JP4102352B2 - Continuous casting method of molten stainless steel using hot reuse tundish - Google Patents

Description

The present invention relates to a continuous casting method of molten stainless steel using a hot reuse tundish that prevents deterioration of quality due to contamination of slabs and inclusions due to oxidation of residual steel slag and metal in the tundish.

Conventionally, in continuous casting, when pouring of the pre-charge is completed or the steel type to be cast changes, the used tundish is once lowered to the maintenance shop and a new tundish is prepared before the next casting is performed. Is adopted. However, in order to effectively use the retained heat and reduce the cost of refractories, the hot tundish used for casting is repeatedly used for casting molten steel, so-called hot rotating (hot reuse) casting of tundish. Is being adopted.
For example, in Patent Documents 1 and 2, the steel (metal) and slag remaining in the tundish that has been cast is made smaller in amount of oxygen-enriched air than the theoretical air amount that completely burns the fuel. The tundish is reused by melting and removing the ingot and slag in the tundish, and using the tundish in which the ingot and slag are removed and the interior is in a high temperature state for the next casting. Has been.
Moreover, in patent document 3, in order to eliminate problems, such as temperature drop of a molten steel and nozzle blockage resulting from heat shortage, such as preheating of a tundish prior to casting, and temperature rise, the residual molten steel in the tundish is located near the casting position. A slag drainage position is provided, the casting position and the slag position are connected by a rail, and two tundishes can be run on this rail, while the other tundish is cast during the casting of one tundish A tundish hot reuse facility has been proposed in which operations such as evacuation and maintenance are carried out to heat and wait for the next casting.

JP-A-4-238656 JP-A-10-216908 JP-A-5-318052

However, in the inventions described in Patent Documents 1 and 2, the remaining metal that has not been dissolved or removed due to oxidation of the metal even if the oxygen-enriched air is burned at a lower amount than the theoretical air. As a result, the molten steel is contaminated due to the residual slag, so that the quality of the slab is remarkably deteriorated, and the amount of the slab that is degraded is increased.
In the invention described in Patent Document 3, it is difficult to completely discharge molten steel and slag in the tundish at the discharge position, and quality deterioration due to residual metal and residual slag occurs. Furthermore, oxidation of the residual molten steel occurs during the hot standby of the tundish, and the generated oxide contaminates the molten steel poured into the tundish, increasing the amount of slab that falls off the grade. was there.

The present invention has been made in view of such circumstances, and prevents the deterioration of the quality due to contamination of the slab and inclusions due to oxidation of the remaining steel slag and metal in the tundish, and the high quality and high quality of the slab. An object of the present invention is to provide a continuous casting method of molten stainless steel using a hot reuse tundish that enables yield.

In the continuous casting method of the molten stainless steel using the hot reuse tundish according to the present invention, the tundish is tilted from the horizontal state after the sealing lid is installed at the opening of the tundish cover after the continuous casting is finished, After discharging the molten steel and slag until the amount of residual steel slag (mixture of molten steel and slag) in the tundish is in the range of 0.1 to less than 0.6 tons, the tundish is returned to the horizontal and heated. A process of waiting in a state between,
Supplying molten steel into the tank in the dish waiting, after holding the molten steel in a predetermined amount in the tundish, possess a step of starting pouring into the mold from the tundish,
A lower weir having a through-hole formed in the thickness direction at the bottom of the tundish, and a guide block for evacuation for guiding the molten steel and slag blocked by the lower weir when the tundish is tilted to the through-hole And place .

In the continuous casting method of the molten stainless steel using the hot reuse tundish according to the present invention, since the tundish is repeatedly used in the hot state, a large temperature fluctuation is not applied to the refractory constituting the tundish. Refractory damage can be prevented. As a result, the refractory cost can be greatly reduced. In addition, since hot reuse is performed, processes such as drying and preheating are not required, and it is possible to save energy by effectively using sensible heat, while reducing the waiting time for continuous casting and continuous casting. This can improve productivity.

In addition, the amount of residual steel in the tundish after the end of continuous casting is regulated to a range of 0.1 to 0.6 tons, and a predetermined amount of molten steel is held in the tundish before pouring into the mold. Since it starts (holding start), while the molten steel is retained in the tundish, the remaining steel slag in the tundish can be dissolved in the molten steel, and the slag can be lifted and cleaned and retained in the tundish It is possible to clean the molten steel. As a result, it is possible to prevent slab quality deterioration due to the deterioration of slab quality due to contamination by residual steel slag and inclusions, and to keep slab quality down, Yield can be improved.
Furthermore, since the opening of the tundish cover is closed with a sealing lid after the continuous casting is completed, the oxygen concentration in the tundish can be reduced quickly and stably from the time when the molten steel and slag remaining in the tundish are discharged. It can hold | maintain, it becomes possible to prevent the oxidation of the metal in a tundish and to prevent the contamination of the slab obtained by the next continuous casting.

In particular, when the predetermined amount of molten steel held in the tundish is 10 tons or more and 30 tons or less, the remaining steel slag in the tundish can be completely melted and a part of the slag can be floated. While cleaning in a dish can be achieved, generation | occurrence | production of the slab which becomes the quality fall resulting from a contamination and an inclusion can be made small. For this reason, more preferable results are obtained when the molten steel is 15 tons or more and 30 tons or less.
When the overheated temperature of the molten stainless steel supplied to the waiting tundish is 10 ° C. or higher and 60 ° C. or lower, the remaining amount in the tundish is maintained until a predetermined amount of molten stainless steel is held in the tundish. The steel plate can be surely melted and a part of the slag can be lifted. Preferably, when the overheating temperature is in the range of 10 to 60 ° C., the melting and floating of the remaining steel sheet are promoted by increasing the amount of the remaining steel sheet corresponding to the increase in the amount of the remaining steel sheet. Quality deterioration can be prevented.
In addition, a lower weir with a through hole formed in the thickness direction at the bottom of the tundish, and a guide for excretion that guides molten steel and slag that are blocked by the lower weir when the tundish is tilted to the through hole Since the blocks are arranged, it is easy for the molten steel and slag to flow out of the tundish, and the amount of remaining steel in the tundish can be in the range of 0.1 to 0.6 tons.
In this way, hot reuse of tundish due to the molten stainless steel causes the quality of the slab to be contaminated over the long casting period by the remaining steel iron and inclusions resulting from oxidation of the remaining steel iron, resulting in a large amount of quality. A bad slab was generated.
In order to solve this problem, the present invention reduces the amount of residual steel to 0.1 to less than 0.6 tons and a predetermined amount of molten steel to be poured into the tundish, for example, 10 to 30 tons By holding and casting, it was possible to prevent molten steel contamination due to residual steel slag and molten steel contamination due to oxidation, and to improve the yield of good cast slabs and improve the homogeneity of slabs.
In addition, by adjusting the amount of remaining steel and the overheating temperature (superheat) within a predetermined range or according to the amount of remaining steel, the contamination of the molten steel is stably eliminated, and the good slab yield is improved. Improved stability and improved uniformity of cast slabs.
Furthermore, when a stopper is inserted into the molten steel discharge hole of the waiting tundish and the sealing material is filled between the molten steel discharge hole and the stopper, the molten steel is discharged until a predetermined amount of molten stainless steel is retained in the tundish. Leakage of molten stainless steel from the hole can be reliably prevented.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is a side sectional view of a tundish applied to a continuous casting method of molten stainless steel using a hot reuse tundish according to an embodiment of the present invention, and FIG. 2 is arranged at the bottom of the tundish. 3 is an explanatory view of the lower weir and the discharge guide block, FIG. 3 is an explanatory view of the seal lid installed at the opening of the tundish cover of the tundish, and FIG. 4 is between the molten steel discharge hole of the tundish and the stopper. FIG. 5 is a graph showing the relationship between the amount of steel remaining in the tundish and the overheating temperature, and FIG. 6 is a product manufactured from the first and second slabs manufactured in continuous casting. FIG.

As shown in FIG. 1, a tundish 10 applied to a method for continuously casting molten stainless steel using a hot reuse tundish according to an embodiment of the present invention comprises an outer shell, for example, a boat-shaped iron. It has a skin 11, a refractory layer 12 for insole provided inside the bottom of the boat-shaped iron skin 11, and a refractory layer 13 for inner wall provided inside the side of the boat-shaped iron skin 11. . An overflow hole 14 is formed at the center in the width direction on the one side of the refractory layer 13 for the inner wall (the front side of the boat-shaped iron skin 11).
In addition, a molten steel discharge hole 16 that is opened and closed by the entrance and exit of a stopper 15 formed of a refractory material at the center in the width direction on the other side of the insole refractory layer 12 (the rear side of the boat-shaped iron skin 11). In the molten steel discharge hole 16, one end of the upper nozzle 17 is embedded so as to be in smooth contact with the inner surface of the molten steel discharge hole 16, and the other side of the upper nozzle 17 penetrates the bottom of the boat-shaped iron skin 11 And project outside. The other end of the upper nozzle 17 is connected to a sliding nozzle 18 communicating with a mold (not shown) and an immersion nozzle (not shown) below the sliding nozzle 18. With such a configuration, the molten stainless steel is poured into the mold from the molten steel discharge hole 16 through the sliding nozzle 18 and the immersion nozzle while supplying the molten stainless steel into the tundish 10 with the long nozzle 19 for continuous casting. It can be carried out.

Here, at the position closer to the molten steel discharge hole 16 than the central portion of the refractory layer 12 for the insole, as shown in FIG. Is formed with a notch on both sides on the lower end side, and the lower end of the center excluding the notch is connected to the refractory layer 12 for the insole. Accordingly, through holes 21 surrounded by the respective surfaces of the notch, the insole refractory layer 12 and the inner wall refractory layer 13 are formed in both sides of the lower end portion of the lower weir 20 in the thickness direction of the lower weir 20. Can be formed. Further, on the refractory layer 12 for the inlay on the other side of the lower weir 20 (on the opposite side to the overflow hole 14 side), the base end is in contact with the central lower end portion of the lower weir 20, and the tip dimension is the base end. For example, a trapezoidal waste guide block 22 (formed of a refractory material) in a plan view is disposed.

With such a configuration, one side and the other side of the lower weir 20 can be communicated with each other through the through-hole 21, and one side (overflow hole 14) of the tundish 10 comes down after the continuous casting is finished. When the tundish 10 is tilted so that the molten stainless steel remaining in the tundish 10 (hereinafter simply referred to as molten steel) and slag are discharged from the overflow hole 14, the other side of the lower weir 20 The dammed molten steel and slag can be moved to one side of the lower weir 20 through the through hole 21 and can be discharged from the overflow hole 14.
At this time, since the evacuation guide block 22 is disposed on the refractory layer 12 for the inlay on the other side of the lower weir 20, it remains on the other side of the lower weir 20 when the tundish 10 is tilted. The molten steel and slag can be guided to the respective through holes 21 while being moved along the side end face 23 of the discharge guide block 22. As a result, when the tundish 10 is tilted to discharge the molten steel and slag, the amount of residual steel in the tundish 10 can be reduced as much as possible.
Here, the remaining steel slag refers to slag, slag and metal, or those containing a partially molten steel.

Here, when the length (trapezoidal height) H of the evacuation guide block 22 is constant, the angle θ between the base end of the evacuation guide block 22 and the side end face 23 is 50 to 60 °. It is preferable to set to. When the angle θ exceeds 60 °, the length of the tip of the waste guide block 22 (the trapezoidal upper base) increases, the amount of molten steel and slag adhering to the tip increases, and the remaining steel plate in the tundish 10 Since the amount increases, it is not preferable. On the other hand, when the angle θ is less than 50 °, the force for moving the molten steel and slag adhering to the side end surface 23 along the side end surface 23 is reduced, and the amount of molten steel and slag guided to the through hole 21 is reduced. This is not preferable because the amount of remaining steel in the dish 10 increases.
The length H of the evacuation guide block 22 is set to, for example, a range of 0.5 to 0.9 times the length of the base end of the evacuation guide block 22 (the bottom base of the trapezoid). It is good to do. If the length H of the waste guide block 22 is less than 0.5 times the length of the base end of the waste guide block 22, the region where the molten steel and slag can be guided approaches the waste guide block 22 and is wide. The molten steel and slag cannot be induced, which is not preferable. On the other hand, if the length H of the waste guide block 22 exceeds 0.9 times the length of the base end of the waste guide block 22, the surface area of the waste guide block 22 increases and the remaining steel plate Since the amount of steel remaining in the tundish 10 increases due to adhesion, it is not preferable.

Above the inner refractory layer 12 on one side of the lower weir 20, an upper weir 24 (formed of a refractory material is formed with a gap between the lower weir 20 and both ends connected to the inner wall refractory layer 13. Is provided). Here, the lower weir 20 and the upper weir 24 are configured such that the height position of the upper end of the lower weir 20 is higher than the height position of the lower end of the upper weir 24.
By adopting such a configuration, when the molten steel is supplied into the tundish 10 via the long nozzle 19 and the stopper 15 is pulled up to cause the molten steel to flow out of the molten steel discharge hole 16, the amount of molten steel that has flowed out of the molten steel discharge hole 16 Therefore, an amount of molten steel corresponding to 1 is supplied from one side of the upper weir 24 to the other side. At this time, the molten steel existing on one side of the upper weir 24 collides with the lower weir 20 and becomes an upward flow that rises through the gap between the upper weir 24 and the lower weir 20 and reaches the other side of the upper weir 24. Inclusions mixed in the molten steel can easily float along the flow of the molten steel. For this reason, molten steel with few inclusions can flow out from the molten steel discharge hole 16.

Further, the tundish 10 includes a tundish cover 25 that covers the tundish 10 from above. The tundish cover 25 has an iron skin 26 that forms the upper part of the tundish cover 25, and a wall refractory layer 27 provided inside the iron skin 26. Further, the tundish cover 25 is an example of an opening formed through the iron skin 26 and the wall refractory layer 27, and is a long nozzle opening 28, a stopper opening 29, and a sampling (not shown). An opening is provided. Here, as shown in FIG. 3, a latch member 30 is provided on the other side of the long nozzle opening 28 (opposite to the overflow hole 14 side), and the latch member 30 is an example of a connecting member. A seal lid 33 capable of covering the long nozzle opening 28 is connected via the chain 32. A latching member is also provided on the other side of the sampling opening (not shown), and a seal lid capable of covering the sampling opening is connected to the latching member via a chain.

By adopting such a configuration, even when the tundish cover 25 is attached to the tundish 10, the stopper 15 can be inserted into and exited from the molten steel discharge hole 16 by inserting the stopper 15 from the stopper opening 29. Further, the long nozzle 19 can be inserted from the long nozzle opening 28 to supply molten stainless steel into the tundish 10. Thus, continuous casting can be performed while keeping the oxygen concentration in the tundish 10 low.
Further, after the continuous casting is finished, the stopper 15 is raised halfway, the long nozzle 19 is pulled up, the long nozzle opening 28 is used as the long nozzle opening seal lid 33, and the sampling opening is used as the sampling opening. The oxygen concentration in the tundish 10 can be quickly reduced (for example, 1% or less) from the time when the molten steel and slag are discharged, and can be stably maintained. It is possible to prevent the oxidation of bullion. The seal lid 33 is connected to the latch member 30 via the chain 32, and the seal lid for the sampling opening is also connected to the latch member via the chain, so that the tundish 10 is tilted. Also, the seal lid 33 that closes the long nozzle opening 28 and the seal lid that closes the sampling opening do not fall off.

Next, a continuous casting method of molten stainless steel using a hot reuse tundish according to an embodiment of the present invention will be described.
When the continuous casting is completed, as shown in FIG. 1, the tundish 10 supported in a horizontal state is inserted from the long nozzle opening 28 and the stopper opening 29 provided in the tundish cover 25, respectively. The long nozzle 19 is pulled out, the stopper 15 is raised halfway, and the seal lid 33 placed on the other side of the long nozzle opening 28 and the seal lid placed on the other side of the sampling opening are removed. The long nozzle opening 28 is moved by the sealing lid 33 and the sampling opening is closed by the sampling opening sealing lid.

Next, the tundish 10 is tilted so that the overflow hole 14 of the tundish 10 comes down with the tundish cover 25 covered, and the molten steel and slag remaining in the tundish 10 are removed from the overflow hole 14. It discharged to the outside from.
At this time, the molten steel and slag present on one side of the lower weir 20 move on the refractory layer 12 for the inlay and the refractory layer 13 for the inner wall and are discharged from the overflow hole 14. Further, the molten steel and slag existing on the other side of the lower weir 20 are dammed on the other side of the lower weir 20 and moved to one side of the lower weir 20 through the through hole 21, and on the refractory layer 12 for the insole and It moves on the inner wall refractory layer 13 and is discharged from the overflow hole 14. Here, since the evacuation guide block 22 is disposed on the refractory layer 12 for the inlay on the other side of the lower weir 20, it remains on the other side of the lower weir 20 when the tundish 10 is tilted. The molten steel and slag can be guided to the respective through holes 21 while being moved along the side end face 23 of the discharge guide block 22. Thereby, the molten steel and slag remaining on the other side of the lower weir 20 can be easily discharged.

Here, the amount of steel remaining in the tundish 10 when the tundish 10 is tilted and the discharge of the molten steel and the slag is finished is 0.1 ton or more and less than 0.6 ton. Even if the tundish 10 is tilted to sufficiently discharge the molten steel and slag, the inner surface of the tundish 10 (the refractory layer 12 for the insole, the refractory layer 13 for the inner wall, the lower weir 20, the upper weir 24, Further, a part of the molten steel or slag adheres to each surface) of the waste guide block 22 and, for example, a residual steel cake amount of about 0.1 ton exists in the tundish 10.
For this reason, the lower limit of the amount of remaining steel defects was made into 0.1 ton. Further, when the amount of residual steel in the tundish 10 becomes 0.6 tons or more, even if a predetermined amount of molten steel is held in the tundish 10, cleaning of the molten steel becomes insufficient, and a cast obtained by continuous casting is obtained. Deterioration in quality due to contamination of the pieces and inclusions becomes significant. For this reason, the amount of steel remaining was made less than 0.6 tons.

The seal lid 33 closing the long nozzle opening 28 is connected to the latching member 30 via the chain 32, and the seal lid closing the sampling opening is also connected to the latching member via the chain. Since they are connected, even if the tundish 10 is tilted, the seal lid 33 that closes the long nozzle opening 28 and the seal lid that closes the sampling opening do not fall off. For this reason, even when the tundish 10 is tilted, the openings such as the long nozzle opening 28 can be reliably closed, and the oxygen concentration in the tundish 10 is quickly reduced and stabilized from the time when the molten steel and slag are discharged. Can be retained.

After the discharge of molten steel and slag in the tundish 10 is finished, the tundish 10 is returned to the horizontal position, and after the treatment of the remaining steel slag on the upper nozzle 17 of the tundish 10 and the minimum repair, etc., it rises halfway. The stopper 15 that has been moved down is lowered and inserted into the molten steel discharge hole 16 to close the molten steel discharge hole 16 and wait in a hot state.
At this time, as shown in FIG. 4, a whisker layer 35 is formed by filling a gap formed between the molten steel discharge hole 16 and the stopper 15 with a whisker (for example, an alumina whisker) as an example of a sealing material. As a result, even if there is a gap between the molten steel discharge hole 16 and the tip of the stopper 15 (for example, metal or slag adheres to the inner surface of the molten steel discharge hole 16 and the tip of the stopper 15 and the molten steel discharge hole 16, the molten steel discharge hole 16 can be reliably closed.

Here, the height L of the whisker layer 35 (the distance from the lowermost position of the gap between the molten steel discharge hole 16 and the stopper 15 to the upper end of the whisker layer 35 ) is preferably 70 to 100 mm. When the height L of the whisker layer 35 is less than 70 mm, when the molten steel is supplied into the tundish 10 with the stopper 15 being inserted into the molten steel discharge hole 16, the molten steel discharge hole 16 and the tip of the stopper 15 It is not preferable because the molten steel easily flows out from a gap existing between them.
On the other hand, when the height L of the whisker layer 35 exceeds 100 mm, when the molten steel is supplied into the tundish 10, the heat insulating state of the tip of the stopper 15 is improved and the tip of the stopper 15 is seized into the molten steel discharge hole 16. When the stopper 15 is pulled up at the start of continuous casting, the tip of the stopper 15 breaks and remains on the molten steel discharge hole 16 side (head drop) phenomenon, which is not preferable.

When resuming continuous casting, the seal lid 33 that closes the long nozzle opening 28 is moved to the other side of the long nozzle opening 28, the long nozzle 19 is inserted from the long nozzle opening 28, Supply of molten steel into the dish 10 is started. Then, after a predetermined amount of molten steel is held in the tundish 10, pouring into the mold is started.
Here, the predetermined amount of molten steel retained in the tundish 10 is 10 to 30 tons. If the amount of molten steel held in the tundish 10 is less than 10 tons, it becomes difficult to completely dissolve the remaining steel slag remaining in the tundish 10 and remove the slag from the surface, and the cleaning of the molten steel is insufficient. Become. For this reason, the deterioration of the quality resulting from contamination and inclusions of the slab obtained by continuous casting becomes remarkable, which is not preferable. On the other hand, when the amount of molten steel retained in the tundish 10 exceeds 30 tons, the amount of molten steel in which the remaining steel iron is melted increases more than necessary. For this reason, many unsatisfactory slabs in which the remaining steel sheet is melted are cast, which is not preferable because the yield of good slabs decreases. For this reason, more preferable results can be obtained when the molten steel amount is 15 tons or more and 30 tons or less.

Moreover, it is preferable that the temperature of the molten steel supplied to the tundish 10 is 10 to 60 ° C. higher than the molten steel temperature during continuous casting, that is, in an overheated state. As a result, the remaining steel slag can be surely dissolved in a predetermined amount of molten steel held in the tundish 10 and the slag can be lifted and removed, and the cleanliness of the molten steel supplied into the tundish 10 can be increased. become.
In addition, it is good to set the overheating temperature of molten steel high within the range of 10-60 degreeC corresponding to the amount of remaining steel defects in the tundish 10 increasing. Thereby, even if the amount of remaining steel in the tundish 10 increases, the remaining steel in the tundish 10 can be surely melted.

Here, when the overheating temperature of the molten steel is less than 10 ° C., the remaining steel slag cannot be completely dissolved while the predetermined amount of molten steel is held, and the remaining steel slag remaining without melting becomes the tundish 10. It will dissolve in the molten steel that is sequentially supplied. For this reason, since the contamination of the molten steel in the tundish 10 by the remaining steel iron continuously occurs and the amount of slabs with poor quality increases, it is not preferable.
On the other hand, if the overheating temperature of the molten steel exceeds 60 ° C., the remaining steel slag in the tundish 10 can be surely melted, but the refractory layer 12 for the insole and the inner wall can be obtained by increasing the temperature of the molten steel. The refractory layer 13, the lower weir 20, the upper weir 24, and the discharge guide block 22 are not preferable because melting damage becomes remarkable. Furthermore, a delay in solidification of the molten steel in the mold occurs, which causes a problem in quality due to temperature deviation, which is not preferable.

The tundish obtained by removing the lower weir 20 from the tundish 10 was repeatedly used continuously, and casting was started without holding a predetermined amount of molten steel in the tundish (hereinafter referred to as case 1). The relationship between the amount of steel remaining in the tundish and the overheating temperature on the quality of the product produced from the slab obtained at this time was obtained, and the remaining steel in the tundish when the slab that passed the product was cast. The relationship between the soot amount and the overheating temperature is shown by Δ in FIG.
From FIG. 5, in order to cast a slab that will pass the product, the amount of residual steel in the waiting tundish should be 0.2 tons or less, and the overheating temperature of the molten steel supplied to the tundish It is understood that it is necessary to set the temperature to 45 ° C. (the amount of remaining steel is 0.1 ton) to 53 ° C. (the amount of remaining steel is 0.2 ton).

On the other hand, the tundish 10 provided with the lower weir 20 provided with the through-hole 21 is used, and the amount of remaining steel in the tundish 10 is set to less than 0.6 tons, and molten steels with various overheating temperatures are used. After the molten steel of 10 to 30 tons was supplied into the tundish 10 and casting was started, a slab was manufactured (hereinafter referred to as case 2). FIG. 5 shows the relationship between the amount of remaining steel in the tundish and the overheating temperature on the quality of the product produced from the slab obtained at this time. In FIG. 5, the relationship between the amount of steel remaining in the tundish and the overheating temperature when a slab that passes the product is marked with a circle, and the inside of the tundish when the slab that fails the product is cast. The relationship between the amount of steel remaining and the overheating temperature is indicated by ■.

From FIG. 5, the amount of residual steel in the tundish 10 is set to less than 0.6 tons, the overheating temperature of the molten steel supplied to the tundish 10 is set to a range of 10 to 60 ° C., and the overheating temperature of the molten steel is set to the remaining steel. It can be seen that a slab that can pass the product can be cast by raising the amount as the amount of dredging increases. However, it can be seen that when the increase in the overheating temperature of the molten steel accompanying the increase in the amount of residual steel is small, a slab that is rejected by the product is cast. Further, in case 2, the condition for casting a slab that passes the product, that is, the condition indicated by a circle, is in a wider range than the condition indicated by a triangle that allows a slab that passes the product in case 1 to be obtained. It was found to be distributed.
Therefore, by raising the overheating temperature of the molten steel supplied to the tundish 10 as the amount of remaining steel is increased, and starting casting after 10 to 30 tons of molten steel is held in the tundish 10, It was confirmed that the continuous casting conditions for casting a slab that passed the product could be expanded.

Further, the first and second obtained when the molten steel having an overheating temperature of 10 to 60 ° C. is supplied into the tundish 10 and casting is started after 10 to 30 tons of molten steel is held in the tundish 10. The product was manufactured using the 2nd slab, and the rejection rate of the product at that time was calculated | required. The result is shown in FIG. Moreover, the failure rate which generate | occur | produced in the product manufactured from the 1st and 2nd slab obtained by casting with the conventional continuous casting method of the molten stainless steel which replaces a tundish every time continuous casting is completed is shown in FIG. Shown in In addition, in FIG. 6, the rejection rate is displayed with the index | index based on the rejection rate which generate | occur | produced in the product manufactured from the 1st slab cast with the conventional continuous casting method of stainless steel molten steel.

As can be seen from FIG. 6, the failure rate index generated in the product manufactured from the second slab cast by the conventional continuous casting method of molten stainless steel was 0.77. On the other hand, the failure rate index generated in the product manufactured from the first slab cast by the continuous casting method of the molten stainless steel of the present invention in which the tundish 10 used in continuous casting is continuously used repeatedly is 0.45, The failure index generated in the product produced from the second slab was 0.63.
Therefore, the failure rate index generated in the product manufactured from the slab casted by the continuous casting method of the molten stainless steel according to the present invention is not generated in the product manufactured from the slab casted by the conventional continuous casting method of molten stainless steel. Even if the tundish 10 used in continuous casting is used repeatedly and continuously, it is found that the quality is equivalent to or lower than the acceptance rate index. It was confirmed that the product was obtained.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, The change in the range which does not change the summary of invention is possible, Each above-mentioned embodiment is possible. The case where the continuous casting method of molten stainless steel using the hot reuse tundish of the present invention is configured by combining some or all of the forms and modifications is also included in the scope of the present invention.
For example, in the present embodiment, a stopper formed of a refractory material is used, but an iron stopper that is air-cooled by circulating air inside can be used. By using an iron stopper, it is possible to reliably eliminate the head drop. Moreover, by stopping the air cooling, the stopper can be dissolved in the molten steel by the heat from the molten steel, and natural opening can be performed.
Also, through holes were formed on both sides of the lower end of the lower weir, and trapezoidal discharge guide blocks were placed, but by selecting the shape of the discharge guide block appropriately, it was formed at the lower end of the lower weir The position of the through hole to be changed can be changed, and the number of the through holes can be set to 1 or 3 or more.

It is a sectional side view of the tundish applied to the continuous casting method of the molten stainless steel using the hot reuse tundish which concerns on one embodiment of this invention. It is explanatory drawing of the lower weir arrange | positioned in the bottom part of the tundish and the guide block for evacuation. It is explanatory drawing of the seal lid installed in the opening part of the tundish cover of the tundish. It is explanatory drawing of the sealing material with which it filled between the molten steel discharge hole and stopper of the same tundish. It is a graph which shows the relationship between the amount of steel remaining in a tundish, and overheating temperature. It is a graph which shows the failure generation | occurrence | production in the product manufactured from the 1st and 2nd slab manufactured in the continuous casting.

Explanation of symbols

10: tundish, 11: boat-shaped iron skin, 12: refractory layer for insole, 13: refractory layer for inner wall, 14: overflow hole, 15: stopper, 16: molten steel discharge hole, 17: upper nozzle, 18 : Sliding nozzle, 19: Long nozzle, 20: Lower weir, 21: Through hole, 22: Guide block for evacuation, 23: Side end surface, 24: Upper weir, 25: Tundish cover, 26: Iron skin, 27: Refractory layer for walls, 28: Opening for long nozzle, 29: Opening for stopper, 30: Stopping member, 32: Chain, 33: Seal lid, 35: Whisker layer

Claims (4)

After the end of continuous casting, the tundish is tilted from the horizontal state after the sealing lid is installed at the opening of the tundish cover, and the amount of residual steel in the tundish is 0.1 to less than 0.6 ton After discharging the molten steel and slag until reaching the range, returning the tundish horizontally and waiting in a hot state; and
Supplying molten steel into the tank in the dish waiting, after holding the molten steel in a predetermined amount in the tundish, possess a step of starting pouring into the mold from the tundish,
A lower weir having a through-hole formed in the thickness direction at the bottom of the tundish, and a guide block for evacuation for guiding the molten steel and slag blocked by the lower weir when the tundish is tilted to the through-hole And a continuous casting method of molten stainless steel using a hot reuse tundish. 2. The method for continuously casting molten stainless steel using a hot reuse tundish according to claim 1, wherein the predetermined amount of molten steel held in the tundish is 10 to 30 tons. Continuous casting method of molten stainless steel using hot reuse tundish. In the continuous casting method of the stainless molten steel using the hot reuse tundish according to any one of claims 1 and 2, the overheating temperature of the molten steel supplied to the waiting tundish is 10 ° C or more. A continuous casting method for molten stainless steel using a hot reuse tundish, characterized in that the temperature is 60 ° C. or less and the overheating temperature is increased with an increase in the amount of residual steel in the tundish. In the continuous casting method of the molten stainless steel using the hot reuse tundish according to any one of claims 1 to 3 , a stopper is inserted into the molten steel discharge hole of the waiting tundish, and the molten steel A continuous casting method of molten stainless steel using a hot reuse tundish, wherein a sealing material is filled between the discharge hole and the stopper.

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