Patent Application
20060137849
The present invention relates to an apparatus for urging and holding an immersion nozzle used in continuous casting of molten metal onto a junction surface of a refractory positioned above thereof and exchanging the immersion nozzle without encountering troubles in casting operation, and to an immersion nozzle and closing fire plate to be used in the same.
Conventionally, in pouring and casting molten metal, the immersion nozzle has been used for the purposes of preventing molten-metal oxidation, nonmetallic-inclusion involvement and occurrence of turbulent flow and splash. The immersion nozzle, because of use under severe conditions that its bore contacts flowing molten metal and the outer surface borders on the ambient air, frequently suffers damages of erosion, fracture or breakage. Meanwhile, the alumina or the like in molten steel adheres and deposits on a bore wall of the immersion nozzle to thereby narrow the molten-steel passage. In a conspicuous case, this causes clogging to forcibly interrupt casting operation. For this reason, where casting is scheduled long in time, it is required to exchange the immersion nozzle in the course of casting. The general exchange method of an immersion nozzle includes, for example, removing the old immersion nozzle in a state that casting is once suspended and the tundish is raised to set up a new immersion nozzle, thereafter resuming the casting.
However, recently there is a demand for the capability of swiftly exchanging an immersion nozzle during casting for the purpose of preventing steel-quality deterioration resulting from casting interruption or troubles induced due to cast resuming. In
In this example, the immersion nozzle 52 in use is urged upward by the key-plate rows 51 arranged on both sides thereof and held in a state being urged onto a joint surface 54 of an upper nozzle 56. When to exchange the immersion nozzle 52, a new immersion nozzle 52a is pushed out sideways by a pusher 58 coupled to a cylinder 57, thereby exchanging the immersion nozzle 52 in use. At this time, because the new immersion nozzle 52a slides while being urged onto the joint surface 54 of the upper nozzle 56, even during casting the immersion nozzle can be instantaneously exchanged without leaking molten steel.
However, in the exchanging apparatus of this example, the upper nozzle and the immersion nozzle are pressure-joined at refractory joint surfaces thereof. A gap might occur between the joint surfaces due to local wear upon exchange operation, thermal expansion during use or variation in surface accuracy caused in manufacture. The gap if occurred causes deterioration in steel quality due to air suction through the gap or a danger of leak molten steel through the gap. Generally, in the joint surface of an immersion nozzle, joining is made through a seal member for the purpose of preventing such problems and securing sufficient sealability. However, in the exchange apparatus of this example, because the new immersion nozzle slides while being urged on the upper nozzle, the seal member set in the immersion nozzle is possibly chipped off by the upper nozzle. Thus, it is impossible to apply a seal material.
In the pressure-fit supporting apparatus for an immersion nozzle introduced in JP-B-2-49184, upon exchanging an immersion nozzle a new immersion nozzle is horizontally moved with a spacing to a joint surface of the upper refractory and, in a predetermined position, vertically pushed up and held by pressure-joining. In this apparatus, by previously set a seal member on a joint surface of the new immersion nozzle, the seal member can be interposed between the joint surfaces of the immersion nozzle and the upper refractory. However, in this apparatus, the immersion nozzle is supported by a pressure-joined support part of a metal-frame integrated structure to have a structure that, upon exchange, the immersion nozzle much used is first released of pressure-joining force and lowered downward. For this reason, there is a concern on the problems that, where the apparatus is used to exchange an immersion nozzle in casting, steel leaks from the upper refractory or impossible removal of solidified metal suspended around the nozzle bore. Namely, if solidified metal remains around the upper nozzle bore, a gap occurs at a joint surface to a new immersion nozzle or heavy damage is caused in the joint surface. Even in the presence of a seal member, its function is impeded and hence sufficient sealability is made impossible to obtain.
Furthermore, in JP-A-10-99947, in an apparatus for exchanging an immersion nozzle much used by pushing out with a new immersion nozzle, the new immersion nozzle horizontally moves with a spacing to a joint surface of the upper nozzle positioned above until coming to a predetermined position, and is pressure-joined at the predetermined position. Consequently, a seal member can be used. However, in this apparatus, because the loading of pressure-joining force to the immersion nozzle is only at left-and-right one point in a side surface center of the immersion nozzle and the immersion nozzle during parallel movement is ready to incline due to the resistance to or floating force by molten steel, the pressure-joining force is not easily applied evenly onto the entire seal member on the immersion-nozzle joint surface. Thus, there has been a problem of impediment to sealability.
The problem to be solved in the present invention is to provide, in an immersion nozzle exchanging apparatus for swiftly exchanging an immersion nozzle during casting, a mechanism making possible to use a seal member to a junction surface, prevent steel leak from an upper nozzle and cut the deposit or metal formed around a nozzle bore, which is further made in an apparatus structure capable of evenly loading a pressure-joined force to the entire junction surface, thereby securing a higher sealability in the junction surface between the immersion nozzle and the upper refractory.
In the immersion nozzle exchanging apparatus of the invention, during casting, the immersion nozzle flange at an underside is supported by a plurality of key plates parallel provided on both sides thereof, so that an urge force is acted from the key plates to pressure-join the immersion nozzle to the upper refractory. Meanwhile, upon exchanging an immersion nozzle, in an immersion nozzle exchanging apparatus for horizontally pushing out and exchanging an immersion nozzle much used with a new immersion nozzle, the plurality of key plates for supporting the underside of the immersion nozzle flange respectively have independent urge-force providing mechanisms so that, depending on a horizontal moving position of the immersion nozzle, spring-body upper support shafts are varied in abutment height position by a spring-body supporting seat surface of a slide frame simultaneously horizontally moving having a taper surface in part thereof and a horizontal surface changed in height position in the front and rear thereof to vary a deflection amount of each individual spring body. As a result, an immersion-nozzle urging force caused on each individual key plate is varied by continuously changing a repelling force. Due to this, when exchanging an immersion nozzle, until the new immersion nozzle reaches a predetermined position, an urge force is kept to act such that the immersion nozzle much used remains in a state being urged on the upper refractory joint surface for a time as long as possible, whereby steel leak from the joint surface is prevented and the immersion nozzle much used is slid in a state of keeping the urge force thereby making possible to cut and remove the deposited metal at around the nozzle bore by the upper and lower joint surfaces.
On the other hand, the new immersion nozzle in its movement is not acted upon by an urge force from the key plates supporting the immersion nozzle but in a state of being rested on the key plates, thus moving in a manner keeping a constant space at between the immersion-nozzle joint surface and the upper-refractory joint surface. For this reason, the seal member set on the joint surface of the new immersion nozzle is prevented from falling or being damaged due to contact with the upper refractory joint surface.
Furthermore, in the immersion nozzle exchanging apparatus of the invention, a plurality of key plates are parallel arranged oppositely in the left and right with respect to a push-out direction and to act an immersion-nozzle urging force evenly at an equal interval in the push-out direction. Furthermore, in order for a new immersion nozzle to be pushed from the guide rail on the insertion side onto the key plates, the key plates are provided having taper surfaces at immersion-nozzle contact points such that the key-plate taper surface lower end when a support point of the key plates contacting the immersion nozzle is at an uppermost point is below a guide-rail slide surface while the key-plate taper surface upper end when at a lowermost point is above the guide-rail slide surface.
The immersion nozzle to be used on the immersion nozzle exchanging apparatus of the invention has, in its upper end joint surface central region, a concave surface having a depth of 1.0-10 mm to hold a seal member. Due to the presence of the concave surface, the seal member can be held without falling or deviation in its set position even if somewhat tilted during immersion-nozzle handling.
Also, in the immersion nozzle exchanging apparatus of the invention, a closing fire plate can be arranged which is to be used for emergently stopping molten-steel stream upon ending casting or due to occurrence of a certain trouble during casting. By setting the thickness of the closing fire plate greater than a thickness of the immersion-nozzle flange to have a difference therefrom of at least 12 mm, a sufficient urge-joining force can be exhibited not to leak steel through joint surfaces between upper refractory and closing fire plate thereby closing the nozzle bore thereof. Furthermore, the upper surface of the closing fire plate is featured to have both ends recessed at least in a width of 10 mm and depth of 12 mm perpendicular to the push-out direction, not to interfere with the ball plunger provided for controlling the position of the immersion nozzle.
The immersion nozzle to be exchanged in the course of casting is usually uses a jig for handling. The immersion nozzle must be fixed in direction cooperatively with the jig and firmly gripped, in order to be changed in its carriage upon removed from and attached to the exchanging apparatus and fix a direction of the molten-steel delivery port in setting properly to the apparatus.
For this reason, the immersion nozzle at its neck is covered with a metal case. Projections having a length in a metal-case circumferential direction of at least two-thirds or greater of a bore diameter of the immersion nozzle are provided horizontally and in parallel on a metal case surface in a same side as a molten steel delivery port of the immersion nozzle at two locations of a position spaced at least 95 mm below from an immersion nozzle upper end surface and a position spaced at least 50 mm below thereof, thus offering a convenience to realize secure grip with the handlingjig.
Explanations will be made on the representative embodiments of an immersion nozzle exchanging device, closing fire plate, and immersion nozzle of the present invention.
In
An upper nozzle 4 having a molten-steel discharge port is arranged in the bottom of the tundish 1. In the above, a stopper brick (not shown) is provided to control the flow rate of molten steel. In a lower end surface of the upper nozzle 4, formed is a junction surface 4a to the immersion nozzle 2. This figure shows an attaching state of the immersion nozzle 2 during casting. The immersion nozzle 2 has, at its upper end surface, a junction surface 2a to the upper nozzle 4, and supported at its flange 2b lower surface by the key plates 7 urged by the spring bodies 8 thus being pressure-joined onto the upper nozzle 4.
In
In
Thereafter, the immersion nozzle much used 2 is removed from the mold and a cast operation is resumed.
In an immersion nozzle exchange operation or cast shutdown operation with a closing fire plate, it is sought the immersion nozzle or closing fire plate at a tip abuts against a taper surface of the key plate 7 in the extreme front urging the immersion nozzle much used and moves up the taper surface, to rest on an upper surface of the key plate 7 and simultaneously press this key plate 7 down. As the new immersion nozzle or closing fire plate presses inward the flange of the immersion nozzle much used to move, it similarly moves for the second key plates 7 and the subsequent. For this reason, the key plates 7 of the invention have, at a tip, a taper surface with a proper gradient, thus taking consideration for making smooth the series of operations. Furthermore, the taper surface, if considering the operation of removing the closing fire plate or operation of newly setting an immersion nozzle to the exchanging apparatus, requires to be provided such that, in a lowermost position of the key plate 7 during setting with the closing fire plate, the taper-surface upper end is above a slide-surface level of the guide rail 14 (see the right in
At an inserting and discharge sides of the guide rail 14, the immersion nozzle 2 on the guide rail 14 is immersed in molten steel wherein there are cases that it floats up or inclines from a floating force or stirring force due to molten steel. In the case of floating up or inclination of the immersion nozzle 2, there is a concern that, during movement of the immersion nozzle 2, caused is a trouble upon moving from the guide rail 14 to the key plates 7 or from the key plates 7 onto the guide rail 14 or interference with the upper nozzle 4. Or otherwise, there may be interference with the apparatus main body in the operation of removing the immersion nozzle much used 2 from the mold. In order to prevent such a problem, ball plungers 30 are provided each four above the insert position and discharge position of the immersion nozzle 2 to restrict the upper surface position of the immersion nozzle 2 thus giving consideration to keep a carriage as vertical as possible. In the case of using a closing fire plate as shown in the lower of
The ball plunger 30 in the insertion side are attached 10 mm higher at the deep one as compared to that in the front. This is to allow for a natural inclination upon moving of the immersion nozzle 2 from the guide rail 14 onto the key plates 7. However, it is set in such a height as not to contact the junction surface of the upper nozzle 4 due to excessive inclination. The ball plunger 30 in the discharge position is attached such that its ball positions somewhat above the junction surface of the upper nozzle 4. This is to restrict the upper limit position of the immersion nozzle 2 in order to prevent interference with the exchanging apparatus main body when the pushed-out immersion nozzle much used 2 floats, inclines or is removed. The pushed-out immersion nozzle much used 2 should be immediately removed out of the mold because of the possibility to swiftly resume cast operation.
This immersion nozzle 2 has a flange 2b formed in its upper part. The flange 2b has, in an upper surface, a junction surface 2a to the upper nozzle that is a horizontal surface as a slide surface. Furthermore, a recess (concave surface) 2c for setting thereon a seal member is circularly provided about a nozzle bore core. The recess 2c has a depth of 1.0-10 mm to prevent a seal member from falling even if the immersion nozzle 2 is somewhat inclined. In order to prevent falling of a seal member, the recess 2c is preferred as deep as possible. However, due to the property of the seal member, the increase in its thickness naturally increases the compression amount for securing sealability. From apparatus mechanical restriction and spring deflection amount, the depth has a limitation to 10 mm. On the other hand, 1.0 mm is minimally required to prevent falling. The immersion nozzle 2 has a metal case 2d covering from the flange 2b to a lower part to a neck thereof. Projections 2e are provided in a plurality of circumferential points in an outer periphery of the metal case 2d in a lower part to the neck, to conveniently maintain the position of immersion nozzle upon handling the immersion nozzle 2 to set it by using, for example, a mechanical jig or remove it from the guide rail.
Explaining more concretely, where exchanging the immersion nozzle 2 in the course of cast operation, the new immersion nozzle 2 is usually pre-heated at a high temperature. Also, because the operation would be close to the mold filled with molten steel, it is a general practice to use, as a countermeasure mainly for safety, a jig for holding and handling the immersion nozzle 2. In this case, the immersion nozzle when nearing the mold is in a horizontal position, requiring the change into a vertical position within the mold. Moreover, holding must be tight in order to overcome a floating force from molten steel. Furthermore, the immersion nozzle 2 in a state of being set to the upper refractory (upper nozzle) must be closely coincident in the direction of its molten-steel delivery port 2f with a longer-side direction of the mold.
Namely, the immersion nozzle 2 must be in a structure to vary its position or be tightly griped so as to overcome a floating force due to molten metal when gripped by a jig. Furthermore, in the gripping structure, it is desired to give consideration for naturally determining a direction of the molten-steel ejecting port 2f of the immersion nozzle 2.
As one structure for the above, the immersion nozzle 2 is covered with the metal case 2d in a part from an upper end surface thereof to the lower part to the neck, wherein on a surface of the metal case 2d in the same side as the molten-steel delivery port 2f, projections 2e having a length in a circumferential direction of the metal case 2d of at least two-thirds of an inner bore diameter of the immersion nozzle 2 are horizontally and parallel provided at two points, i.e. in a position of at least 95 mm below the upper end surface of the immersion nozzle (dimension to a projection center) and a position spaced below at least 50 mm from that position. The position of projection 2e is determined from the restriction in space to the immersion nozzle exchanging apparatus or space for removal and insertion from and to the mold. It is preferred to grip the immersion nozzle 2 at a point around 120 mm from the upper end surface. In order to tightly hold the immersion nozzle 2 for freely changing the position thereof and overcome a molten-steel floating force to keep the position, the two projections 2e preferably has a spacing of 50 mm or greater in its center dimensions. The projections 2e can be used for positioning upon gripping the immersion nozzle 2 in a correctly set position by a handling jig such that the direction of its molten-steel delivery port 2f coincides with the direction of a longer side of the mold.
When cast operation is ended or when cast must be suspended due to such a trouble that flow-rate control is difficult during casting or where the nozzle port of the upper nozzle 4 cannot be closed by a stopper brick, a closing fire plate 20 without molten-steel passing port is set up in place of a new immersion nozzle 2. By performing operation in the procedure similar to
In the series of operations, the closing fire plate 20 has a thickness 12 mm greater than the thickness of the flange 2b of the immersion nozzle 2. When the closing fire plate 20 is pushed by the pusher 10d to begin riding onto the first key plate 7, despite in the spring body supporting seat surface 10a position where, during immersion nozzle exchange, the compression force of the spring body 8 corresponding to the key plate 7 is released, because the closing fire plate 20 is great in thickness, it takes a form to be urged onto the junction surface of the upper nozzle 4, further pressing down the key plate 7. Namely, it is moved in a state of compressing the spring body 8 and pressure-joined to the upper nozzle 4 thus being pushed into a predetermined position. By increasing the thickness of the closing fire plate 20, a sufficient urge force is secured for pushing out the immersion nozzle 2 and at the same time stopping molten steel from flowing out. Consequently, where using a closing fire plate 20, the nozzle port of the upper nozzle must be emergently closed. Differently from exchanging the immersion nozzle 2, it moves in a state of being urged onto the junction surface of the upper nozzle 4 during the movement. Furthermore, the urge force onto the junction surface gradually increases. When the closing fire plate 20 reaches a predetermined position, simultaneously a predetermined urge force 500 kg is applied. In setting and moving the closing fire plate 20, the upper-surface both ends thereof are chamfered at least over a width of 10 mm and a depth of 12 mm not to be prevented from moving by the plunger 30.
Although the features of the invention were explained on the basis of
As in the above, the present invention, in an immersion nozzle exchanging apparatus for swiftly exchanging an immersion nozzle during casting, can apply a seal member to the junction surface and cut the metal or the like deposited around the nozzle port. Furthermore, the immersion nozzle can be pressure-joined evenly to the entire junction surface in a state of keeping the immersion nozzle in its position thus conspicuously enhancing sealability in the junction surface and stabilizing steel quality. Moreover, the trouble during immersion-nozzle exchanging. operation could be eliminated. Also, in an emergency, cast stop is possible using a closing fire plate, improving safety. Furthermore, by providing a grip projection on the immersion nozzle or closing fire plate, the handling using a jig became easy and positive.
The present invention is applicable to an immersion nozzle exchanging apparatus capable of securing high sealability in joint surface between the immersion nozzle and the upper refractory, and to an immersion nozzle and closing fire plate to be used thereon.
