JP2011245491A - Device and method for pouring molten steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for pouring molten steel, capable of rapidly preventing pouring of molten steel containing filler sand into a tundish.SOLUTION: The device configured to safely and easily prevent, in the pouring stage of the molten steel 10 to the tundish 6, inclusion of filler sand to the tundish 6 includes: a sliding nozzle 2 having a pouring opening 2a for pouring the molten steel from a ladle 1 to the tundish. The sliding nozzle has a second opening 2b different from the pouring opening, and the second opening is allowed to communicate with a filler sand receiver 3 through a filler sand discharge nozzle 4. The filler sand discharge nozzle is slidable relative to the filler sand receiver.

Description

  The present invention relates to a pouring technique for pouring molten steel into a tundish provided at a ladle outlet used in a continuous casting apparatus, and in particular, to improve the cleanliness of steel such as bearing steel and case-hardened steel. The present invention relates to a pouring technique suitable for the above.

  In steels that require a high fatigue life, such as steels such as bearing steel and case hardening steel, it is essential to reduce non-metallic inclusions in the steel that degrade the fatigue life. The non-metallic inclusions are mixed or generated in the steelmaking stage, but have been reduced by various efforts.

  However, although the number of inclusions present in the molten steel at the end of degassing is controlled to be less than or equal to a predetermined value, the number of inclusions in steel greatly increases when entering the tundish. was there. As a result of detailed investigations by the inventors, it has been found that this cause is caused by packed sand packed in the steel outlet of the pan. Packing sand has the role of molten steel dredge, and when the sliding nozzle is poured to pour into the tundish from the ladle, the filling sand falls into the tundish with the molten steel. To do. Most of the packed sand that has entered the tundish floats in the tundish and is absorbed by the tundish slag, so it should not enter the product, but some packed sand may be mixed into the product. There is.

  Among the mixed sand, the one mixed into the product becomes non-metallic inclusions, and the non-metallic inclusions may remain in the parts even after the steel is processed into parts such as bearings. In particular, when there are large non-metallic inclusions exceeding 20 μm, for example, on the rolling surface of the bearing (the surface that receives a load in contact with a rolling element such as a roller), the non-metallic inclusions are the starting point of fatigue. As a result, the life of the parts is reduced.

As a technique for preventing mixed sand from being mixed into the molten steel injected into the tundish, there are techniques as disclosed in Patent Documents 1 to 3, for example.
In Patent Document 1, when pouring molten steel into a tundish from a ladle having a sliding nozzle, the sliding nozzle is opened in advance in a state in which a hot water pot is arranged in the tundish, and a long nozzle is inserted. The molten steel containing the stuffed sand that has fallen is received in the hot water pot. Thereafter, the sliding nozzle is once closed to stop pouring. And after removing the said hot water pot which received the molten steel containing filling sand from a tundish, a sliding nozzle is opened again and the pouring of the hot water in a tundish is restarted. This prevents the filling sand from entering the tundish.

  Moreover, in the technique described in Patent Document 2, a water-cooled mold that is opened up and down is installed in the middle of the movement path to the pouring position of the ladle, and the lower part of the water-cooled mold is closed with a dummy block. Then, once the sliding nozzle is opened at the position where the water-cooled mold is installed, the molten steel containing packed sand filled in the ladle outlet is discharged toward the water-cooled mold, and then the ladle is moved to the casting position. Casting. Thereby, mixing of the filling sand into the molten steel is suppressed at the time of casting.

  Moreover, in the technique of patent document 3, in order to suppress obstruction | occlusion of the steel outlet of a ladle, the technique which blows away only packed sand to the side and removes it by blowing gas from the sliding nozzle exit vicinity side. Has been proposed.

JP 2007-326116 A Japanese Patent Laid-Open No. 5-200534 Japanese Patent No. 3388661

  However, the technique described in Patent Document 1 requires at least a step of installing a hot water pot in the tundish and a step of lifting and removing the hot water pot that has received molten steel containing packed sand from the tundish. Therefore, it takes time. Moreover, since the sliding nozzle is in contact with the molten steel while the hot water pot that has received the molten steel containing the packed sand is being removed, there is a risk that the molten steel will solidify and block the steel outlet.

Also, in the technique described in Patent Document 2, since the ladle movement is stopped in the middle and the filling sand packed in the steel outlet is discharged, the molten steel is removed when it takes time to move the ladle. It may solidify and block the steel outlet.
Further, in the technique disclosed in Patent Document 3, it is necessary to attach a suction collection device to the receiving side so that molten steel does not scatter when the packed sand is blown away. In addition, when pouring from a ladle, it is possible to cast with a short nozzle, but in order to melt the high clean steel targeted by the present invention, a nozzle is used in the tundish using a long nozzle. This is presumed to be difficult, for example, when casting is started after inserting and replacing with argon.

  The present invention has been made paying attention to the above points, and shortens the time from removal of clogged sand to pouring of tundish, and pouring molten steel containing clogged sand into tundish. The purpose of this technology is to pour molten steel.

In order to solve the above-mentioned problems, the present invention makes it possible to safely and easily remove the inclusion of packed sand in the tundish at the stage of pouring molten steel into the tundish.
That is, the invention described in claim 1 is provided with a sliding nozzle having a pouring opening for pouring molten steel from the ladle to the tundish, and the sliding nozzle is a second one separately from the pouring opening. An apparatus for pouring molten steel is provided, characterized in that the second opening is communicated with a packed sand receiver.

  Next, the invention described in claim 2 includes a packed-sand discharging nozzle that communicates the second opening and the packed-sand receiver, and the packed-sand discharging nozzle extends along the sliding direction of the sliding nozzle. It is characterized in that it is connected to the packed sand receiver in a state where it can move relative to the direction.

  Next, the invention described in claim 3 is provided with the pouring device according to claim 1 or 2, and once sliding so that the second opening communicates with the tap outlet of the ladle at the start of pouring. After the nozzle is slid and molten steel containing packed sand is received by the packed sand receiver through the second opening, the opening for pouring of the slide nozzle is communicated with the steel outlet of the pan and molten steel is supplied to the tundish. The present invention provides a method for pouring molten steel characterized by pouring hot metal.

  According to the present invention, the sliding nozzle is provided with a second opening for discharging packed sand separately from the pouring opening, and the second opening is communicated with the packed sand receiver. By simply sliding the sliding nozzle and switching, it is possible to switch in a short time from the discharge of the molten metal containing packed sand at the initial stage of pouring until the start of pouring to the subsequent tundish.

As a result, no extra time is required for pouring hot water for discharging packed sand, and the molten steel can be poured safely by removing the filled sand and preventing the mixed sand from entering the tundish.
According to the invention of claim 2, even if the sliding nozzle is slid, it is not necessary to move the packed sand receiver.

It is a figure which shows the installation which performs the pouring to the tundish from the ladle which concerns on embodiment based on this invention. It is a key map showing a pouring device concerning an embodiment based on the present invention. It is a perspective view which shows the packed sand receiver which concerns on embodiment based on this invention.

Next, embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing equipment for pouring hot water from a ladle into a tundish.

(Equipment configuration)
As shown in FIG. 1, a sliding nozzle 2 is attached to the steel outlet 1 a of the ladle 1. As shown in FIG. 2, the sliding nozzle 2 is formed with an opening 2a for pouring hot water and a second opening 2b for discharging packed sand. One end of a long nozzle 5 is connected to the opening 2a for pouring. In addition, one end of a nozzle 4 for discharging packed sand is connected to the second opening 2b. Reference numeral 7 denotes a nozzle fixing jig 7 for fixing the long nozzle 5 and the filling sand discharging nozzle 4 to the sliding nozzle 2. As a result, the long nozzle 5 and the filling sand discharging nozzle 4 can be slid together with the sliding nozzle 2.

The other end of the packed sand discharge nozzle 4 is connected to the packed sand receiver 3. Accordingly, the second opening 2b communicates with the packed sand receiver 3 through the packed sand discharge nozzle 4.
Here, the other end portion of the packed sand discharging nozzle 4 is connected to the packed sand receiver 3 in a relatively slidable state. That is, even if the sliding nozzle is slid, it is not necessary to provide a mechanism for moving the packed sand receiver 3. The sliding direction is a direction along the sliding direction of the sliding nozzle.

The packed sand receiver 3 is, for example, a rectangular container having an open upper side, and a through hole 3a into which a nozzle can be loosely inserted is opened at an upper portion of the side wall. The nozzle for discharging the packed sand is inserted into the through hole 3a. The other end portion of 4 is inserted so that the tip portion protrudes into the packed sand receiver 3. As a result, the other end portion of the nozzle 4 for discharging the packed sand is relatively slidable.
The packed sand receiver 3 of this embodiment is detachably attached to the bottom surface of the ladle 1.

(Example of use)
When the ladle 1 containing the molten steel 10 is moved to above the tundish 6 and poured into the tundish 6, the sliding nozzle 2 is slid in the direction a in FIG. The second opening 2 b is communicated with the mouth 1 a, and the molten steel 10 containing packed sand is discharged to the packed sand receiver 3 through the packed sand discharging nozzle 4.

When the discharging time during which the packed sand can be completely removed has elapsed, the sliding nozzle 2 is slid in the direction b in FIG. Start pouring to 6.
Here, the said discharge | emission time is determined by calculating | requiring the time which can discharge | emit completely without throwing away the molten steel 10 wastefully by experiment.

The molten steel 10 containing packed sand discharged to the packed sand receiver 3 is removed from the packed sand receiver 3 by removing the packed sand receiver 3 after moving the ladle 1 from the tundish 6 after pouring is completed.
Here, although the case where the packed sand receiver 3 is detachably attached to the pan 1 is illustrated in the above embodiment, the packed sand receiver 3 may be detachably attached to the tundish 6 side.
In this case, for example, as shown in FIG. 3, a recess 3b on which the nozzle can be slidably mounted may be formed on the upper surface of the packed sand receiver 3.

  As described above, according to the present embodiment, the sliding nozzle 2 is provided with the second opening 2b for discharging the packed sand separately from the pouring opening 2a, and the second opening 2b is provided as the packed sand receiver 3. By adopting a simple configuration of communicating with the slab, the sliding nozzle 2 can be slid and switched to quickly discharge the molten metal containing packed sand in the initial stage of pouring into the tundish 6 in a short time. You can switch. Moreover, it can be carried out at the molten steel pouring stage.

  As a result, no extra time is required for discharging the packed sand, and the molten sand 10 can be poured safely and the molten steel 10 poured into the tundish 6 can be poured.

  For JIS SUJ2 steel, each of a comparative example method of discharging packed sand as it is into the tundish 6 and a method of an example of discharging the packed sand to the packed sand receiver 3 using the pouring device described in the above embodiment. I cast it in. The steel material was rolled to φ60 mm to obtain a product. After macro-etching the C cross-section of these products and clarifying the direction of one surface, 30 samples of 10 mm x 10 mm inclusion observation were taken from the cross-section of one surface D / 4 position L, and the cleanliness was compared by microscopic observation. did.

For the cleanliness, the maximum inclusion diameter of each sample was subjected to extreme statistics, and an inclusion diameter of 30000 mm ² was predicted.
The results are shown in Table 1.

As can be seen from Table 1, it was clearly found that the examples according to the present invention have better cleanliness than the comparative examples.
It was also confirmed that the time required to remove the packed sand in the packed sand receiver 3 did not take much.

  As described above, by adopting the present invention, it can be seen that the packed sand in the pan can be removed quickly and safely before pouring into the tundish 6 and the cleanliness of the product can be improved.

DESCRIPTION OF SYMBOLS 1 Ladle 1a Steel outlet 2 Sliding nozzle 2a Pouring opening 2b 2nd opening 3 Packed sand receptacle 3a Through-hole 3b Recess 4 Packed sand discharge nozzle 5 Long nozzle 6 Tundish 7 Nozzle fixing jig 10 Molten steel

Claims (3)

Equipped with a sliding nozzle with an opening for pouring molten steel from the ladle to the tundish,
The above-mentioned sliding nozzle has a second opening separately from the opening for pouring, and the second opening is communicated with a packed sand receiver.   A packed sand discharge nozzle is provided that communicates the second opening and the packed sand receiver, and the packed sand discharge nozzle is relatively movable in a direction along the sliding direction of the sliding nozzle, and the packed sand is discharged. The molten steel pouring device according to claim 1, wherein the molten steel pouring device is connected to a receiver.   The molten steel containing the filling sand is provided by sliding the sliding nozzle once so that the second opening communicates with the steel outlet of the ladle at the start of pouring. The molten steel is poured into the tundish after the opening for pouring of the slide nozzle is received through the opening of 2 and the opening for pouring of the slide nozzle is communicated with the steel outlet of the pan. Hot water method.

Images