JP5885339B2 - How to use the stopper for molten steel - Google Patents

Description

The present invention relates to the use of molten steel stopper over, in particular, once it relates reuse can become such novel improvements of the shape of the stopper rod of the stopper used.

The stopper for opening and closing the outlet of this type of molten steel container that has been used conventionally is generally composed of an elongated cylindrical refractory made of alumina graphite formed by isostatic pressing, and the aforementioned elongated cylindrical refractory. The body has a round or tapered shape (stopper head) at the lower end suitable for coupling to the throat of the corresponding outlet nozzle. Moreover, it has a mechanism which raises / lowers the said stopper outside, and a molten steel flow volume is controlled by it.
In the case of tundish for continuous casting, a stopper is installed to prevent slag from getting caught at the end of casting. When using the stopper in the tundish, it is connected to the vertical mechanism of the stopper through a small hole opened in the tundish lid installed for heat insulation of the molten steel.

That is, FIG.4 and FIG.5 has shown the use condition of the stopper 1 provided in the molten steel container 20 which consists of a conventional tundish, for example.
The molten steel container 20 includes a tundish iron skin 10 and a tundish lid 8, and a tundish main body refractory 11 is lined on the inner side of the tundish iron skin 10, and an outlet 12 a is provided at the bottom thereof. A nozzle 12 is provided.

A small hole 7 is provided in the tundish lid 8, and a stopper 1 is disposed in the molten steel container 20, and a vertical mechanism 21 (not shown) chucks the attachment portion 9 of the stopper 1 to stop the stopper 1. It can be moved up and down.
When the stopper head 2 of the stopper 1 contacts the outlet 12a of the nozzle 12, the outlet 12a is closed, and the discharge of the molten steel 5 from the outlet 12a of the nozzle 12 is stopped.

Next, a specific method of using the stopper 1 is as follows. That is, the stopper 1 is installed at the closed position of the nozzle 12 at the start of casting. In this state, the molten steel 5 is supplied into the molten steel container 20 from an unillustrated molten steel ladle through an air seal pipe or the like. The stopper 1 moves to the upper release position in a state where the molten steel 5 has accumulated more than a certain level of depth. During continuous casting, the stopper 1 is fixed at the release position, and the flow rate control of the molten steel 5 is performed by a well-known sliding plate separately provided below. Since the molten steel head is preferably constant for flow rate adjustment, the molten steel head is kept constant by a sliding nozzle installed in the ladle during casting. Although a molten steel head changes with kinds of the molten steel container 20, it is about 400 mm-2000 mm. At the end of casting, the supply of molten steel from the ladle stops, so the molten steel level decreases with time. When the molten steel head reaches a certain value (several tens to 100 mm), the stopper 1 is moved from the release position to the closed position, and the outflow of the molten steel 5 from the outlet 12a is stopped. The purpose of this stop is to prevent the outflow from swirling near the outlet 12a and entraining the molten slag 4 floating on the molten steel 5.
Further, while the molten steel head is kept at a constant level during casting, the molten slag 4 mixed in the molten steel 5 floats, and a slag layer having a thickness of several tens of mm is formed on the molten steel 5 in the molten steel container 20. It is formed. The position of this slag layer is referred to as slag line 4a (shown in FIG. 2).
In addition, in the case of the stopper rod of Patent Document 1, as shown in FIG. 2C and FIG. 3B, the intermediate portion of the stopper rod 3 positioned on the slag line 4a has an upper side and a lower side. A narrow diameter portion 27 is formed through each tapered portion 25, 26, and a configuration is proposed in which the narrow diameter portion 27 reduces the formation of a cocoon-like slag solidified product.

Japanese Patent No. 4,777,611

Since the conventional stopper is configured as described above, the following problems exist.
That is, conventionally, the above-described stopper cannot be completely removed from the solidified slag 6 adhering to the stopper, and therefore, after being used once, it is discarded without being reused.
On the other hand, attempts are being made to reuse stoppers that have been used once from the viewpoint of resource saving and cost saving.
For this reuse, it was necessary to check whether it could withstand the reuse, and some repairs were necessary if necessary. The problem will be described with reference to FIGS. First, for inspection, it is necessary to pull out the stopper 1 inserted into the molten steel container 20 through the small hole 7 of the tundish lid 8, but a bowl-like slag solidified product 6 is formed on the top of the stopper 1. When the diameter of the lid 8 is larger than the diameter of the small hole 7 of the lid 8 and cannot be pulled out, or when it is forcibly pulled out, there is a problem that the stopper rod portion 3 is broken.
If it is discarded after a single use, there is no problem even if the slag solidified product 6 is generated or the stopper 1 is broken for pulling out, but it is a problem caused by reuse. Yes, it does not exist as a prior art so far.
Therefore, as a countermeasure against the trial, the diameter of the intermediate portion of the stopper rod 3 of the slag line 4a is reduced to a small diameter (shown in FIG. An attempt was made to reduce slag solidified product 6 but it was not improved.

Therefore, the present inventors have observed the adhesion state of the cocoon-like slag solidified product 6 in an actual machine, and have come up with the present invention after considering a countermeasure based on the observation.
That is, the diameter of the stopper rod portion 3 is 80 to 200 mm, and the small hole 7 of the lid 8 is provided with a gap of 100 to 250 mm from the stopper rod 3. The reason for forming the gap is a margin for preventing interference when the stopper 1 is installed and operated, and also serves as an observation hole for observing the state in the molten steel container 20 from the gap.
The solidified slag 6 formed in the above-described bowl shape slightly changes depending on operating conditions, but generally has a thickness of about 10 to 50 mm and a diameter of about 600 to 1000 mm. The slag-like solidified product 6 is produced by cooling and solidifying the molten slag floating on the molten steel 5, and the following two points are considered as the cooling mechanism.
The first is heat radiation by radiation from the gap between the small hole 7 and the stopper 1. The diameter of the small hole 7 of the lid 8 is determined, and if it is to be changed, a large equipment cost is required, it is difficult to change the conditions, and it is difficult to suppress the amount of heat released by radiation. The other is heat transfer. Since the stopper 1 is made of alumina / graphite, the heat conductivity is relatively high, and heat is transferred and released through the stopper rod 3. Again, it is difficult to change the material. In other words, it is difficult to suppress the formation of the cocoon-like slag solidified product 6.

Therefore, it was examined whether the solidified slag 6 could be easily broken or dropped during the movement of the stopper 1.
Although the method of using the stopper 1 has already been described, it is as follows when only the movement of the stopper 1 in the vertical direction is arranged in stages. (1) Install the lid 8 and the stopper 1 at the molten steel container maintenance site. (2) At the start of continuous casting, the stopper 1 is lowered (the outlet 12a is closed). (3) The molten steel 5 is caused to flow into the molten steel container 20 from the ladle. When the molten steel 5 accumulates in the molten steel container 20 and reaches the reference value, the stopper 1 is raised to the upper standby position (the outlet 12a is in an open state). (4) Usually, hold as it is until the end of continuous casting. (5) When the continuous casting is finished, the stopper 1 is lowered when the molten metal surface is lowered to a specified value. (6) After the continuous casting is finished, the molten steel container 20 is moved to the maintenance shop, and the stopper 1 is pulled out.

The above-mentioned cocoon-like slag solidified product 6 is formed during the above-mentioned (4). On the other hand, it is the stage (6) that has a problem in pulling out. Therefore, it was thought that it should be destroyed and dropped at the stage (5).
In the stage (4), the formed slag solidified product 6 is on the molten steel 5 and receives buoyancy from the molten steel 5. On the other hand, the molten steel head in the stage (5) is several hundred mm below the stage (4). In this state, the cocoon-like slag solidified product 6 is in the air and there is no buoyancy of the molten steel 5, and is in a state supported by the strength of the adhesion surface with the stopper rod portion 3 and the strength of the slag solidified product 6.
On the other hand, when the stopper 1 moves downward by the movement of (5) and closes the outlet 12a of the nozzle 12, the stopper 1 has a speed of about several tens of mm / second and stops against the nozzle 12. It was considered that the slag solidified product 6 can be destroyed and dropped by using the impact at this time.

First, the first method is to break down the slag solidified product 6 by reducing the diameter of the stopper rod 3 and reducing the adhesion area between the slag solidified product 6 and the stopper rod 3 as in the configuration of Patent Document 1. Tried to drop out. However, the cocoon-like slag solidified product 6 only moved slightly downward and did not break or fall off.
Therefore, in order to make it easy to break, it is considered that a tapered portion 25 such as a wedge should be formed, and the stopper rod 3 of the stopper 1 is used with the first tapered portion 25 having a small diameter that becomes smaller on the upper side. As a result of an experiment on an actual machine, when the slag solidified product 6 tries to come out downward through the second tapered portion 26 due to an impact when the stopper 1 hits the nozzle 12 and stops, the inside of the slag solidified product 6 The hole 6a was destroyed by the increase in the outer diameter of the tapered portion 26, the slag solidified product 6 was broken and dropped, the bowl-shaped slag solidified product 6 disappeared, and the reuse rate of the nozzle 12 was improved.

Using molten steel stopper chromatography according to the present invention, which has a mounting portion for connection to the elevator mechanism at the top, have a substantially circular horizontal cross-section, the outflow and the molten steel from the outlet of the nozzle of the molten steel container In a method of using a stopper for molten steel that uses a stopper having a stopper rod portion having a stopper head for closing, a tapered portion having a shape whose diameter is reduced on the upper side in a longitudinal section passing through the axial center of the stopper rod portion. The position in the height direction formed by the molten steel slag floating on the molten steel when the stopper head is in the release position with respect to the outlet is defined as a slag line, and the tapered portion is positioned in the slag line. or, a portion thereof is disposed so as to be located within 50mm from the slag line, the nozzles in the stopper A shock by the method of slag solidified product Ru to break falling when closing the outlet, The angle of the tapered portion is a method which is 20 degrees 1 degree.

Using molten steel stopper chromatography according to the present invention, since it is constructed as described above, it is possible to obtain the following effects.
That is, a stopper having a mounting portion for connecting to an up-and-down mechanism at the top, a stopper having a substantially circular horizontal cross section, and a stopper head for flowing out and closing the molten steel from the nozzle outlet of the molten steel container In the method of using a stopper for molten steel using a stopper provided with a rod portion, the stopper rod portion is provided with a tapered portion having a shape whose diameter becomes smaller on the upper side in a longitudinal section passing through the axial center thereof, and the stopper is provided with respect to the outlet. The position in the height direction formed by the molten steel slag that floats on the molten steel when the head is in the release position is defined as a slag line, and the tapered portion is positioned in the slag line, or a part thereof is the slag line. placed so as to be positioned within more 50 mm, the impact when closing the outlet of the nozzle by the stopper Order to break shed lug solidified product, collar-shaped slag solidified product formed in use, by the impact when abutted by dropping the stopper to the nozzle, the shape whose diameter expands downward taper The action spread by the part works, it is easily destroyed, and the stopper can be reused.
When the angle of the tapered portion is 1 degree to 20 degrees, the destructive action of the slag solidified product can be obtained with high efficiency.

It is a block diagram which shows the stopper in the usage method of the stopper by this invention. (A) is a block diagram showing another embodiment of the stopper according to the present invention, in which the tapered portion is located within 50 mm from the lower surface of the slag line. (C) is a block diagram when the stopper of patent document 1 is applied to this invention. (A) is a block diagram showing a conventional stopper in FIGS. 4 and 5, (b) is a block diagram showing a stopper of Patent Document 1, and (c) is a comparative example of the present invention with a taper angle outside the present invention. A block diagram and (d) are block diagrams of the stopper which a diameter becomes small toward the lower side by the comparative example of this invention. It is the cross-sectional schematic which shows the stopper in the conventional molten steel container. It is a cross-sectional schematic diagram which shows the state which pulls out the stopper after molten steel discharge in the conventional molten steel container.

An object of this invention is to provide the usage method of the stopper which has the shape of a stopper rod so that the stopper once used can be reused.

Hereinafter, a preferred embodiment of the use of molten steel stopper chromatography according to the present invention will be described with reference to the accompanying drawings.
The same or equivalent parts as those in the conventional example will be described with the same reference numerals, and the configurations shown in FIGS. 2 to 5 will also be used to explain the stopper of the present invention.
FIG. 1 is a block diagram showing a stopper 1 according to the present invention.
In FIG. 1, what is indicated by reference numeral 1 is a stopper 1 having a substantially circular horizontal cross section. An upper portion of the stopper 1 is moved up and down in a molten steel container 20 such as a tundish. A mounting portion 9 for chucking is formed by a well-known vertical mechanism 21 used for the above.

A portion different from the conventional configuration of the stopper 1 is provided with a tapered portion 26 configured to form a small-diameter portion 30 whose diameter is narrowed on the upper side in a longitudinal section passing through the axial center thereof. By positioning the taper portion 26 on the slag line 4a made of the molten steel slag 4, or by positioning a part thereof within 50 mm from the slag line 4a, the slag solidified product 6 can be destroyed as described later. It is configured as follows.
In the case of the configuration of the stopper 1, portions other than the tapered portion 26 are the same as those of the conventional stopper 1, and thus the same reference numerals are given and description thereof is omitted.

  In the movement of the stopper 1 of FIG. 4 and FIG. 5 in the molten steel container 20, the molten steel head is located to some extent below the slag line 4 a when moving to the closing position for closing the outlet 12 a of the nozzle 12. The cage-like slag solidified product 6 is in a floating state as shown in FIG. And is held by. Although the slag solidified material 6 obtains kinetic energy by the downward movement of the stopper 1, the stopper head 2 collides with the nozzle 12 which is the molten steel outlet and stops at the closed position. The slag solidified product 6 exerts a downward force due to the inertial energy due to the impact. At this time, the taper portion 26 having an axial length A that is slender at the slag line 4a is provided, so that the destruction / dropout is likely to occur. That is, it is considered that the destruction / drop-off mechanism is that the crack of the inner hole 6a spreads due to the wedge effect of the tapered portion 26, and the solidified slag 6 breaks and falls off. For example, when the tapered portion 26 is not provided, even if some cracks are generated, the cocoon-like slag solidified product 6 is only slightly shifted downward, and does not fall off. However, if the tapered portion 26 is located immediately below after being shifted downward, the same wedge effect is exhibited. For this reason, if the position of the taper part 26 is within 50 mm below the slag line 4a (shown in FIG. 2a), the wedge effect can be exhibited to some extent. More preferably, it is located at the tapered portion 26 (shown in FIGS. 1 and 2 b and c).

The angle θ (shown in FIG. 1) of the tapered portion 26 is preferably 1 to 20 degrees. As a result of the experiment, if it is less than 1 degree, the wedge effect is not exhibited, and if it is greater than 20 degrees, the wedge effect is not sufficiently exhibited. More preferably, it was confirmed that 2 to 10 degrees was optimum.
The tapered portion 26 that forms the small-diameter portion 30 whose diameter becomes narrower on the upper side in the longitudinal cross section passing through the axial center 1a does not necessarily have to be a straight line in the cross section. A curve such as a hyperbola may be used. In the case of a curve, the angle of the taper portion 26 indicates a portion where the slag line 4a is located. When the slag line 4a is located immediately above the taper portion 26, the thickness of the slag line 4a from the taper start portion of the taper portion 26 is determined. Refers to the taper at half the position.
The cross-sectional shape above the taper portion 26 is not specified, and may have the same diameter, or may have an inverse taper that widens at the top.

The above-described stopper head 2, the holding mechanism for the stopper portion 26, and the vertical mechanism for the stopper portion 26 do not need to be particularly specified as a mechanism peculiar to the present invention, and well-known general ones can be used. As long as the diameter of the stopper rod portion 3 satisfies the requirements of the present invention, there is no problem even if the diameter at the position of the stopper head 3 and the diameter at the connecting portion of the stopper 1 to the vertical mechanism are different.
In addition, the material has been described by taking alumina / graphite as an example, but not only this but also a material selected from one or more refractory materials selected from alumina, silica, zirconia, chromia, magnesia, and carbon. Applicable to the created stopper. Different materials can be combined.
The manufacturing method is not particularly specified. For example, it can be molded and fired by isostatic pressing. Alternatively, it can be molded by uniaxial press molding and fired.
Further, addition of a metal for preventing oxidation or application of a surface covering material may be performed.

(Comparative Example 1)
A stopper 1 having a conventional configuration was used in a tundish 20 having a capacity of 25 t installed in a continuous casting machine for molten steel. The stopper 1 was inserted into the tundish 20 through a small hole 7 having a diameter of 540 mm opened in the tundish lid 8 with the upper part attached to the vertical mechanism.
The stopper 1 has a diameter of 130 mm and a length of 1200 mm. The diameter of the stopper rod part 3 was made uniform. The slag line 4a was in a standby state during use of the stopper 1, that is, the position of the slag line 4a in the above-described continuous casting stage was located at a position 600 mm from the tip of the stopper 1. The material of the stopper 1 was alumina / graphite used in isostatic pressing.
The molten steel was received from a ladle having a capacity of 230 t and continuously cast with a number of 4-7. When the stopper 1 was tried to be pulled out for maintenance of the tundish 20 after completion of casting, a bowl-like slag solidified product 6 was generated, and the stopper 1 was often broken without being pulled out. The recovery rate was only 16%. The diameter of the cocoon-like slag solidified product 6 was approximately 500 to 800 mm.

(Comparative Example 2)
In the same tundish 20 as in Comparative Example 1, the stopper 1 of Patent Document 1 was used. A tapered portion 26 is provided so that the diameter at the 250 mm position decreases from 130 mm to 110 mm at the position of 250 mm to 350 mm from the tip of the stopper 1, and 750 mm at the position of 750 mm to 850 mm from the tip of the stopper 1. A tapered portion 26 is provided so that the diameter of the position increases from 110 mm to 130 mm at the 850 mm position. The material was the same as in Comparative Example 1.
As in Comparative Example 1, molten steel was received from a molten steel ladle having a capacity of 230 t and continuously cast with a number of 4-7. When the stopper 1 was tried to be pulled out for maintenance of the tundish after completion of casting, a bowl-like slag solidified product 6 was generated, and the stopper was often broken without being pulled out. The recovery rate was only 20%. When observed, deviation from the rod portion of the cocoon-like slag solidified product 6 was observed. As described above, the stopper 1 of Patent Document 1 cannot be significantly improved.

Experimental Example In the same tundish 20 as in Comparative Examples 1 and 2, the stopper according to the present invention was used. A taper portion was provided such that the diameter at the 500 mm position decreased from 130 mm to 120 mm at the 650 mm position at a position from 500 mm to 650 mm from the tip of the stopper. The materials were 1, 2 and the same as the comparative example.
As in the comparative example, molten steel was received from a ladle having a capacity of 230 t and continuously cast with a number of 4 to 7. When the stopper 1 is pulled out for maintenance of the tundish after completion of casting, the slag line 4a is located in the small diameter portion 30 of the tapered portion 26, and the slag solidified material 6 is formed in the small diameter portion 30. When the stopper 1 was pulled upward, the solidified slag 6 was broken at the end of the tapered portion 26, so that it was easily pulled out in any case, and the recovery rate was improved to 100%. It was observed that the cocoon-like slag solidified product 6 was only slightly left in the bonded portion with the stopper rod portion 3 and cracked and dropped off. Thus, the superiority of the rod according to the present invention is clear.
Accordingly, in the stopper 1 used through the small hole 7 opened in the heat retaining lid 8 of the molten steel container 20, it becomes possible to easily remove the slag-like solidified slag 6 formed during use. It can be reused.

  2A, 2B, and 2C show other forms of the stopper 1 according to the present invention. FIG. 2A shows the configuration of the present invention, and the axial length A of the tapered portion 26 is a slag line. (B) is another embodiment of the present invention, in which the positional relationship between the angle θ of the tapered portion 26 and the slag line 4a is changed (the tapered portion 26 becomes the slag line 4a). (C) is a form in which the stopper 1 of Patent Document 1 is applied to the positional relationship of the slag line 4a of the present invention and has first and second tapered portions 25 and 26, and (b) , (C) can break and remove the solidified slag 6 as in (a) of the present invention.

Here, in order to demonstrate how the stopper 1 of the present invention can easily remove the solidified slag 6 and is superior to the conventional example, a comparative explanation will be given using the configuration of FIG.
(A), (b), (c), (d) of FIG. 3 is a form which shows the comparative example of the stopper 1 of this invention.
(A) is the stopper 1 of the conventional structure shown in FIG.4, FIG.5, (b) is a structure of the stopper 1 in the case of patent document 1, (c) is similar to the stopper 1 of this invention. In the configuration, the angle of the tapered portion 26 is different from that of the present invention, and the axial length A is also shorter than that of the present invention. (D) shows that the slag line 4a of the molten steel slag 4 is different from the present invention. The first tapered portion 25 and the second tapered portion 26 having opposite shapes, the first tapered portion having the axial length A ′ has a smaller diameter on the lower side, and the second tapered portion 26 has a taper direction in the direction of the taper. The configuration is the same as that of the present invention, but the axial length A and the taper angle are different.
Therefore, in the configuration of the stoppers 1 described above (a) to (d), it is impossible to destroy the bowl-shaped slag solidified product 6 just by causing the stopper 1 to collide with the nozzle 12.

Here, summarized the gist of the use of soluble steel stopper over in accordance with the present invention is as follows.
A stopper for connecting and discharging the molten steel 5 from the outlet 12a of the nozzle 12 of the molten steel container 20 and having a substantially circular horizontal cross section while having an attachment portion 9 for connecting to the vertical mechanism 21 at the top. In the method of using the stopper for molten steel using the stopper 1 having the stopper rod portion 3 having the head 2, the stopper rod portion 3 is provided with a tapered portion 26 having a shape whose diameter becomes smaller on the upper side in a longitudinal section passing through the axial center thereof. The position in the height direction formed by the molten steel slag 4 floating on the molten steel 5 when the stopper head 2 is in the release position with respect to the outlet 12a is defined as a slag line 4a, and the tapered portion 26 is Situated in the slag line 4a, or placed as a part thereof located within 50mm from the slag line 4a, before Methods of use to destroy dropping slag solidified product 6 by the impact when closing the outlet 12a of the nozzle 12 with a stopper 1, also the angle of the tapered portion 26, how to use the once Ru 20 degrees der It is.

Using molten steel stopper chromatography according to the present invention, it is possible to remove the slag solidified matter adhered to the stopper after use by simply colliding stopper to the nozzle, can be easily realized reuse of the stopper.

DESCRIPTION OF SYMBOLS 1 Stopper 1a Shaft center 2 Stopper head 3 Stopper rod part 4 Molten steel slag 4a Slag line 5 Molten steel 6 Slag solidified material 7 Small hole 8 Tundish lid 9 Attachment part 10 Tundish iron skin 11 Tundish body refractory 12 Nozzle 12a Outlet 20 Molten steel container (tundish)
21 Vertical mechanism 26 Tapered portion 27 Small diameter portion 30 Small diameter portion 41 Solidified molten slag 51 Solidified steel A Axial length θ Taper angle

Claims (2)

The upper part has a mounting part (9) for connection to the vertical mechanism (21), and has a substantially circular horizontal cross section, and the molten steel from the outlet (12a) of the nozzle (12) of the molten steel container (20) In the method of using the stopper for molten steel using the stopper (1) provided with the stopper rod part (3) having the stopper head (2) for performing the outflow and blockage of (5),
The stopper rod portion (3) is provided with a tapered portion (26) having a shape whose diameter decreases on the upper side in a longitudinal section passing through the axial center thereof, and the stopper head (2) is in a release position with respect to the outlet (12a). The position in the height direction formed by the molten steel slag (4) floating on the molten steel (5) in the case of the slag line (4a),
The taper part (26) is positioned so as to be located in the slag line (4a) or a part thereof is located within 50 mm from the slag line (4a ), and the nozzle ( using molten steel for a stopper, characterized in Rukoto to break falling slag solidified product (6) by the impact when closing the outlet (12a) of the 12). Angle of the tapered portion (26), the use of molten steel for a stopper according to claim 1, wherein the 1 degree is 20 degrees.

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