Apparatus for continuous slab casting

The apparatus for continuous slab casting having a nozzle exchanging-holding mechanism capable of moving a submerged nozzle at the exchange of the nozzle through a moving-connecting space D of a base under a slide valve mechanism and keeping the connection between the submerged nozzle and the slide valve mechanism during the operation, and a rotation mechanism to rotate the base of the nozzle exchanging-holding mechanism, which is characterized by a fixing mechanism that fixes the submerged nozzle in the nozzle exchanging-holding mechanism by pressing the submerged nozzle toward one or both inner sides of the moving-connecting space D of the base in one or both directions perpendicular to the moving direction of the submerged nozzle during the nozzle exchange.

TECHNICAL FIELD

The present invention relates to an apparatus for the continuous slab casting and, more specifically, to an apparatus for the continuous slab casting in which the molten metal in a slab mold is rotated and stirred by arbitrarily changing a discharge angle of the molten metal during the casting process.

BACKGROUND ART

In recent years, ingots (referred to also as strands) of steels or various kinds of alloys or the like are mass-produced generally by using a so-called “continuous casting method” which includes the steps of continuously injecting the molten metal in a melting state into a water-cooled mold and gradually drawing out solidified ingots from the mold.

In order to obtain high-quality ingots with less non-metallic inclusions and less component segregation by the above-described continuous slab casing, it is important to stir the molten metal in the middle of the solidification process as required. Also, the molten metal stirring in case of the slab that is larger in a cross-sectional area and moreover larger in length-to-width ratio of the cross-sectional shape (e.g., the ratio of the length of the longer side wall to the length of the shorter side wall being 5 or more) would be highly liable to such problem as occurrence of center segregation, center cross-sectional cracks as well as degradation of machinability, unlike the case of strands that are small in cross-sectional area and moreover nearly square in cross-sectional shape such as blooms or billets, for this reason there has been a need for stirring the molten metal as required.

Recently, as the life-span of submerged nozzles or the like becomes longer, the service life of the submerged nozzles or the like becomes durable to the casting with a plurality of ladles, which makes it possible to continuously cast the different kinds of steels and the strands of the cooling molds in different widths.

Various kinds of structures for stirring the molten metal as required have been proposed for a long time, but there is still no countermeasure enough to deal with the casting when the width or the thickness of the mold are changed.

The applicant of the present invention discloses the continuous slab casting apparatus, in Japanese Patent No. 5,742,992, wherein a rotational mechanism rotates a platform (hereinafter called a base) having a connecting mechanism (hereinafter called a nozzle exchanging-holding mechanism) connecting the submerged nozzle to a slide nozzle mechanism, together with the submerged nozzle, by a specific angle. According to such configuration, as well as the rotational flow can be obtained by keeping a discharge direction of the molten metal discharged from a discharge hole on a lower end of the submerged nozzle toward an objective direction of a longer side direction, it is possible to keep the rotational angle corresponding to the length and the thickness of the longer side.

FIG. 1is a front view of the continuous slab casting apparatus disclosed in Japanese Patent No. 5,742,992, andFIG. 2is a plan view (bottom view) of the apparatus looked up from a bottom. The conventional continuous slab casting apparatus is provided with a slide valve mechanism to adjust the flow quantity of the molten metal flowing into the mold, and the nozzle exchanging-holding mechanism to hold the submerged nozzle guiding the molten metal from the slid valve mechanism to the mold on a lower side of the slide valve mechanism and also to exchange an after-use submerged nozzle with an unused submerged nozzle. The continuous slab casting apparatus disclosed in Japanese Patent No. 5,742,992 is also provided with those mechanisms, and further provided with a nozzle rotational mechanism as described herein after.

The slide valve mechanism is placed between a housing5and a seal case9on a lower surface of a tundish1, and its configuration is well-known, so undermentioned description refers only to necessary parts to the present invention. A slide plate3bis placed between an upper plate3aand a lower plate3c,and slides by a hydraulic cylinder7for sliding, whereby the size of a molten steel hole made on each plate can be changed. Accordingly, it is possible to adjust the flow rate of the molten metal supplied from the tundish1through an upper nozzle2, and supply the molten metal to a submerged nozzle6through a lower nozzle4.

The lower nozzle4is placed at a position corresponding to the molten steel hole on the lower plate3cof the seal case9, and functions as a role of connecting the slide valve mechanism to the submerged nozzle6.

The nozzle exchanging-holding mechanism is incorporated to the base11placed on a lower side of the seal case9.

The base11is integrally formed by connecting two pieces11aand11bwith a connecting bar11c,wherein the pieces11aand11bare arranged on both directions (hereinafter referred to right and left directions, or right and left) perpendicular to a moving direction of the submerged nozzle6(hereinafter referred to a nozzle moving direction: an arrow direction ofFIG. 2) at the exchange of submerged-nozzle. At a center of the right and left pieces11aand11b,a space (hereinafter referred to a moving-connecting space D) is arranged so as to move the submerged nozzle at the exchange of the submerged-nozzle and to be connected to the lower nozzle4at fixing (operating) the submerged nozzle6. A right-and-left width of the moving-connecting space D is corresponding to a right-and-left width of a flange15on an upper end of the submerged nozzle6, and a slide guide14is disposed on an inside of the moving-connecting space D along the nozzle moving direction. The flange15on the upper end of the submerged nozzle6is pressed against the lower surface of the lower nozzle4and held thereon, according to the undermentioned configuration.

On the both right and left sides of the moving-connecting space D under the lower surfaces of the right and left pieces11aand11bof the base11, plural clampers13are supported by clamper pins along the nozzle moving direction, so as to position the tips of the clampers on the lower surface of the flange15of the submerged nozzle6. Coil springs12attached on the base11are arranged on ends of the clampers13, and the tips of the clamper13are biased upward. Accordingly, the lower side of the flange of the submerged nozzle6is biased upward at the tips of the clampers13, and the upper end surface of the submerged nozzle6is tightly attached to the lower surface of the lower nozzle4.

Furthermore, the continuous slab casting apparatus is configured so as to exchange an after-use submerged nozzle6ewith an unused submerged nozzle6nby means of the nozzle exchanging-holding mechanism.

The nozzle exchanging-holding mechanism is configured so that the unused submerged nozzle6ninserted from a guide rail16on an upstream side of the nozzle moving direction moves to a downstream side of the nozzle moving direction, and pushes out the after-use submerged nozzle6eto the guide rail16on the downstream side. At this time, the connecting bar11cof the base11is configured so as not to interfere with the moving of the submerged nozzle6, as shown inFIG. 1.

In the conventional continuous slab casting apparatus, the base11is configured to be fixed on the seal case9, but the apparatus disclosed in Japanese Patent No. 5,742,992 that the present invention presupposes is configured so as to allow the base11to rotate a specific angle by means of the rotation mechanism.

The base11is suspended from the seal case9by a support guide roller22and a support guide21so as to be rotatable around a center axis of the submerged nozzle6, so that driving a driving device (hydraulic cylinder)23fixed on the seal case9under such condition can rotate the base11by a specific angle. Accordingly, the submerged nozzle6held by the nozzle exchanging-holding mechanism rotates, too, and the discharge direction of the molten metal from the discharge hole can be changed according to the conditions.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

When the continuous slab casting apparatus in the present invention is configured to be the same structure disclosed in the Japanese Patent No. 5,742,992, the discharge direction of the submerged nozzle6can be changed arbitrarily. At this time, it is desired that, ideally, the discharge direction changes accurately along with the motion of the driving device23. However, since the submerged nozzle6and the lower nozzle4are designed so as to slide keeping the gas sealing property, the sliding surface receives the frictional resistance at the rotation of the submerged nozzle, and the submerged nozzle6receives the stress in the reverse direction to the driving direction of the submerged nozzle6. On the other hand, when the submerged nozzle6is exchanged, since it is required that the unused submerged nozzle6is smoothly inserted between the right and left slide guides14(to the moving-connecting space D), the submerged nozzle6has a little clearance between the right and left slide guides14. When the clearance is reduced, due to the different size of the flange of the submerged nozzle6caused by the manufacturing process, the problem occurs such that the submerged nozzle6cannot be inserted between the slide guides14(the pieces11aand11b).

The present invention is proposed in view of the above-mentioned conventional conditions, and has an object to provide with an apparatus capable of smoothly inserting the submerged nozzle (into the moving connecting space D) between the slide guides and moving accurately along with the motion of the driving device in order to change the discharge direction.

Solution to Problem

The present invention is assumed that an apparatus for continuous slab casting includes a slide valve mechanism, a submerged nozzle to guide molten metal from a tundish to a mold through the slide valve mechanism, a nozzle exchanging-holding mechanism to move the submerged nozzle through a moving-connecting space D provided to a base under the slide valve mechanism at the exchange of the submerged nozzle and to keep the connection between the submerged nozzle and the slide valve mechanism by pressing the submerged nozzle upward during the operation, and a rotation mechanism to rotate the base of the nozzle exchanging-holding mechanism.

In the apparatus for continuous slab casting, a fixing mechanism fixes the submerged nozzle in the nozzle exchanging-holding mechanism by pressing the submerged nozzle to an inside of the moving-connecting space D of the base and to a direction perpendicular to the moving direction of the submerged nozzle at the exchange of the submerged nozzle.

The fixing mechanism includes elastic materials or actuators provided to one of two pieces forming the moving-connecting space D. The fixing mechanism fixes the submerged nozzle by biasing one side surface of a flange of the submerged nozzle in the moving-connecting space D and pressing an other side surface of the flange against the inside of an other piece by means of the elastic materials or the actuators.

On tips of the elastic materials or the actuators, fixing members are attached in a direction parallel to the moving direction of the submerged nozzle, and the fixing members press one side surface of the flange of the submerged nozzle. Projections projecting to a direction perpendicular to the moving direction are provided on both ends on an abutting surface of the fixing members to the submerged nozzle in the moving direction, and the projections are provided with tapers on the upstream side and the downstream side of the moving direction of the submerged nozzle.

It is desirable that a biasing force of the fixing mechanism is 300 to 5000N (30 kgf to 500 kgf).

Advantageous Effects of Invention

According to the above-mentioned configuration, since the submerged nozzle is fixed by the fixing mechanism, when the rotation mechanism rotates the submerged nozzle by a specific angle in order to change the discharge direction of the submerged nozzle during the casting, the discharge direction can be changed to a desired discharge direction.

In addition, the biasing force of the fixing mechanism is set to a force (300 to 500N) enough that the fixing member can escape to the inverse direction to the biasing direction at the exchange of the submerged nozzle, so that the exchange of the submerged nozzle can be performed easily.

Moreover, the flow discharging through the submerged nozzle can be changed arbitrarily to a specific and desired direction during the casing, and it is possible to give the rotational flow to the molten metal. And where the discharge angle varies due to the accumulation of inclusions on the discharge hole and the mold changes in thickness and width, it is possible to ensure the appropriate discharge angle.

DESCRIPTION OF EMBODIMENTS

FIG. 3is a front view showing an example of embodiments of the present invention,FIG. 4is a plan view (bottom view) looked up from the lower side of the present invention, andFIG. 5is a sectional view of a part of fixing a submerged nozzle. The prior art shown inFIG. 1is configured that the base11of the nozzle exchanging-holding mechanism is held in the seal case9by the support guide roller22, but embodiments of the present invention is configured as follows.

Basically, a ring-shaped support guide21ais fixed on an upper end of the base11, and a support guide21bis fixed on a lower surface of the seal case9in a state that a part of the support guide21bis engaged with the support guide21a,so that the base11is rotatable by sliding the guides21aand21bmutually.

Specifically, a width of moving-connecting space D corresponding to an upper part of the base11covering the lower nozzle4is larger than the width of the flange of the submerged nozzle6, through which the center part of the seal case9can been seen from the lower side. Moreover, a ring-shaped support guide21ais fixed on the upper surface of the base11, and a ring-shaped support guide21bis fixed on the lower surface of the base11, so as to project the support guide21bfrom the lower surface of the seal case9to receive the support guide21a,specifically, (in a state that the support guides21aand21bare engaged each other). Thereby, the base11is held rotatably by the support guide21aand the support guide21b.Like the conventional manner, the rotational force to the base11is given to the base11from the hydraulic cylinder23fixed on the seal case9through a lever27.

Two pieces11aand11bare provided in the right and left directions of the base11that is a platform of the nozzle exchanging-holding mechanism. Two spring holes33aare made on inside of the moving-connecting space D of the piece11a,at two positions of upstream and downstream sides of the nozzle moving direction (an arrow direction inFIG. 5) toward the moving-connecting space D. Coil springs33are inserted in the spring holes33athrough volts (fixture legs32) inserted in the spring holes33a,and a fixing member31is provided on the two coil springs33over the nozzle moving direction. As shown inFIG. 5, the coil springs33are inserted to the volts32, and attached with the fixing member31keeping a moving clearance so as to move in a specific width in the right and left directions. Accordingly, the fixing member31is biased in the right and left directions.

On the other hands, on the inside of the moving-connecting space D of the piece11bof the base11on an opposite side to a side attached with the fixing member31, a slide guide14is formed integrally with the piece11blike the conventional manner. Thereby, when the submerged nozzle6is inserted in the moving-connecting space D, the fixing member31presses a side surface of the flange15of the submerged nozzle6against the right and left directions to push the slide guide14inside of the piece11bto the opposite side. Thereby, the submerged nozzle6rotates by an angle corresponding to the motion of the driving device23when the submerged nozzle rotates.

At the exchange of the submerged nozzle, the submerged nozzle6is pushed to the moving direction. At this time, since the fixing member31is simply pressing the submerged nozzle6by appropriate force described hereinafter, the fixing member31can escape toward the direction inverse to the pressed direction, so that the submerged nozzle can be exchanged easily.

The number of the fixture legs32is two inFIG. 5, but it may be 1, or 3 or more.FIG. 5shows an example using the coil springs33, but the elastic material like plate springs, volute springs, or torsion springs may be employed instead of the coil springs33. In addition, the fixing member31may be pressed by means of various kinds of actuators. As examples of the actuators, hydraulic cylinders, oil-hydraulic cylinders, pneumatic cylinders, solenoid valves can be used.

It is preferable that the biasing force to press the flange15of the submerged nozzle6by the fixing mechanism is 300N to 5000N (30 kgf to 500 kgf). In case of less than 300N, when the driving device for changing the discharge direction rotates the base11, a sliding surface on the lower nozzle4receives the friction resistance, and cannot resist the stress working in the inverse direction to the driving direction, so that the fixing member31cannot fix the submerged nozzle, therefore it is not preferable. In case of 5000N and more, since the fixing member31does not escape even when the submerged nozzle is pushed to the nozzle moving direction at the exchange of the submerged nozzle, the nozzle exchange cannot be performed, therefore it is not preferable. More preferably, the biasing force is 1000N to 3000N.

FIG. 6is an enlarged view of the fixing member31of the fixing mechanism for pressing.

It is preferable that projections37are provided to the upstream side and downstream side of the fixing member31, and moreover, tapers37a,37bare provided to the upstream side and the downstream side of the projections37. Accordingly, the tapers37a,37bmake a space between the fixing member31and the slide guide14on an approaching (withdrawing) side of the submerged nozzle6, so that the flange15of the submerged nozzle6approaching from the upstream side of the moving direction (withdrawn to the downstream side of the moving direction) smoothly approaches (be withdrawn from) between the fixing member31and the slide guide14.

An abutting surface37con the inside looked from a center of the fixing member31is formed to a shape along a periphery of the flange15of the submerged nozzle6, and at the exchange of the submerged nozzle, the periphery of the flange15of the submerged nozzle6is mounted on the abutting surface37cand the submerged nozzle6is fixed tightly.

The projections37provided to both ends of the fixing member31have an effect for preventing the submerged nozzle6from sliding off toward the moving direction at the rotating. On this account, a distance between the projections is set to a value close to a length in the moving direction of the flange of the submerged nozzle. The shape of the abutting surface37cbetween the projections is not limited in particular, but it is preferable to be formed along with an R-chamfered surface where a corner of the periphery of the flange15is subjected to the R-chamfering, or to be formed along with a C-chamfered surface in case of the C-chamfering.

A height of the projection37is desired to be 1 to 5 mm. In case of 5 mm or more, a relief of the fixing member31becomes too large, and the submerged nozzle cannot be exchanged smoothly, therefore it is not preferable.

When the unused submerged nozzle6nis set to the guide rails16of the nozzle exchanging-holding mechanism, it is better to make some clearance between the upstream side of the nozzle moving direction of the slide guide14and the downstream side of the flange15of the submerged nozzle6. Due to the clearance, the setting of the submerged nozzle6is facilitated and the submerged nozzle can be moved easily. On the other hand, when the submerged nozzle6is held at a position to be used during the operation, it is preferable that the center of the submerged nozzle is positioned at a specific place, whereby the flange15of the submerged nozzle6is pressed and fixed on the slide guide14on the opposite side by the fixing mechanism.

According to the above description, it is configured as shown in the enlarged view ofFIG. 6that the abutting surface14cat the center of the slide guide14abutting the flange15becomes a shape projecting a little to the moving-connecting space D, and the tapers are provided to the upstream side and the downstream side of the slide guide, whereby the submerged nozzle can be moved smoothly.

In addition, a configuration as shown inFIG. 5andFIG. 6is preferable, namely, a moving guide hole36for the fixing member31is provided to the piece11aof the base11, and a moving guide35that is a projection mounted by the moving guide hole36is provided to the fixing member31, whereby the fixing member31can be configured to be prevented from moving the downstream direction along with the moving of the submerged nozzle6at the exchange of the submerged nozzle6.

In the above description, the fixing member31is configured to be provided to one piece of the base11, that is, the piece11a,but it may be provided to both pieces, the pieces11aand11b,on the sides facing the nozzle moving space D. In this case, it is configured that the spring holes33are provided to the other side of piece11b,and the coil springs33are inserted in the spring holes33a,and the fixing member31is fixed by the coil springs33. It is nevertheless to say that the slide guides14are replaced with the fixing member31.

INDUSTRIAL APPLICABILITY

As described above, in the apparatus for the continuous slab casting in accordance with the present invention, the submerged nozzle can be tightly fixed on the base that is the plat form of the rotation mechanism when the direction of the discharge hole of the submerged nozzle is changed during the casting (operation), so that the direction can be changed to an accurate angle, and it is possible to perform the stirring of the molten metal appropriately according to the conditions of the mold. Therefore, it is possible to improve the quality of the strands.

REFERENCE SIGNS LIST