of cooling drums in the rotation axis direction are pressed toward the pair of cooling drums toward each other with the same first pressure, the wall thickness portion can be made Stable Through the cooling roller room.

In addition, in the second step, since the cooling drum is pressed at a second pressure higher than the first pressure, the solidified shell layers can be sufficiently shrunk at the contact point of the drum, and the thickness of the slab can be suppressed The unsolidified part is formed in the central part.

In particular, according to the method of manufacturing slabs described in (2) above, by setting the period until the cooling drum rotates two or more times as the second step, it is formed so as to remain even up to the second circle In the case of the aforementioned thermal expansion portion, the one end side and the other end side of the pair of cooling drums in the rotation axis direction are still pressed with the same pressure. Therefore, it is possible to sufficiently roll the solidified shell layers at the roller contact point, and it is possible to suppress the formation of an unsolidified portion at the center of the thickness of the slab. Thereby, the fracture of the cast piece can be suppressed, and casting can be started stably.

In this way, according to the present invention, it becomes possible to provide a method of manufacturing a cast piece that can suppress the breakage of a cast piece and can start casting stably in a twin-roller continuous casting device.

1: casting

3: molten steel (molten metal)

5: solidified shell

10: Double drum continuous casting device

11, 11a, 11b: cooling roller

13: pinch roller

15: Side Weir

15a: substrate

15b: Ceramic plate

16: Molten steel tank part (Molten metal storage part)

18: feeding trough

19: Dipping nozzle

21A, 21B: hydraulic cylinder

22A, 22B: Dynamometer

24: Reaction Force Control Department

E: Thermal expansion

M: raw metal

P: closest point

R: direction of drum rotation

DS: drive side

WS: Working side

FIG. 1 is an explanatory diagram showing an example of a twin-roller continuous casting apparatus used in a method of manufacturing slabs according to an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a part of the double-drum continuous casting apparatus shown in FIG. 1.

Fig. 3 is an enlarged explanatory view of a side weir of the double-drum continuous casting apparatus shown in Fig. 1.

Fig. 4 is an explanatory cross-sectional view of Fig. 3.

5 is an explanatory diagram of a cooling drum and side weirs at the start of casting.

6 is an explanatory diagram showing the pressure control method of the cooling drum in the first step, the second step, and the third step.

7 is a graph showing the relationship between the roller reaction force and the roller gap in the comparative example.

8 is a graph showing the relationship between the roller reaction force and the roller gap in Example 1 of the present invention.

Forms for carrying out the invention

In order to solve the above-mentioned problems, the inventors of this case devoted themselves to the results of the review and obtained the following knowledge and insights.

In the double-roller continuous casting apparatus, as described above, the molten metal is supplied to the molten metal reservoir with the cooling drum stopped, so that it can contact the molten metal at the closest point (roller contact point) of the cooling drum The contact time becomes longer, and is locally heated to thermally expand, and a thermal expansion portion is formed. On the other hand, because the molten metal is not in contact with the molten metal in front of the drum contact point in the rotation direction of the drum, there is no thermal expansion, but a large difference in height from the thermal expansion portion is generated.

In addition, when the cooling drum rotates and the above-mentioned thermal expansion portion comes into contact with the side weir, a gap is formed between the side weir and the cooling drum. In this gap, the molten metal can be run in. The molten metal that runs in is solidified and integrated with the raw metal on the surface of the side weir, and bites it between the cooling rollers. At this time, in the case of parallel control of the cooling drum, it will There is a concern that there is a region where the solidified shell layers cannot be sufficiently rolled at the roller contact point, and an unsolidified portion is formed at the center of the thickness of the slab and the slab is broken.

Furthermore, as time passes, local thermal expansion is suppressed, and the effect of the thermal expansion part described above disappears.

Hereinafter, a method for manufacturing a cast piece according to an embodiment of the present invention created based on the above knowledge will be described with reference to the attached drawings. In addition, this invention is not limited to the invention of the following embodiment.

Here, in this embodiment, the molten steel is used as the molten metal, and the cast piece 1 made of the steel material is manufactured. In addition, in the present embodiment, it is assumed that the width of the manufactured slab 1 is in the range of 200 mm or more and 1800 mm or less, and the thickness is in the range of 0.8 mm or more and 5 mm or less.

First, the twin-roller continuous casting apparatus 10 used in the method of manufacturing a slab according to this embodiment will be described.

The double-drum type continuous casting device 10 shown in FIG. 1 includes: a pair of cooling drums 11 and 11; pinch rolls 13 and 13 to support the slab 1; a pair of side weirs 15 and 15 arranged on a pair of cooling drums 11. Both ends in the width direction of the 11; feed trough 18 to hold the molten steel 3, and the aforementioned molten steel 3 is supplied to the molten steel divided by these pair of cooling drums 11, 11 and a pair of side weirs 15, 15 The tank portion 16; and the immersion nozzle 19, which supplies the molten steel 3 from the feed tank 18 to the molten steel tank portion 16.

In this double-drum continuous casting apparatus 10, the molten steel 3 is cooled by contacting the rotating cooling drums 11, 11 to grow solidified shell layers 5, 5 on the peripheral surfaces of the cooling drums 11, 11. In addition, by forming the solidified shells 5 and 5 formed on the pair of cooling rollers 11 and 11 The contact points are crimped to cast a slab 1 of a predetermined thickness.

Here, as shown in FIG. 2, by disposing the side weir 15 on the end surface of the cooling drum 11, it can be divided into molten steel groove portions 16.

As shown in FIG. 2, the molten steel surface of the molten steel groove portion 16 is formed into a rectangular shape surrounded by a pair of peripheral surfaces of the cooling drums 11 and 11 and a pair of side weirs 15 and 15. A dipping nozzle 19 is arranged at the center of the melt surface.

In addition, as shown in FIG. 3, the contact portion of the side weir 15 with the molten steel 3 is formed substantially in an inverted triangle shape. At the start of casting, since the temperature of the side weir 15 is relatively low, the raw metal M is generated at the contact portion.

In addition, the side weir 15 includes, as shown in FIG. 4, a substrate 15a and a ceramic plate 15b disposed in an area that is in sliding contact with the cooling drum 11. The ceramic plate 15b is a harder refractory than the substrate 15a Posed. 4 is a horizontal cross section of the contact portion (point E of FIG. 5(d)) of the end surface of the cooling drum 11 and the ceramic plate 15b.

Here, at the start of casting of the twin-roller continuous casting apparatus 10, a dummy sheet (not shown) is inserted between the cooling drums 11 and 11 with the pair of cooling drums 11 and 11 stopped and oriented The molten steel groove portion 16 supplies molten steel 3.

Then, the cooling drums 11 and 11 are rotated and the slab 1 is pulled out by the lower side of the cooling drums 11 and 11.

At this time, at the beginning of casting, the molten steel 3 of the molten steel groove portion 16 is solidified and the thickness of the slab 1 becomes thicker, forming a nodular wall thickness portion, that is, forming the thickness of the slab 1 partially The enlarged area.

In addition, in the molten steel tank portion 16, the shell flushing of the solidified shell layer 5 by the discharge flow of the molten steel 3 from the immersion nozzle 19 occurs. This rinsing of the shell layer does not occur when the height of the melt surface of the molten steel groove portion 16 becomes high.

Here, the relationship between the cooling drum 11 and the side weir 15 at the beginning of casting will be described using FIG. 5.

First, as shown in FIG. 5( a ), before the molten steel 3 is supplied, the cooling drum 11 and the side weir 15 are in close contact with each other.

Then, the molten steel 3 is supplied with the cooling drums 11 and 11 stopped. In this way, as shown in FIG. 5( b ), in the vicinity of the closest point P (roller contact point) of the cooling drums 11 and 11, the cooling drum 11 thermally expands by contact with the molten steel 3 and forms a thermal expansion portion E. Furthermore, since the area in the front of the rotation direction R of the drum in the direction of the closest point P of the cooling drums 11 and 11 is not in contact with the molten steel 3, it does not thermally expand, and there is a large gap between the thermal expansion portion E and the Height difference.

On the other hand, since the region in the rotation direction R of the drum that is more rearward than the closest point P of the cooling drums 11 and 11 is located in the molten steel groove portion 16, it will thermally expand due to contact with the molten steel 3, but depending on the molten steel At the contact time of 3, the amount of thermal expansion gradually decreases toward the rear side of the drum rotation direction R. Therefore, although the side weir 15 is in contact with the cooling drums 11 and 11 in an inclined state, a large gap is not generated.

In this state, the rotation of the cooling drums 11, 11 is started. At this time, as also shown in FIG. 5(c), the area behind the rotation direction R of the drums 11 and 11 closest to the closest point P of the cooling drums 11 has thermal expansion, but the amount of thermal expansion increases with the direction of the drum rotation direction R. Gradually getting smaller on the rear side, Therefore, although the side weir 15 contacts the cooling drums 11 and 11 in an inclined state, a large gap is not generated.

Further, when the cooling drum 11 is further rotated, the thermal expansion portion E (the part located at the closest point P (roller contact point) of the cooling drums 11 and 11 when the cooling drum 11 has stopped when the casting starts) is slipped with the side weir 15 As shown in FIG. 5( d ), a gap is created between the side weir 15 and the cooling drum 11 when the area is connected. Here, when the size of the gap becomes, for example, 0.2 mm or more, the molten steel 3 will run into this gap.

Here, at the start of casting, as shown in FIG. 4, a raw metal M is formed on the surface of the side weir 15, and the molten steel 3 that runs into the gap between the side weir 15 and the cooling drum 11 solidifies and merges with the above-mentioned raw material The metal M is integrated and bites between the cooling drums 11 and 11.

The portion where the raw metal M bites between the cooling drums 11 and 11 makes the sheet thickness of the slab locally thicker in the width direction and in the longitudinal direction.

Therefore, in this embodiment, the pressure control of the cooling drums 11 and 11 is divided into the following steps: (a) The first step: from the state where the pair of cooling drums 11 and 11 have been stopped to cooling the pair The rotation of the drums 11 and 11 starts, and the wall thickness of the slab 1 passes through the closest point P (roller contact point) of the pair of cooling drums 11 and 11; (b) Step 2: From the first step to the cooling Until the drums 11, 11 rotate more than one revolution; and (c) the third step after the second step.

Hereinafter, each step will be described with reference to FIG. 6 which is an explanatory diagram showing the pressure control method of the cooling drum.

(Step 1)

First, in the first step, as shown in FIG. 6(a), by the hydraulic cylinders 21A and 21B disposed on one end side and the other end side of the pair of cooling drums 11 and 11 in the rotation axis direction, A predetermined pressure (first pressure) presses the pair of cooling rollers 11 and 11 toward each other.

In this embodiment, as shown in FIG. 6(a), hydraulic cylinders 21A, 21B are arranged on the moving side cooling drum 11a, and the moving side cooling drum 11a is directed toward the fixed side cooling drum 11b to press. In addition, although the hydraulic cylinders 21A and 21B are fixed to the side of the pillar, the pillar is not shown for simplicity.

The first pressure is aimed at a value as high as possible within the range that does not affect the startup of the cooling drum 11, but its specific value is mainly based on the width, diameter, type of molten metal, and maximum driving force of the cooling drum 11 To decide. In reality, because it is difficult to find an appropriate value in advance calculations, etc., an appropriate value is found and set in an actual experiment.

(Step 2)

Next, in the second step, as shown in FIG. 6(a), by the hydraulic cylinders 21A and 21B disposed on one end side and the other end side of the pair of cooling drums 11 and 11 in the rotation axis direction, A predetermined pressure (second pressure) presses the pair of cooling drums 11 and 11 toward each other.

In addition, although the second pressure is aimed at a value as high as possible within a range that does not cause deformation or damage to the surface of the cooling drum 11, it mainly depends on the width, diameter, surface shape, and surface material of the cooling drum 11. The type of molten metal and the maximum roll shrinkage are determined. In reality, similar to the first pressure, an appropriate value is obtained and set in an actual experiment.

Here, the second pressure in the second step is set to be higher than the first pressure in the first step.

In other words, in the first step and the second step, the hydraulic cylinders 21A and 21B disposed on one end side and the other end side of the pair of cooling drums 11 and 11 in the rotation axis direction are With the same pressure, the pair of cooling drums 11 and 11 are pressed in the direction approaching each other. Therefore, as described above, even if biting of the raw metal M occurs, the cooling rollers 11 and 11 are pressed toward each other.

Furthermore, in this case, although the "same pressure" allows an error of 10%, in order to start the casting more stable, the error range should be managed to allow 5% or less, preferably 1% or less.

(Step 3)

Next, in the third step, as shown in FIG. 6(b), pressure control is performed so that the total value of the reaction forces at one end side and the other end side of the pair of cooling drums 11 and 11 in the rotation axis direction becomes predetermined Value, and keep the rotation axes of the pair of cooling drums 11 and 11 parallel.

Specifically, as shown in FIG. 6(b), hydraulic cylinders 21A and 21B are arranged on the cooling drum 11a on the moving side, and a load cell is arranged on the cooling drum 11b on the fixed side 22A, 22B. In addition, although the load cells 22A and 22B are fixed to the side of the pillar, the pillar is not shown for simplicity. Send the reaction force signal measured by the load cell 22A, 22B to the reaction The force control unit 24 and in this reaction force control unit 24 give commands so that the total load becomes a predetermined value to advance and retreat the hydraulic cylinders 21A and 21B.

Thereby, the mutually rotating shafts of the pair of cooling drums 11 and 11 are kept parallel, and the slab 1 whose plate thickness is controlled can be manufactured. Furthermore, although the predetermined value of the aforementioned total load is aimed mainly at satisfying the quality of the slab 1 and maintaining the stability of the operation, it is mainly determined by the width, diameter and type of molten metal of the cooling drum 11 . In reality, similar to the first pressure and the second pressure, an appropriate value is obtained and set in an actual experiment.

Here, in the second step, the period from the first step to the rotation of the cooling drum 11 two or more times is preferably used.

However, when the timing of switching from the second step to the third step is delayed, the initial defect amount until the slab 1 subjected to the sheet thickness control is obtained increases, so it is preferable to switch to the third position before the cooling drum 11 rotates 3 times 3 steps.

According to the method of manufacturing the slab 1 of the present embodiment configured as described above, in the second step from the first step to the time when the cooling drums 11 and 11 rotate more than one revolution, since it is arranged by a The hydraulic cylinders 21A and 21B on the one end side and the other end side of the rotating shafts of the cooling drums 11 and 11 are pressed in a direction in which the pair of cooling drums 11 and 11 approach each other at a predetermined pressure (second pressure). The thermal expansion portion E of the cooling drum 11 is located in an area slidingly contacting the side weir 15, and a gap is generated between the side weir 15 and the cooling drum 11. Therefore, even when the molten steel 3 runs into this gap and the entrapment of the raw metal M occurs, the pair of cooling drums 11, 11 is pressed toward each other, and the solidified shell layers 5 and 5 can be sufficiently rolled to each other at the closest point P (roller contact point) of the pair of cooling rollers 11 and 11. Therefore, the unsolidified portion at the center of the thickness of the slab 1 is hardly formed, and the strength of the slab can be maintained. Thereby, the fracture of the cast piece 1 can be suppressed, and casting can be started stably.

In addition, in the method for manufacturing the slab 1 of the present embodiment, since the pair of cooling drums 11 and 11 is stopped to start the rotation of the pair of cooling drums 11 and 11, the wall thickness of the slab 1 is allowed In the first step up to the closest point P (roller contact point) of the pair of cooling drums 11 and 11, the oil disposed on one end side and the other end side of the pair of cooling drums 11 and 11 in the rotation axis direction The cylinders 21A and 21B are pressed toward the pair of cooling rollers 11 and 11 at a relatively low first pressure, so that the thickness portion of the slab 1 formed at the start of casting can be relatively stable By cooling between the drums 11 and 11, the influence on casting can be suppressed.

In the second step, since the cooling drum 11 is pressed with a second pressure higher than the first pressure in the first step, the closest point P (drum contact) of the pair of cooling drums 11 and 11 can be Point) The solidified shell layers 5, 5 are sufficiently rolled against each other. Therefore, the unsolidified portion in the central portion of the thickness of the cast piece 1 is hardly formed, and the strength of the cast piece can be maintained.

Furthermore, in the present embodiment, when the second step is set to a period from the first step to the rotation of the cooling drum 11 two or more times, the above-mentioned thermal expansion portion remains even after the second step E, and biting of the raw metal M occurs, the solidified shell layers 5 and 5 may be sufficiently rolled at the closest point P (roller contact point) of the pair of cooling rollers 11 and 11 Shrink. Thereby, the fracture of the cast piece 1 can be suppressed, and casting can be started stably.

Although the method for manufacturing the slab according to the embodiment of the present invention has been specifically described above, the present invention is not limited to this, and can be appropriately modified within the scope not departing from the technical idea of the invention.

In the present embodiment, although the double-drum type continuous casting apparatus shown in FIG. 1 is taken as an example for description, it is not limited to this.

In addition, the pressing method of the cooling drum is not limited to the case shown in FIG. 6 as long as it is a structure that can perform pressure control as shown in the embodiment.

Examples

Hereinafter, the results of experiments conducted to confirm the effects of the present invention will be described.

The double-drum type continuous casting device shown in FIG. 1 was used, and a cast piece formed of carbon steel with a carbon content of 0.05 mass% was manufactured.

Here, the diameter of the cooling drum is 600 mm, and the width of the cooling drum is 400 mm. In addition, the thickness of the slab cast stably was 2.0 mm.

In Example 1 of the present invention, the switching from the first step to the second step was performed when the number of rotations of the cooling drum was 0.1, and at the time when the number of rotations of the cooling drum was 1.3 Switch from step 2 to step 3.

In Example 2 of the present invention, the switching from the first step to the second step was performed when the number of rotations of the cooling drum was 0.1, and at the time when the number of rotations of the cooling drum was 2.3 From step 2 to step 3 Switch.

In the comparative example, when the number of rotations of the cooling drum is 0.1, the switching from the first step to the second step is performed, and when the number of rotations of the cooling drum is 0.4, the second Switch from step to step 3. Furthermore, in this case, the switching from the second step to the third step corresponds to the time point at which the shell flushing ends.

In addition, in Examples 1, 2 and Comparative Examples of the present invention, the number of breaks and the number of breaks of the slab during the first to second rotations of the cooling drum were evaluated. Table 1 shows the evaluation results.

In addition, the change in the roller reaction force and the roller gap in the comparative example is shown in FIG. 7, and the change in the roller reaction force and the roller gap in Example 1 of the present invention is shown in FIG. 8.

In the comparative example, the breaking rate of the slab during the first to second rotations of the cooling drum was 25%, and the beginning of casting tended to be unstable.

On the other hand, in Examples 1 and 2 of the present invention, the breaking rate of the slab during the first to second rotations of the cooling drum was 0%.

In the comparative example, as shown in FIG. 7, when the raw metal is bitten into WS (Work Side), the roller gap of DS (Drive Side) conforms to WS, and at this time, in DS Medium will greatly reduce the reaction force of the drum, and make the contact between the cooling drum and the solidified shell unstable, and the cooling becomes insufficient.

In contrast, in Example 1 of the present invention, as shown in FIG. 8, even at the time when WS bites into the raw metal, the reaction force of the drum is not reduced at DS, but the solidified shells are strongly Crimping makes the roller gap of DS smaller. Therefore, the unsolidified portion at the center of the thickness of the slab hardly exists, and the surface temperature of the slab becomes relatively low, and the strength of the slab can be maintained. By this, the fracture of the cast piece can be suppressed.

From the above results, according to the method for manufacturing a slab of the present invention, it has been confirmed that it is possible to provide a caster that can suppress the breakage of the slab and can start casting stably in a twin-roller continuous casting device片的制造方法。 The manufacturing method of tablets.

Industrial availability

According to the present invention, it is possible to provide a method of manufacturing a slab that can suppress the breakage of a slab and can start casting stably in a twin-roller continuous casting device.

1: casting

3: molten steel (molten metal)

5: solidified shell

10: Double drum continuous casting device

11: Cooling roller

13: pinch roller

15: Side Weir

16: Molten steel tank part (Molten metal storage part)

18: feeding trough

19: Dipping nozzle

R: direction of drum rotation

Claims (2)

A method of manufacturing slabs is to supply molten metal to a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs, and to form a solidified shell on the peripheral surface of the pair of cooling drums and The method for manufacturing the slab is to grow to produce the slab, characterized in that in the first step, one end side and the other end side of the pair of cooling drums in the rotation axis direction are directed toward the aforesaid with the same first pressure The pair of cooling rollers are pressed in the direction of approaching each other, wherein the first step is to cast the molten metal formed when the molten metal is supplied to the molten metal storage portion in a state where the pair of cooling rollers have been stopped at the start of casting The thickness portion of the sheet is the step after the rotation of the cooling drum is started until it passes the closest point of the pair of cooling drums, and the second step from the first step to the rotation of the pair of cooling drums by more than one revolution In the step, one end side and the other end side of the pair of cooling drums in the rotation axis direction are pressed against each other at a second pressure that is the same and higher than the first pressure, toward In the third step after the second step, pressure control is performed so that the total value of the reaction forces at one end and the other end of the pair of cooling drums in the rotation axis direction becomes a predetermined value, and the pair of cooling drums The mutual axes of rotation are kept parallel. The method for manufacturing a cast piece according to claim 1, wherein the second step is a period from after the first step to when the pair of cooling drums rotates two or more times.

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