JP2010095766A - Apparatus and method for preventing deformation of shell of vessel bottom in rf vacuum degassing vessel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for preventing the deformation of a shell of a vessel bottom in order to improve the service life of a lining brick on the lower vessel in an RF vacuum degassing vessel. <P>SOLUTION: A heat-preventing tool 7 for cutting off radiant heat from a ladle 12 installed at the lower part is provided in the portion of the vessel bottom 3b in the interval of a circulating tube 4 in the lower vessel 3 of the RF vacuum degassing vessel 1, thereby preventing the shell 6 at the interval of the circulating tube 4 from being exposed of the high temperature. The heat-preventing tool 7 is made of a heat-insulative material 8, and further, both end parts at the lower surface of the heat-insulative material 8 are supported with the iron-sheets 9 from the lower part, and the iron-sheets are hang down with hanging tools 10 to the vessel bottom 3b of the lower vessel 3, and a gap 11 is arranged in the interval between the heat-insulative material 8 and the shell 6 of the vessel bottom 3b to restrain the direct heat-conduction onto the shell 3b. The deformation caused by softening and heat-expansion of the shell 6 in the interval of an immersion tube 4 in the vessel bottom 3b, is prevented and the crack and the exfoliation of the lining brick 5 below the inner part of the shell 6 to drastically extend the service life of the lower vessel 3b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, in order to degas the molten steel in the ladle that has been scoured, the upper ladle is provided with two reflux tubes from the lower tank and a dip tube at the tip of the ladle. In the RH vacuum degassing tank to be degassed, the iron shell disposed on the bottom of the lower tank among the lower tank of the RH vacuum degassing tank, the lining brick forming the tank bottom, and the iron covering the exterior thereof Is prevented from the radiant heat of the molten steel and slag in the ladle disposed in the lower part thereof, and relates to an apparatus and a method for preventing the deformation of the iron skin at the bottom of the lower tank.

  In the conventional RH vacuum degassing tank 1 including the upper tank 2a, the intermediate tank 2b, and the lower tank 3 shown in FIG. 2 (a), the tank wall 3a of the lower tank 3 in which the retained molten steel 14 in which the molten steel has accumulated is contained. Since the iron skin 6 covering the lining brick 5 on the bottom 3b is close to the surface of the molten steel 13 and the slag 12 of the ladle 11 arranged under the lower tank 3, the radiant heat is generated from the molten steel 13 and the slag 12 in the ladle 11. In response, the iron skin 6 is softened and deformed, and accordingly, the inner brick 5 in the iron shell 6 of the lower tub 3 is stressed from the iron skin 6 and the inner brick 5 is cracked or peeled off. The life of the brick 5 was remarkably reduced.

  Therefore, in the tank bottom 3b composed of the inner brick 5 around the two reflux pipes 4 of the conventional lower tank 3 shown in FIG. In order to prevent deformation of the iron skin 6, When the change of the thickness of the iron skin 6 is examined and the thickness of the iron skin 6 is increased, there is a problem that the crane load for lifting the RH vacuum degassing tank 1 is exceeded. Therefore, 2. The construction of the brick lining of the lining brick 5 in the lower tub 3 is reviewed, and a ceramic wool sheet 16 serving as a cushioning material is provided between the iron skin 6 and the lining brick 5 as shown in FIG. Although inserted, no clear effect was obtained. Further, as shown in FIG. The brick shape of the lining brick 5 between the two reflux pipes 4 on the tank bottom 3b of the lower tank 3 is reviewed, and the upper side of the lining brick 5 between the two reflux pipes 4 is shortened so that the iron skin 6 due to thermal expansion is obtained. The shape was able to accept stress due to the volume change, but no clear effect was obtained.

  On the other hand, as a method of preventing deformation of the iron shell of the lower tank of the conventional RH vacuum degassing tank, the temperature of the iron shell of the lower tank becomes non-uniform due to the heat transfer from the molten steel in the ladle, and the two reflux tubes Proposed a method to prevent the deformation of the iron skin by blowing a gas body on the iron shell of the lower tank of the RH vacuum degassing tank, in a situation where the molten steel cannot be processed due to interference with the side wall of the ladle due to deformation into the letter C (For example, refer to Patent Document 1).

JP-A-10-287914

  The problem to be solved by the present invention is that the iron shell of the lower tank of the RH vacuum degassing tank is close to the surface of the molten steel and slag in the ladle arranged under the lower tank. Along with this, stress is applied to the lining brick in the iron shell of the lower tank of the RH vacuum degassing tank, and cracking and peeling of the lining brick caused by this stress are eliminated, thereby improving the life of the lining brick. It is to provide an apparatus and a method for preventing deformation of the iron shell of the lower tank of the RH vacuum degassing tank.

  According to the invention of claim 1, the means for solving the above-mentioned problem is that, in the invention of claim 1, the bottom of the RH vacuum degassing tank, particularly the tank bottom between the two reflux pipes for circulating the molten steel This is a device for preventing deformation due to thermal expansion of the iron shell of the lower tank of the RH vacuum degassing tank, wherein a heat shield is provided at the lower part of the iron shell.

  According to a second aspect of the present invention, the heat shield provided at the lower part of the iron skin is made of a heat insulating material, and the lower surface is supported by an iron plate and is suspended from the iron skin. It is a deformation | transformation prevention apparatus by the thermal expansion of the iron skin of the lower tank of a gas tank.

  According to a third aspect of the present invention, the heat protection device suspended from the iron skin is provided with a gap between the iron skin and the suspended iron plate. It is a deformation | transformation prevention apparatus by the thermal expansion of the iron skin of the lower tank of a vacuum degassing tank. By providing this gap, heat conduction from the heat shield is directly prevented, and deformation of the iron skin is prevented.

  In the invention of claim 4, a heat shield for preventing deformation of the iron skin is provided below the iron shell at the bottom of the lower tank of the RH vacuum degassing tank, and is installed at the lower part of the RH vacuum degassing tank. It is a method for preventing deformation due to thermal expansion of the iron shell of the lower tank of the RH vacuum degassing tank, wherein the iron skin is insulated by blocking radiant heat from the pan.

  In the invention of claim 5, a method of disposing a heat shield for preventing deformation of the iron skin at the lower part of the iron skin is to form the heat shield from a heat insulating material and to support the lower surface of the heat insulating material with an iron plate, 5. The method for preventing deformation due to thermal expansion of the iron shell of the lower tank of the RH vacuum degassing tank according to claim 4, wherein the vacuum degassing tank is suspended from the tank bottom of the lower tank.

  In the invention of claim 6, the method of suspending the heat shield from the tank bottom of the lower tank is to suspend the heat shield by providing a gap between the iron shell on the tank bottom of the lower tank and the suspended heat shield. 7. A method for preventing deformation due to thermal expansion of an iron shell of a lower tank of an RH vacuum degassing tank according to the means of claim 5 or 6.

  By adopting the above means, the deformation of the iron shell at the bottom of the bottom tank of the RH vacuum degassing tank is prevented. As a result, the life of the lining brick inside the iron core at the bottom of the conventional lower tank is approximately 39. The life of the lining brick inside the bottom shell of the bottom tank of the present invention is about 51 hours, and the life of the lining brick of the bottom tank of the RH vacuum degassing tank is increased by about 30%. Therefore, the present invention has an excellent effect that has not been achieved in the past.

  First, the principle of the present invention will be described. The means of the present invention shields radiant heat from the ladle 12 installed at the lower part of the RH vacuum degassing tank 1 and prevents heat transfer, thereby preventing RH vacuum desorption. In this method, softening of the iron skin 6 in the lower tank 3 of the gas tank 1 is suppressed, and deformation of the iron skin 6 due to softening is prevented. By the way, between the two reflux pipes 4 projecting downward from the tank bottom 3b of the lower tank 3 of the RH vacuum degassing tank 1, radiant heat is received from the surface of the molten steel 14 and the slag 13 of the ladle 12 installed at the lower part. And since the tank bottom 3b between the reflux pipes 4 is a space where the reflux pipe 4 side is closed by the reflux pipe 4, it tends to become high temperature. Therefore, by providing the heat shield 7 that shields radiant heat at the portion of the tank bottom 3b between the reflux tubes 4, it is possible to prevent the iron skin 6 between the reflux tubes 4 from being exposed to a high temperature. In this case, by using the heat shield 7 as the heat insulating material 8, heat transfer inside the heat shield 7 can be suppressed, and heat insulation of the iron skin 6 at a high temperature can be ensured. Furthermore, if both ends of the lower surface of the heat insulating material 8 are supported by the iron plate 9 from below and the iron plate 9 is suspended and locked to the tank bottom 3b of the lower tank 3 by the lifting tool 10, the heat insulating material 8 and the tank bottom The gap 11 can be provided between the iron skins 6 of the 3b, and direct heat transfer to the iron skin 3b can be further suppressed. As a result, between the reflux pipes 4 of the lower tank 3b of the RH vacuum degassing tank 1 Deformation due to softening and thermal expansion of the iron skin 6 can be further prevented. By preventing the deformation of the iron shell 6 in this way, no stress is applied to the lining brick 5 of the lower tank 3b inside the iron shell 6, so that it does not crack or peel off, and the life of the lower tank 3b is greatly increased. Will be extended.

  The best mode for carrying out the present invention will be described below with reference to the tables and the accompanying drawings. FIG. 2 (b) is a diagram schematically showing the main parts of the RH vacuum degassing tank 1 and the ladle 12 arranged below the RH vacuum degassing tank 1 according to the present invention, as compared with FIG. 2 (a). . As shown in FIG. 2B, the RH vacuum degassing tank 1 includes an upper tank 2a, an intermediate tank 2b, and a lower tank 3, and protrudes from the tank bottom 3b of the lower tank 3 of the RH vacuum degassing tank 1. The dip tube 4a connected to the recirculation tube 4 is inserted into the slag 13 and the molten steel 14 of the ladle 12 arranged at the lower part, and the molten steel 14 is circulated through the RH vacuum degassing tank for vacuum degassing treatment. In this case, ladle smelted molten steel 14 and slag 13 are received in the upper part of ladle 12, and taken from one dip pipe 4 a of lower tank 3 of RH vacuum degassing tank 1 through reflux pipe 4. The molten steel 14 in the pan 12 is sucked into the lower tank 3, vacuum degassed in the lower tank 3, and the molten steel 14 treated in the ladle 12 is circulated from the dip pipe 4 a through the other reflux pipe 4. As shown in FIG. 3, the bottom 3b of the lower tank 3 of the RH vacuum degassing tank 1 has a heat insulating material 8 for the heat shield 7 between the two reflux tubes 4 and the tank bottom 3b on both sides. Place. An iron plate 9 that supports the heat insulating material 8 from below is disposed at the lower part of both sides of the heat insulating material 8, and the iron plate 9 is suspended from the lower tub 3 by the hanger 10 as the heat shield 7. In this case, if a gap 11 is provided between the tank bottom 3b of the lower tank 3 and the heat insulating material 8, heat is not directly transferred from the heat insulating material 8 to the tank bottom 3b, and the heat insulating material is mainly supplied to the tank bottom 3b. It becomes radiant heat from, and the temperature rise of the tank bottom 3b can be suppressed.

  Therefore, as a result of the heat from the molten steel 14 and slag 13 in the ladle 12 being blocked by the heat shield 7, the iron skin 6 stretched on the bottom 3 b of the lower tank 3 of the RH vacuum degassing tank 1 shown in FIG. Is prevented from being heated by being exposed to a high temperature, so that deformation of the iron skin 6 caused by softening of the iron skin 6 can be prevented accurately. As a result, the force due to the deformation of the iron skin 6 is not applied to the lining brick 5, and the crack or peeling of the lining brick 5 is eliminated, and the life of the lower tank 3 is remarkably extended. Thus, by providing the heat shield 7 according to the present invention on the tank bottom 3b of the lower tank 3, it becomes possible to stably perform vacuum degassing for a long period of time. The amount of oxygen in the molten steel can be reduced to 5 ppm, for example, and the amount of oxide inclusions can be greatly reduced, so that the fatigue characteristics of the obtained bearing steel can be greatly extended.

  The case where a space 11 is provided in the bottom 3b of the lower tank 3 of the RH vacuum degassing tank 1 and the heat protection device 7 according to the present invention is installed is taken as a countermeasure, while the conventional RH vacuum degassing tank 1 remains as it is. Table 1 shows the lifetime of the lower tank 3 from the time when the tool 7 is not installed to the time when the vacuum degassing process is performed and the inner brick 5 of the lower tank 3 is cracked or peeled off. In this case, when the dip tube 4a is replaced approximately every 300 minutes for the RH vacuum degassing process, the inside of the lower tank 3 is visually checked for cracking or peeling of the lining brick 5, and the lining brick 5 Consumption was taken out when the remaining brick size was 0 mm, and cracking of the lining brick 5 was taken out when the crack penetrated to the back. In Table 1, the life after countermeasures after installing the heat shield 7 of the present invention is No. 1-No. In 10 runs of 10, the average was 3087 minutes. On the other hand, the life before the countermeasure by the conventional RH degassing tank which does not install the heat shield 7 is No. 1-No. In 7 runs of 7, the average was 2367 minutes. As a result of Table 1, the life of the lower tank 3 of the RH vacuum degassing tank 1 in which the heat shield 7 of the present invention is installed is approximately 30% of that of the conventional RH vacuum degas tank 1 in which the heat shield 7 is not installed. Elongation was obtained.

It is the perspective view which showed the lower tank of the RH vacuum degassing tank by sectional drawing. (A) is a schematic view of a conventional RH vacuum degassing tank installed in a ladle, and (b) is a partial cross-sectional view of an RH vacuum degassing tank having a heat shield of the present invention installed in a ladle. is there. (A) is a side view which shows a lower tank and a heat shield, (b) is a schematic diagram of the bottom view which shows a lower tank and a heat shield. Shows the surrounding part of the reflux tube at the bottom of the lower tank of the conventional RH vacuum degassing tank, and (b) shows a ceramic wool sheet of cushioning material between the iron shell of the tank wall of the lower tank and the lining brick. And it is typical sectional drawing which shows the example which changed and changed the shape of the lining brick between reflux tubes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RH vacuum degassing tank 2a Upper tank 2b Intermediate tank 3 Lower tank 3a Tank wall 3b Tank bottom 4 Circulating pipe 4a Immersion pipe 5 Lined brick 6 Iron skin 7 Heat shield 8 Heat insulating material 9 Iron plate 10 Lifting tool 11 Cavity 12 Ladle 13 Ladle 13 Slag 14 Molten steel 15 Residual molten steel 16 Sheet

Claims (6)

  An apparatus for preventing deformation due to thermal expansion of the iron shell in the lower tank of the RH vacuum degassing tank, wherein a heat shield is provided below the iron shell at the bottom of the tank in the lower tank of the RH vacuum degassing tank.   2. The iron in the lower tank of the RH vacuum degassing tank according to claim 1, wherein the heat shield disposed in the lower part of the iron skin is made of a heat insulating material, and the lower surface is supported by an iron plate and is suspended from the iron skin. Deformation prevention device due to thermal expansion of skin.   3. The lower tank of the RH vacuum degassing tank according to claim 1, wherein the heat shield hung from the iron skin is provided with a gap between the iron skin and the hung iron plate. For preventing deformation caused by thermal expansion of iron skin.   A heat shield for preventing deformation of the iron skin is provided at the bottom of the bottom iron shell of the lower tank of the RH vacuum degassing tank to cut off the radiant heat from the ladle provided at the lower part of the RH vacuum degassing tank. A method for preventing deformation due to thermal expansion of the iron skin of the lower tank of the RH vacuum degassing tank, wherein the iron skin is heat-insulated.   The method of disposing a heat shield for preventing deformation of the iron skin at the bottom of the iron skin is to form the heat shield from a heat insulating material and to support the lower surface of the heat insulating material with an iron plate, and to support the iron plate in the lower tank of the RH vacuum degassing tank. The method of preventing deformation due to thermal expansion of the iron shell of the lower tank of the RH vacuum degassing tank according to claim 4, wherein the method is suspended from the bottom of the tank.   5. The method of suspending and arranging the heat shield on the bottom of the lower tank is characterized in that a space is provided between the iron shell on the bottom of the lower tank and the suspended heat shield to suspend the heat shield. The deformation | transformation prevention method by the thermal expansion of the iron shell of the lower tank of RH vacuum degassing tank of description.

Images