JP2018103196A - Thin slab production device and thin slab production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin slab production device and a thin slab production method, even in the case casting is started by a holding start method, capable of stably performing the casting.SOLUTION: Provided is a thin slab production device 10 comprising a pair of rotating cooling drums 11, 11 and a pair of side weirs, in which a molten metal is fed to a molten metal sump part formed by the pair of cooling drums 11, 11 and the pair of side weirs, and a solidified shell is formed and grown at the circumferential face of the cooling drum to produce a thin slab, the device including a preheating apparatus 30, before the start of the casting, in a state of stopping the rotating of the cooling drums 11, locally heating a region upper than a position at which a discharge flow from a molten metal pouring nozzle is collided in the circumferential faces of the cooling drums 11.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a thin-walled slab manufacturing apparatus and a thin-walled slab manufacturing method for supplying a molten metal to a molten-metal pool formed by a pair of cooling drums and a pair of side dams to manufacture a thin-walled slab. It is.

As a method for producing a thin metal slab, for example, as shown in Patent Documents 1 and 2, a cooling drum having a water-cooling structure is provided inside, and a molten metal pool portion formed between a pair of rotating cooling drums is used. Molten metal is supplied, solidified shells are formed and grown on the peripheral surface of the cooling drum, the solidified shells formed on the peripheral surfaces of the pair of cooling drums are joined to each other at the drum kiss point, and pressed down to have a predetermined heat. A manufacturing method using a twin drum type continuous casting apparatus for manufacturing a thin cast slab is provided. The manufacturing method using such a twin drum type continuous casting apparatus is applied to various metals.
Here, in Patent Documents 1 and 2, the cooling drum is heated or cooled in a region opposite to the molten metal reservoir in order to suppress deformation due to thermal expansion of the cooling drum and perform stable casting. It is configured as follows.

There are a flying start method and a holding start method as methods for starting casting in the twin drum type continuous casting apparatus described above.
In the flying start method, molten metal is poured while the cooling drum is rotated. In this case, unsound slab shape due to unstable hot water flow immediately after the start of pouring could not be avoided.
On the other hand, in the holding start method, since the cooling drum starts rotating after accumulating molten metal, the solidified shell is sufficiently formed and then the cooling drum is rotated. Unhealthy shape can be suppressed.

JP 05-092239 A JP 2011-020126 A

  Here, the situation when casting is started by the holding start method will be described with reference to FIGS. In the holding start method, until the molten metal 3 accumulates, the discharge flow from the pouring nozzle 18 collides with a specific portion of the peripheral surface of the cooling drum 11, so that as shown in FIG. A part of the peripheral surface of 11 is thermally expanded locally to form a drum protrusion 35 protruding outward in the radial direction. The drum protrusion 35 formed by the thermal expansion at this time protrudes from the peripheral surface of the cooling drum 11 by about 0.1 mm. Since the pair of cooling drums 11 and 11 protrudes by 0.1 mm, the gap between the cooling drums 11 and 11 changes by 0.2 mm in total.

Next, as shown in FIG. 6 (2), the cooling drums 11 and 11 are rotated while the molten metal 3 is stored. At this time, the collision of the discharge flow from the pouring nozzle 18 is alleviated by the stored molten steel metal 3, and the local thermal expansion of the cooling drum 11 is alleviated. In addition, in the part which stored the molten metal 3, the thickness of the thin slab 1 once thickens, and the initial enlarged part 1a is formed. When the initial enlarged portion 1a passes between the cooling drums 11 and 11, the gap between the cooling drums 11 and 11 widens, so that the drum protruding portion 35 also passes between the cooling drums 11 and 11 without any significant problem. Become.
Next, as shown in FIG. 6 (3), the discharge hole of the pouring nozzle 18 is immersed in the molten metal 3 to be in a steady state. The solidified shell 5 formed on the peripheral surfaces of the pair of cooling drums 11, 11 is pressed to form a thin cast piece.

When the cooling drums 11 and 11 are rotated once and the drum protrusion 35 reaches the drum kiss point again, the cooling drums 11 and 11 are moved backward as shown in FIG. Once spread.
After the drum protrusion 35 passes the drum kiss point, as shown in FIG. 7 (5), the cooling drums 11 and 11 move forward and the gap between the cooling drums 11 and 11 returns to the original state. Since the shape of the rear side in the drum rotation direction is abruptly changed, the movement of the cooling drums 11 and 11 cannot catch up, the thin slab 1 cannot be sufficiently reduced, and the solidified shells 5 and 5 are pressed. The part which becomes inadequate arises.
And as shown in FIG. 7 (6), the plate | board thickness enlarges the location where the crimping | compression-bonding of the solidification shells 5 and 5 is inadequate. The hot molten metal 3 is confined inside the portion that has not been pressure-bonded, and there is a risk that the thin-walled cast slab 1 will break due to reheating.

Here, in the thin-walled slab manufacturing apparatus and the thin-walled slab manufacturing method described in Patent Documents 1 and 2, the deformation of the cooling drum in a steady state is suppressed. The problem cannot be suppressed.
In addition, in order to suppress local deformation of the cooling drum, when the molten metal is quickly accumulated and the pouring nozzle is immersed quickly, the discharge amount and discharge flow rate of the molten metal increase, Local deformation may be promoted. On the other hand, when the molten metal is poured slowly, the time during which the molten metal discharge flow collides may increase, and local deformation may be promoted. Thus, the above-mentioned problem could not be solved simply by adjusting the molten metal pouring conditions.

  The present invention has been made in view of the above-described situation, and is a thin-walled slab manufacturing apparatus and thin-wall casting that can stably perform casting even when casting is started by the holding start method. It aims at providing the manufacturing method of a piece.

  In order to solve the above-described problems, a thin-walled slab manufacturing apparatus according to the present invention has a pair of rotating cooling drums and a pair of side weirs, and a fusion formed by the pair of cooling drums and the pair of side weirs. A thin-walled slab manufacturing device that supplies molten metal to a metal reservoir through a pouring nozzle and forms and grows a solidified shell on the peripheral surface of the cooling drum to manufacture a thin-walled slab before the start of casting And a preheating device that locally heats a region above the position where the discharge flow from the pouring nozzle collides in the peripheral surface of the cooling drum in a state in which the rotation of the cooling drum is stopped. It is said.

  According to the thin-walled slab manufacturing apparatus having this configuration, from the position where the discharge flow from the pouring nozzle collides with respect to the peripheral surface of the cooling drum in a state where the rotation of the cooling drum is stopped before the start of casting. Since the preheating device that locally heats the upper region is provided, the portion on the rear side in the drum rotation direction of the drum protrusion can be thermally expanded in advance. Thereby, when the drum protrusion is formed, the shape of the drum protrusion on the rear side in the drum rotation direction becomes gentle, and when the drum protrusion passes the drum kiss point in the first rotation of the cooling drum, the cooling drum is It will move smoothly and the thin-walled slab can be sufficiently reduced. Thereby, it can suppress that an unsolidified part arises in the inside of a thin cast piece, and can suppress the fracture | rupture of a thin cast piece.

Here, in the apparatus for manufacturing a thin cast piece according to the present invention, it is preferable that the preheating device is removable after the preheating is completed.
In this case, since the preheating device can be removed after the cooling drum is preheated by the preheating device, it is possible to prevent the molten metal from coming into contact with the preheating device at the time of casting, and to suppress deterioration of the preheating device. Moreover, after removing a preheating apparatus, a pouring nozzle and a chamber can be installed, and the workability | operativity fall of a casting start preparation work can be suppressed.

Moreover, in the apparatus for manufacturing a thin cast piece according to the present invention, the preheating device is preferably an IH heater system.
In this case, a part of the peripheral surface of the cooling drum can be locally heated in a short time. Therefore, the rear side in the drum rotation direction of the drum protrusion can be heated accurately and thermally expanded, and when the drum protrusion passes the drum kiss point in the first rotation of the cooling drum, the cooling drum is smoothly moved. And the thin cast slab can be sufficiently reduced.

  According to the thin-walled slab manufacturing method of the present invention, molten metal is supplied to a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs via a pouring nozzle, and the periphery of the cooling drum is A method for producing a thin-walled cast slab by forming and growing a solidified shell on a surface to produce a thin-walled cast slab, wherein before the start of casting, Having a preheating step of heating the region above the position where the discharge flow from the pouring nozzle collides, and then supplying the molten metal from the pouring nozzle in a state where rotation of the cooling drum is stopped, Casting is started in a state where the molten metal is stored.

  According to the method for producing a thin cast piece having this configuration, from the position where the discharge flow from the pouring nozzle collides with respect to the peripheral surface of the cooling drum in a state where the rotation of the cooling drum is stopped before the start of casting. Since it has the preheating process which heats an upper area | region, the part of the drum protrusion direction back side of the drum rotation direction can also be thermally expanded. As a result, the shape of the drum protruding portion on the rear side in the drum rotation direction becomes smooth, and the cooling drum moves smoothly when the drum protruding portion passes the kiss point in the first rotation of the cooling drum. Can be sufficiently reduced. Thereby, it can suppress that an unsolidified part arises in the inside of a thin cast piece, and can suppress the fracture | rupture of a thin cast piece.

Here, in the manufacturing method of the thin cast piece which concerns on this invention, it is preferable to change heating temperature in the circumferential direction of the said cooling drum in the said preheating process.
In this case, in the preheating step, the amount of thermal expansion of the cooling drum can be adjusted by changing the heating temperature in the circumferential direction of the cooling drum, and the shape of the drum protruding portion on the rear side in the drum rotation direction is accurately controlled. be able to.

  As described above, according to the present invention, there is provided a thin-walled slab manufacturing apparatus and a thin-walled slab manufacturing method capable of performing stable casting even when casting is started by the holding start method. can do.

It is explanatory drawing which shows the manufacturing apparatus of the thin cast slab which is embodiment of this invention. FIG. 2 is an enlarged explanatory view around a molten steel pool portion in FIG. 1. It is explanatory drawing which shows the state which installed the preheating apparatus in the manufacturing apparatus of the thin cast piece shown in FIG. It is explanatory drawing which shows the condition at the time of the casting start in the manufacturing method of the thin cast slab which is embodiment of this invention. It is a graph which shows the shape of the drum protrusion part in an Example. (A) is a comparative example, (b) is an example of the present invention. It is explanatory drawing which shows the condition at the time of the casting start in the manufacturing method of the conventional thin cast piece. It is explanatory drawing which shows the condition at the time of the casting start in the manufacturing method of the conventional thin cast piece.

Below, the manufacturing method of the thin cast slab and the manufacturing apparatus of a thin cast slab which are embodiments of the present invention are explained with reference to the attached drawings. In addition, this invention is not limited to the following embodiment.
Further, in the present embodiment, molten steel is used as the molten metal, and the thin cast slab 1 made of a steel material is manufactured.

  As shown in FIG. 1, the thin-walled slab manufacturing apparatus 10 according to the present embodiment supports a pair of cooling drums 11 and 11, bender rolls 12 and 12 that bend the thin-walled slab 1, and the thin-walled slab 1. Pinch rolls 13, a pair of cooling drums 11, a side weir 15 disposed at an end in the width direction, and a molten steel pool portion defined by the pair of cooling drums 11, 11 and the side weir 15 A tundish 17 that holds the molten steel 3 supplied to 16 and a pouring nozzle 18 that supplies the molten steel 3 from the tundish 17 to the molten steel pool portion 16 are provided.

  In the thin cast slab manufacturing apparatus 10, the solidified shells 5, 5 grow on the peripheral surfaces of the cooling drums 11, 11 by cooling the molten steel 3 in contact with the rotating cooling drums 11, 11. The solid cast shells 5, 5 formed on the pair of cooling drums 11, 11 are pressed against each other at the drum kiss point P, whereby the thin cast slab 1 having a predetermined thickness is cast.

  FIG. 2 is an enlarged explanatory view around the molten steel pool 16 in FIG. In the thin cast slab manufacturing apparatus 10 according to this embodiment, a chamber 20 is disposed above the molten steel pool 16 and the cooling drums 11 and 11.

And in the thin cast piece manufacturing apparatus 10 which is this embodiment, the holding start method which starts rotation of the cooling drum 11 after accumulating the molten steel 3 to some extent is employ | adopted as a method of starting casting.
Here, in the thin cast slab manufacturing apparatus 10 according to the present embodiment, as shown in FIG. 3A, the circumferential surface of the cooling drum 11 is stopped in a state in which the cooling drum 11 stops rotating before the start of casting. Among them, a preheating device 30 for locally heating a region above the position where the discharge flow from the pouring nozzle 18 collides is provided.

As shown in FIG. 3B, the preheating device 30 is arranged at the center in the width direction of the cooling drum 11, and is configured not to heat the region E at least 50 mm from the end of the cooling drum 11. Yes.
In the present embodiment, the preheating device 30 is an IH heater system. In the present embodiment, the preheating device 30 is detachable. The preheating device 30 is installed before the start of casting to heat the cooling drum 11, and after heating for a predetermined time, the preheating device 30 is removed, and FIG. As shown in FIG. 3, the chamber 20 and the pouring nozzle 18 can be installed.
Furthermore, in the present embodiment, the preheating device 30 can be adjusted so that the heating temperature changes in the circumferential direction of the cooling drum 11.

In the present embodiment, the position where the discharge flow from the pouring nozzle 18 collides is shown in FIG. 3A when the depression angle from the drum kiss point P is represented by θ as seen from the axial direction of the cooling drum 11. The position is θ = 40 °. The position where the discharge flow from the pouring nozzle 18 collides can be calculated in advance geometrically and mechanically according to the position of the discharge hole of the pouring nozzle 18, the outer diameter of the cooling drum 11, the discharge flow velocity, and the like. .
And the position where the preheating apparatus 30 is arrange | positioned is made into the range of (theta) = 40 degrees-90 degrees. The preheating device 30 is preferably disposed at a position not less than θ at which the discharge flow from the pouring nozzle 18 collides and within a range of θ = 85 ° or less. It is further preferable that the collision position is in the range of θ + 2 ° (42 ° in the present embodiment) and θ = 80 ° or less.

The position of the preheating device 30 in the drum width direction is preferably equal to or greater than the width in which the discharge holes of the pouring nozzle 18 are disposed. Further, as shown in FIG. 3B, the width end position of the preheating device 30 is preferably at least 50 mm or more from the end of the cooling drum 11, and more preferably 100 mm or more.
In the IH heater type preheating device 30, the end portion cannot be heated sufficiently. Therefore, even if the preheating device 30 is arranged up to the width direction end portion of the cooling drum 11, at least from the end portion of the cooling drum 11. The 50 mm region E can be configured not to be heated.

  Below, the manufacturing method of the thin cast piece which is this embodiment using the manufacturing apparatus 10 of the thin cast piece mentioned above is demonstrated.

As shown in FIG. 4A, the dummy sheet 7 is inserted between the pair of cooling drums 11 and 11. At this time, the pair of cooling drums 11 and 11 are stopped.
In this state, the above-described preheating device 30 is installed above the cooling drums 11 and 11 to preheat the cooling drum 11 (preheating step).
It is preferable that the heating temperature is changed in the circumferential direction of the cooling drum 11, and θ at the position where the heating temperature of the cooling drum by the preheating device 30 becomes the highest is the discharge flow from the pouring nozzle 18. It is preferable to be within the range of θ + 5 ° or more and θ + 10 ° or less of the collision position. In the present embodiment, θ at the position where the heating temperature is highest is 48 °, and is set so that the heating temperature gradually decreases toward the front side and the rear side in the drum rotation direction.

  Here, in the preheating process, since the above-described preheating device is used, a range of θ = 40 ° to 90 ° (preferably θ = 40 ° to 85 °, more preferably θ in the circumferential direction of the cooling drum 11). = Range of 42 ° to 80 °), and in the width direction of the cooling drum 11, the cooling drum 11 is in the range from the width both ends of the cooling drum 11 to the 50 mm position (preferably the range from the width both ends to 100 mm position). The surrounding surface is preheated.

  When the cooling drum 11 is heated by the preheating device 30, the peripheral surface of the cooling drum is thermally expanded as shown in FIG. Here, as described above, the heating temperature of the preheating device 30 is set so that the heating temperature of the portion of θ = 48 ° is the highest, and the heating temperature gradually decreases as it goes forward and backward in the drum rotation direction. Therefore, the preheating protrusion 36 formed by preheating protrudes most at a portion of θ = 48 °, and the protrusion height gradually decreases toward the front side and the rear side in the drum rotation direction.

  After the cooling drum 11 is heated by the preheating device 30 for a predetermined time, the preheating device 30 is removed, and the pouring nozzle 18 is installed. Thereafter, as shown in FIG. 4B, the molten steel 3 is supplied from the pouring nozzle 18 in a state where the rotation of the cooling drum 11 is stopped. Then, at the position where the discharge flow from the pouring nozzle 18 collides, the cooling drum 11 is locally heated, and the drum protrusion 35 is formed by thermal expansion. At this time, as shown in FIG. 4 (2), the preheating protrusion 36 gently inclines the rear portion of the drum protrusion 35 in the rotational direction.

After a certain amount of molten steel 3 is stored, the cooling drums 11 and 11 are rotated. In the first rotation of the cooling drum 11, when the drum protrusion 35 described above passes the drum kiss point P, the cooling drums 11, 11 retreat and the cooling drums 11, 11 as shown in FIG. The gap between becomes larger.
After the drum protrusion 35 has passed the drum kiss point P, as shown in FIG. 4 (4), the cooling drums 11 and 11 move forward to reduce the gap between the cooling drums 11 and 11.
Here, in this embodiment, the preheating protrusion 36 gently slopes the rear side portion of the drum protrusion 35 in the drum rotation direction, and thus follows the shapes of the drum protrusion 35 and the preheating protrusion 36. The cooling drums 11 and 11 move smoothly.

  Thereafter, the cooling drums 11 and 11 are heated by the heat from the molten steel pool portion 16, the influence of the drum protrusion 35 and the preheating protrusion 36 is eliminated, the local thermal expansion is eliminated, and a steady state is obtained. . And the solidified shells 5 and 5 are formed in the surrounding surface of the cooling drums 11 and 11, and these solidified shells 5 and 5 are crimped | bonded in the drum kiss point P, and the thin cast 1 is manufactured.

According to the thin-walled slab manufacturing apparatus 10 and the thin-walled slab manufacturing method according to the present embodiment configured as described above, discharge from the pouring nozzle 18 on the peripheral surface of the cooling drum 11 before the start of casting. Since it has the preheating device 30 which locally heats the region above the position where the flow collides, before the start of casting, the drum rotation direction rear side from the position where the discharge flow from the pouring nozzle 18 collides The preheating protrusion part 36 can be formed in the part, and the inclination of the drum protrusion part 35 formed in the position where the discharge flow from the pouring nozzle 18 collides can be made gentle. Thereby, when the drum protrusion 35 passes the drum kiss point P in the first rotation of the cooling drum 11, the cooling drums 11 and 11 smoothly move so as to follow the shapes of the drum protrusion 35 and the preheating protrusion 36. The thin cast slab 1 can be sufficiently reduced.
Therefore, it can suppress that an unsolidified part arises in the thin slab 1 due to the drum protrusion part 35, and the fracture | rupture of the thin slab 1 can be suppressed.

  Moreover, in the thin-walled slab manufacturing apparatus 10 and the thin-walled slab manufacturing method according to the present embodiment, the preheating device 30 is removable after the preheating is completed. The nozzle 18 and the chamber 20 can be installed, and the workability deterioration of the casting start preparation work can be suppressed. Moreover, it can prevent that the molten steel 3 contacts the preheating apparatus 30 at the time of casting, and can suppress the early deterioration of the preheating apparatus 30.

  Furthermore, in the thin cast slab manufacturing apparatus 10 and the thin cast slab manufacturing method according to the present embodiment, since the preheating device 30 is of the IH heater type, a part of the peripheral surface of the cooling drum 11 is locally applied. It can be heated in a short time. Therefore, the drum rotation direction rear side of the drum protrusion 35 can be accurately heated and thermally expanded, and the shape of the preheating protrusion 36 can be controlled.

  Further, in the thin cast slab manufacturing apparatus 10 and the thin cast slab manufacturing method according to the present embodiment, the heating temperature of the preheating device 30 is the highest in the vicinity of θ = 48 °, and the front of the drum rotating direction is the front. The heating temperature is set so that the heating temperature gradually decreases toward the side and the rear side, and the preheating protrusion 36 formed by preheating protrudes most at the portion of θ = 48 °, and the drum rotation direction front side and rear side Since the protrusion height gradually decreases in the direction toward the head, as a result of being combined with the drum protrusion 35, the rear side in the drum rotation direction of the drum protrusion 35 can be further smoothed. Therefore, when the drum protrusion 35 passes the drum kiss point P in the first rotation of the cooling drum 11, the cooling drums 11 and 11 smoothly move so as to follow the shapes of the drum protrusion 35 and the preheating protrusion 36. The thin cast slab 1 can be sufficiently reduced.

  Furthermore, in the present embodiment, the preheating device 30 causes the cooling drum in the width direction of the cooling drum 11 to be in the range from the width both ends of the cooling drum 11 to the 50 mm position (preferably the range from the width both ends to 100 mm position). 11 is configured to be preheated, it is possible to prevent the preheating protrusion 36 from being formed at the end in the width direction of the cooling drum 11. In addition, since the discharge flow from the pouring nozzle 18 does not directly collide with the end in the width direction of the cooling drum 11 and the drum protrusion 35 is not formed, it is not necessary to provide the preheating protrusion 36. On the contrary, the reduction can be stabilized by not forming the preheating protrusion 36 at the width end portion of the cooling drum 11.

  In the present embodiment, the preheating device 30 causes the cooling drum 11 to have a circumferential direction of θ = 40 ° to 90 ° (preferably θ = 85 ° or less, more preferably θ = 80 ° or less). Since the peripheral surface of the cooling drum 11 is preheated, the region other than the rear side in the drum rotation direction of the drum protrusion 35 is not thermally expanded, and the reduction is stabilized in other regions. Can do.

As mentioned above, although the thin slab manufacturing apparatus and the thin slab manufacturing method according to the embodiment of the present invention have been specifically described, the present invention is not limited to this and departs from the technical idea of the present invention. It is possible to change appropriately within the range not to be.
For example, in the present embodiment, the preheating device has been described as an IH heater method, but the present invention is not limited to this, and other types of preheating devices such as a heater using a siliconite heating element may be applied.
In the present embodiment, the preheating device is described as being removable. However, the present invention is not limited to this, and a system that is always installed may be used as long as it does not interfere with casting.
Furthermore, although this embodiment demonstrated as what was comprised so that heating temperature might be changed in the circumferential direction of a cooling drum, it is not limited to this.

In the following, the results of experiments conducted to confirm the effects of the present invention will be described.
Using the apparatus for manufacturing a thin cast piece shown in FIG. 1, a thin cast piece made of carbon steel having a carbon content of 0.05 mass% was produced.
Here, as the cooling drum, an internal cooling type made of copper with a 1 mm thick Ni plating film formed on the peripheral surface was used. The width of the cooling drum was 1000 mm and the outer diameter was 500 mm. The slab thickness for steady casting was set to 1.5 mm.

  The pouring nozzle used had a discharge hole installation range width of 530 mm and a structure that protrudes molten steel in the horizontal direction. This pouring nozzle was installed so that the molten steel protruded at a position 200 mm above the drum kiss point. As a result, the discharge flow from the pouring nozzle collides with the cooling drum at a depression angle θ = 40 ° from the drum kiss point.

  With the cooling drum stopped, molten steel at 1580 ° C. was poured for 3 seconds, and the molten steel was stored until the discharge hole of the pouring nozzle was immersed, and then rotated at a peripheral speed of the cooling drum of 40 m / min. Piece casting was performed.

In the present invention example, a part of the peripheral surface of the cooling drum was preheated before the start of casting using the IH heater type preheating device described in the embodiment. The width of the preheating device was 900 mm. Moreover, it arrange | positioned so that the area | region of depression angle (theta) = 42 degrees-80 degrees from a drum kiss point may be heated. The heating temperature was set to a maximum temperature of 350 ° C. near θ = 48 °, and the heating temperature was gradually lowered toward the front side and the rear side in the drum rotation direction.
In the comparative example, preheating before the start of casting was not performed.

As a result, in the comparative example, the breakout of the thin cast piece occurred at the first rotation of the cooling drum, and the casting was stopped.
On the other hand, in the example of the present invention, casting could be started without any problem and casting could be performed stably.

  Here, in FIG. 5, the result confirmed about the thermal expansion amount of the cooling drum at the time of a casting start in a comparative example and this invention example is shown. Note that the thermal expansion amount (increase in radius) of the cooling drum was directly measured by a non-contact distance meter (for example, a capacitance displacement meter). The thermal expansion amount of the cooling drum (increase in radius) can also be calculated by measuring the temperature of the peripheral surface of the cooling drum and performing numerical analysis.

In the comparative example in which the preheating of the cooling drum was not performed, as shown in FIG. 5A, the thermal expansion amount was maximized at the position where the discharge flow from the pouring nozzle collides (θ = 40 °). . Further, it is confirmed that the molten steel flows and is thermally expanded also on the lower side (front side in the drum rotation direction) than the collision position of the discharge amount. Then, it is confirmed that the amount of thermal expansion suddenly decreases on the rear side in the drum rotation direction from the position (θ = 40 °) where the discharge flow from the pouring nozzle collides. That is, the rear side in the drum rotation direction of the drum protrusion formed by the collision of the discharge flow from the pouring nozzle is a steep slope.
For this reason, in the comparative example, after the drum protrusion passes the drum kiss point in the first rotation of the cooling drum, there is a portion where the cooling drum does not catch up and the solidified shell is insufficiently pressed, and breakout occurs. Presumed to have occurred.

On the other hand, in the example of the present invention in which the cooling drum is preheated, as shown in FIG. 5B, a preheating protrusion is formed in the depression angle θ = 42 ° to 80 ° region from the drum kiss point by preheating. It was done. The preheating protrusion gradually decreases in height as it goes rearward in the drum rotation direction. Therefore, it is confirmed that the thermal expansion amount is gradually reduced at the rear side in the drum rotation direction from the position (θ = 40 °) where the discharge flow from the pouring nozzle collides. That is, the drum rotation direction rear side of the drum protrusion formed by the collision of the discharge flow from the pouring nozzle is a gentle slope.
For this reason, in the example of the present invention, it is estimated that the cooling drum could be sufficiently crushed and cast stably even after the drum protrusion passed the drum kiss point during the first rotation of the cooling drum. .

  From the above results, according to the thin slab manufacturing method and the thin slab manufacturing apparatus according to the present invention, the thin slab manufacturing method and the thin slab manufacturing apparatus capable of starting casting stably. It was confirmed that it could be provided.

1 Thin-walled slab 3 Molten steel (molten metal)
5 Solidified shell 7 Dummy sheet 10 Thin cast slab manufacturing equipment 11 Cooling drum 16 Molten steel reservoir (molten metal reservoir)
30 Preheating device 35 Drum protrusion 36 Preheating protrusion

Claims (5)

A pair of rotating cooling drums and a pair of side weirs are provided, and a molten metal is supplied to a molten metal reservoir formed by the pair of cooling drums and the pair of side weirs via a pouring nozzle, and the cooling drum A thin-walled slab manufacturing device that forms and grows a solidified shell on a peripheral surface to manufacture a thin-walled slab,
A preheating device that locally heats a region above the position where the discharge flow from the pouring nozzle collides in the peripheral surface of the cooling drum in a state where the rotation of the cooling drum is stopped before the start of casting. An apparatus for producing a thin-walled slab characterized by the above.   The apparatus for producing a thin cast slab according to claim 1, wherein the preheating device is removable after completion of preheating.   3. The apparatus for producing a thin cast slab according to claim 1, wherein the preheating device is an IH heater system. A molten metal is supplied to a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs via a pouring nozzle, and a solidified shell is formed and grown on the peripheral surface of the cooling drum to form a thin wall casting. A method for producing a thin-walled slab for producing a piece,
Before starting casting, with the rotation of the cooling drum stopped, it has a preheating step of heating a region above the position where the discharge flow from the pouring nozzle collides with the peripheral surface of the cooling drum,
Thereafter, the molten metal is supplied from the pouring nozzle while the rotation of the cooling drum is stopped, and the casting is started in a state where the molten metal is stored.   The method for producing a thin cast slab according to claim 4, wherein in the preheating step, a heating temperature is changed in a circumferential direction of the cooling drum.

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