JP2005169452A - Method and apparatus for evaluating refractory for continuous casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluating method and an evaluating apparatus with which a refractory-made structural body, such as an immersion nozzle, a long nozzle, can simply and accurately be evaluated. <P>SOLUTION: The evaluating apparatus provided with a melting furnace 1 for melting a metal, an intermediate trough 2 for receiving the molten metal 10 discharged from the melting furnace and also, pouring the received molten metal into a molten metal flowing-out hole 8 of the refractory-made structural body 7, such as the immersion nozzle, a supporting tool 4 for supporting the structural body and a plugging tool 6 for plugging the molten metal flowing-out hole in the structural body, is used. Then, the molten metal flowing-out hole in the structural body is clogged, and the molten metal is filled up into the molten metal flowing-out hole by pouring the molten metal in this molten metal flowing-out hole, and after completing the solidification of the molten metal, the crack and the fissure in the structural body are invested and thus, the spalling property of the structural body is evaluated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for evaluating a refractory structure such as an immersion nozzle or a long nozzle used for continuous casting.

  In continuous casting, refractory nozzles such as long nozzles, immersion nozzles, and sliding nozzles are used to inject molten metal from the ladle into the tundish and from the tundish into the mold. . These nozzles are used for the purpose of preventing the molten metal from being oxidized by air, ensuring stable injection into the mold, etc., and these nozzles are resistant to erosion, abrasion and resistance to molten metal. In many cases, it is composed of an alumina-carbonaceous refractory because of its excellent poling property.

  However, alumina in the molten metal tends to adhere to the alumina-carbonaceous refractory. Therefore, when a nozzle composed of the alumina-carbonaceous refractory is used, the nozzle that becomes the flow path of the molten metal. Alumina adheres to and accumulates on the inner wall of the steel, causing casting to stop due to nozzle clogging, drifting of the flow of molten metal in the mold, and deterioration of slab quality due to peeling and dropping of the adhered alumina. Often occurs.

  Therefore, the effect of improving the quality of nozzles such as immersion nozzles and long nozzles is significant. For example, the development of refractories with the property that alumina is difficult to adhere (hereinafter referred to as "refractory material with difficult adhesion to alumina"), etc. Is widely practiced.

  However, for example, so-called non-carbon materials and spinel materials that do not contain carbonaceous materials have a high coefficient of thermal expansion compared to alumina-carbonaceous refractory materials, and such alumina difficult-to-adhere refractory materials. When using an object, the risk of spalling is extremely high. Therefore, when a test nozzle with anxiety about spalling resistance is used for actual casting, the casting should be stopped due to the destruction of the test nozzle, and further serious operational troubles such as breakout should occur. I must.

Therefore, various methods for evaluating refractories have been performed without using an actual machine. For example, a method of immersing a small refractory test piece in molten steel and measuring the melting loss of the test piece (for example, refer to Patent Document 1) or an immersion nozzle used in an actual machine in a furnace at 1400 ° C. for a predetermined time After being held, a method of investigating cracks in the immersion nozzle and occurrence of cracks by immersing in water (see, for example, Patent Document 2) is performed.
JP-A-7-214256 JP-A-8-132191

  However, in the evaluation method such as Patent Document 1, although it can be evaluated as a refractory material, it cannot be evaluated as a structure with the dimensions used in the actual machine. Is insufficient. Further, in the evaluation method as in Patent Document 2, both the inner wall surface and the outer surface of the immersion nozzle are heated and cooled at the same time, so that it is sufficient as an evaluation of the spalling resistance unlike the thermal shock received by the actual machine. That's not true.

  As described above, the conventional evaluation method cannot reproduce the thermal shock and mechanical shock that a structure such as an immersion nozzle or a long nozzle receives during actual casting, and is made of a refractory material such as an immersion nozzle or a long nozzle. In the present structure, an accurate evaluation has not been performed. Therefore, the operation trouble when using the test nozzle has not been completely prevented.

  The present invention has been made in view of such circumstances, and the object of the present invention is to simply and accurately evaluate a refractory structure such as an immersion nozzle or a long nozzle without fear of operation trouble. It is providing the evaluation method and evaluation apparatus which can be performed.

  The method for evaluating a refractory for continuous casting according to the first aspect of the present invention for solving the above-mentioned problem is one or more structures selected from an immersion nozzle, a long nozzle, and a sliding nozzle, which are refractory structures. The molten metal melted in the melting furnace is injected into the molten metal outflow hole of the body, and the cracking and cracking of the structure are investigated during and after cooling the structure to evaluate the spalling property of the structure. It is a feature.

  The refractory evaluation method for continuous casting according to the second invention is a structure of a molten metal outflow hole of one or more structures selected from a submerged nozzle, a long nozzle, and a sliding nozzle, which is a refractory structure. The outflow side is closed, the molten metal melted in the melting furnace is injected into the molten metal outflow hole on the inflow side of the structure, and the molten metal outflow hole is filled with the molten metal, and the structure is cooled and After cooling, the structure is characterized by investigating cracks and cracks in the structure and evaluating the spalling property of the structure.

  The method for evaluating a refractory for continuous casting according to a third invention is the first or second invention, wherein the molten metal is one selected from iron, aluminum, copper, and alloys of these metals. It is characterized by being.

  An apparatus for evaluating a refractory for continuous casting according to a fourth aspect of the present invention is a melting furnace for melting a metal, a molten metal melted in the melting furnace and discharged from the melting furnace, and the received molten metal An intermediate soot for injecting into the molten metal outflow hole on the inflow side of the molten metal outflow hole of one or more kinds of structures selected from a submerged nozzle, a long nozzle, and a sliding nozzle, which is a refractory structure; And a support jig for supporting the structure.

  The continuous casting refractory evaluation apparatus according to the fifth invention is characterized in that, in the fourth invention, further comprises a closing jig for closing the outflow side of the molten metal outflow hole of the structure. To do.

  According to the present invention, since the actual casting process can be substantially reproduced, it is possible to apply a thermal shock and a mechanical shock substantially equal to those of the actual casting to the refractory structure to be tested. An accurate evaluation almost equivalent to the case where the structure is actually cast becomes possible. Moreover, since it is a simple evaluation apparatus, even if spalling occurs in the refractory structure to be tested, it is not necessary to worry about the influence, and evaluation can be performed without spending extra cost. As a result, the development of a refractory structure such as a submerged nozzle is expedited, thereby providing industrially beneficial effects such as resource saving and energy saving.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing an embodiment of the present invention, and is a schematic diagram of a continuous casting refractory evaluation apparatus according to the present invention. FIG. 1 shows an example of the immersion nozzle 7 for injecting molten metal into the mold as a refractory structure, but even a long nozzle or a sliding nozzle can be evaluated. In addition, these refractory structures to be evaluated are basically the same dimensions as those used in an actual continuous casting machine.

  As shown in FIG. 1, the continuous casting refractory evaluation apparatus according to the present invention receives a melting furnace 1 for melting a metal to obtain a molten metal 10 and a molten metal 10 discharged from the melting furnace 1. At the same time, an intermediate rod 2 for injecting the received molten metal 10 into the inflow side of the molten metal outlet hole 8 of the immersion nozzle 7 and a support jig 4 for supporting the immersion nozzle 7 at a predetermined position below the intermediate rod 2. And a closing jig 6 for closing the discharge hole 9 which is the outflow side of the molten metal outflow hole 8. The intermediate rod 2 is provided with an outflow hole 3 for discharging the molten metal 10 at the bottom. In FIG. 1, the immersion nozzle 7 is disposed inside the storage container 5, and the support jig 4 is fixed to the storage container 5. Here, the storage container 5 is a container for receiving when the molten metal 10 leaks from the immersion nozzle 7, and a refractory or the like is appropriately constructed on the inner wall side.

  The closing jig 6 may have a two-part structure made of refractory or metal as shown in FIG. 2, for example. FIG. 2 is a perspective view showing an example of the closing jig 6. The divided closing jig 6 is arranged so as to cover the outer periphery of the position where the discharge hole 9 of the immersion nozzle 7 is installed, and immersed using bolts and nuts so that the two divided closing jigs 6 are combined. The nozzle 7 may be clamped and fixed. In the closing jig 6 shown in FIG. 2, the combination surface 6 a is uneven, but it may be a smooth surface or may be divided into three or more parts.

  The immersion nozzle 7 is evaluated as follows using the continuous casting refractory evaluation apparatus having such a configuration. First, iron, aluminum, copper, and alloys of these metals are melted in the melting furnace 1 to generate a molten metal 10. Next, the portion of the discharge hole 9 of the immersion nozzle 7 that has been preheated or preheated at a predetermined temperature and time is closed by the closing jig 6 and fixed in the storage container 5 by the supporting jig 4.

  The position of the intermediate tub 2 or the storage container 5 is set so that the upper end opening of the molten metal outflow hole 8 of the immersion nozzle 7 fixed in the storage container 5 is positioned directly below the outflow hole 3 of the intermediate tub 2 in the vertical direction. After the adjustment, the melting furnace 1 is tilted to inject the molten metal 10 into the intermediate rod 2. The molten metal 10 injected into the intermediate rod 2 passes through the outflow hole 3 and falls into the molten metal outflow hole 8, and the discharge hole 9 is blocked by the closing jig 6. Stays inside. Then, the molten metal 10 is poured until the molten metal outflow hole 8 is almost filled.

  The inner wall surface of the immersion nozzle 7 is heated by the injected molten metal 10, and a temperature difference from the outer surface is generated, so that a warm post-gradient is generated inside the immersion nozzle 7. Thereby, a phenomenon equivalent to a temperature gradient at the start of casting in continuous casting can be simulated. In addition, by adjusting the injection speed of the molten metal 10 from the melting furnace 1 to the intermediate rod 2 or the diameter of the outflow hole 3, a physical impact on the immersion nozzle 7 at the start of continuous casting is also simulated. Is possible.

  When the immersion nozzle 7 starts to be heated by the heat of the molten metal 10 in the molten metal outflow hole 8, the surface inspection of the immersion nozzle 7 by visual observation or the like is started. The surface inspection is continued even when the molten metal 10 in the molten metal outflow hole 8 is solidified and the surface temperature of the immersion nozzle 7 is lowered. Further, after the molten metal 10 in the molten metal outflow hole 8 is solidified and the immersion nozzle 7 is cooled, the surface of the immersion nozzle 7 is visually inspected, or the immersion nozzle 7 is cut and the refractory composition is observed. The crack or crack of the inside and the surface of the immersion nozzle 7 is investigated by performing non-destructive X-ray inspection of the immersion nozzle 7 or the like. By doing in this way, the spalling resistance of the immersion nozzle 7 can be evaluated, and it becomes possible to determine the durability in an actual continuous casting machine.

  In this case, the spalling resistance of the immersion nozzle 7 can be evaluated by a method in which the molten metal 10 is not retained in the molten metal outflow hole 8 by the closing jig 6 and a constant amount of the molten metal 10 is continuously injected. . However, in this case, compared with the method in which the molten metal 10 is retained in the molten metal outflow hole 8, the required mass of the molten metal 10 increases. Further, in order to simplify the processing of the molten metal 10 flowing out from the discharge hole 9, it is preferable to separately install a container for receiving the molten metal 10 flowing out from the discharge hole 9.

  The method of the present invention can also be applied to a long nozzle for injecting molten metal from a ladle into a tundish and a sliding nozzle for injecting molten metal from a tundish into a mold. However, in the long nozzle and the sliding nozzle, there is nothing corresponding to the discharge hole 9 of the immersion nozzle 7, and there are merely opened holes above and below the molten metal outflow hole 8, so that the molten metal outflow hole 8 is blocked. It is necessary to change the shape of the closing jig from the above description. For example, mounting hardware is installed on the outer surface of the long nozzle and sliding nozzle, a bolt is attached to the mounting hardware and extends downward, the bolt is passed through a flat metal plate, and the metal plate is fitted to the bolt. What is necessary is just to make it press on the molten metal outflow hole 8 with the nut to match. The sliding nozzle is composed of a fixed plate, a sliding plate, a rectifying nozzle, and the like, and these may be assembled and used as an evaluation test material, or may be evaluated individually.

  In addition, this invention is not restricted to the thing of the form demonstrated above, A various change is possible. For example, the molten metal 10 is injected from the melting furnace 1 into the intermediate furnace 2, but a holding furnace is provided, and the molten metal 10 melted in the melting furnace 1 is once injected into the holding furnace and then injected into the intermediate furnace 2 from the holding furnace. You may make it do. Further, a stopper or the like for adjusting the flow rate of the molten metal 10 may be disposed in the outflow hole 3 of the intermediate rod 2. Further, the structure of the support jig 4 is not limited to the above structure, and any structure can be used as long as it can support a refractory structure for continuous casting including the immersion nozzle 7. It doesn't matter.

  Using the refractory evaluation apparatus for continuous casting shown in FIG. 1, the immersion nozzle (hereinafter referred to as “nozzle A”) that has been used in the past, the prototype immersion nozzle B (hereinafter referred to as “nozzle B”), and the prototype An evaluation test of three types of immersion nozzles of the immersion nozzle C (hereinafter referred to as “nozzle C”) was performed. The dimensions of these immersion nozzles are all the same as the dimensions of the immersion nozzle used in the actual machine.

  3, 4, and 5 show the structures of nozzle A, nozzle B, and nozzle C, respectively. As shown in these drawings, the nozzle A is an immersion nozzle having a one-phase structure made of an alumina-graphite refractory 11, and the nozzle B is an alumina-graphite refractory on the inner wall side where the molten metal outflow hole 8 is formed. Nozzle C having a two-phase structure in which a refractory 12 having a higher coefficient of thermal expansion than that of the product is disposed and an alumina-graphitic refractory 11 is disposed on the outer side of the refractory 12 is provided on the inner wall side where the molten metal outlet hole 8 is formed. 2 is a submerged nozzle having a two-phase structure in which a refractory 13 having a thermal expansion coefficient larger than that of the refractory 12 disposed on the inner wall side of the nozzle B is disposed, and an alumina-graphite refractory 11 is disposed on the outside thereof. .

  [C]: 0.07 mass%, [Si]: 0.01 mass%, [Mn]: 0.25 mass%, [P]: 0.01 mass%, [S]: 0.015 mass% Molten steel was melted in a melting furnace and heated to about 1700 ° C. After the nozzle to be evaluated was heated with a gas burner in advance, the discharge hole of the immersion nozzle was closed with a closing tool made of refractory, and molten steel was injected into the molten metal outflow hole 8. The temperature of the molten steel flowing out from the intermediate punch was 1550 ° C.

  As a result of visual observation of the surface of the immersion nozzle immediately after pouring the molten steel, no cracks or cracks were found in the nozzle A and the nozzle B, but the nozzle C had a fine length of about 10 to 30 mm. Several cracks were observed. In addition, after the injected molten steel was solidified, the immersion nozzle was cut out, and as a result of non-destructive X-ray inspection and observation of the refractory structure, the nozzle A and nozzle B had cracks and cracks inside the immersion nozzle. Although not seen, in the nozzle C, several fine cracks having a length of about 10 to 30 mm were observed inside the immersion nozzle.

  From these results, it was evaluated that nozzle A and nozzle B have high spalling resistance, while nozzle C has low spalling resistance.

  Based on these results, molten steel was cast using an actual continuous casting machine using nozzle A, nozzle B, and nozzle C. The continuous casting machine in which casting was performed and the casting conditions were the same for all three nozzles.

  As a result, since the nozzle A is a conventionally used product that is normally used, the continuous casting operation can be performed without any problem. The nozzle B is a nozzle in which the refractory 12 having a higher thermal expansion coefficient than the alumina-graphite refractory is disposed on the inner wall side, but the casting could be completed without causing cracks in the nozzle. .

  On the other hand, in the nozzle C in which the refractory 13 having a higher thermal expansion coefficient than the refractory 12 is arranged, a large amount of bubbles are generated on the molten steel surface in the mold immediately after the start of casting, and 10 minutes have elapsed since the start of casting. At that time, the nozzle C was broken and forced to stop casting. This is because a crack occurred in the nozzle C at the start of casting due to a physical and thermal impact at the start of casting, and the crack extended and led to breakage of the nozzle. The bubbles generated from the molten steel surface in the mold at the start of casting were those in which Ar gas blown into the immersion nozzle flowed out from the cracked portion of the immersion nozzle in order to prevent alumina adhesion to the immersion nozzle.

  The result of casting in the actual machine and the result of evaluation by the continuous casting refractory evaluation apparatus according to the present invention show the same tendency, and the refractory structure for continuous casting is simply and accurately evaluated by the present invention. It was confirmed that it was possible.

It is a figure which shows embodiment of this invention, Comprising: It is the schematic of the refractory evaluation apparatus for continuous casting which concerns on this invention. It is a perspective view which shows one example of the jig for closure for plugging up a discharge hole. FIG. 2 is a schematic diagram of a nozzle A used in Example 1. FIG. 3 is a schematic diagram of a nozzle B used in Example 1. 2 is a schematic diagram of a nozzle C used in Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Melting furnace 2 Intermediate iron 3 Outflow hole 4 Support jig 5 Storage container 6 Closure jig 7 Immersion nozzle 8 Molten metal outflow hole 9 Discharge hole 10 Molten metal

Claims (5)

  A molten metal melted in a melting furnace is injected into a molten metal outflow hole of one or more types of structures selected from immersion nozzles, long nozzles, and sliding nozzles, which are refractory structures. A method for evaluating a refractory for continuous casting, characterized by investigating cracks and cracks in a structure during and after cooling to evaluate spalling properties of the structure.   The molten metal outflow side of one or more types of structures selected from immersion nozzles, long nozzles, and sliding nozzles, which are refractory structures, is closed, and the molten metal on the inflow side of the structure is closed. The molten metal melted in the melting furnace is injected into the outflow hole, and the molten metal is filled in the molten metal outflow hole. During and after cooling the structure, the structure is checked for cracks and cracks. A method for evaluating a refractory for continuous casting, characterized by evaluating spalling properties.   The refractory material for continuous casting according to claim 1 or 2, wherein the molten metal is one selected from iron, aluminum, copper, and alloys of these metals. Method. A melting furnace for melting metal;
At least one selected from a submerged nozzle, a long nozzle, and a sliding nozzle, which is a structure made of a refractory, and receives the molten metal melted in the melting furnace and discharged from the melting furnace. An intermediate punch for injecting into the molten metal outlet hole on the inflow side of the molten metal outlet hole of the structure of
A support jig for supporting the structure;
An apparatus for evaluating a refractory for continuous casting, comprising:   The refractory evaluation apparatus for continuous casting according to claim 4, further comprising a closing jig for closing the outflow side of the molten metal outflow hole of the structure.