JP2006255742A - Continuous casting method through tundish - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous casting method through a tundish which is advantageous to perform the good continuous casting of molten steel. <P>SOLUTION: In the continuous casting method through the tundish, the tundish 1 with a blowing plug 2 fitted to the inner wall part 12, is used and the molten steel in a ladle is poured into the inner part of the tundish 1, and thereafter, the molten steel in the tundish 1 is poured into a mold to perform the continuous casting. After pouring the molten steel in the tundish 1 into the mold, a water-cooling process, in which the water is sprayed into the tundish 1 for removing the remained steel or remained slag in the tundish 1, is performed. Thereafter, the blowing plug 2 is removed from the inner wall part 12 of the tundish 1 in a state in which the substantial temperature of the blowing plug 2 is kept ≥120°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a continuous casting method using a tundish.

  In Patent Document 1, first continuous casting is performed in which molten steel is injected into a mold through a nozzle refractory provided at the bottom of a tundish that holds molten steel, and then continuously cast. , A method of performing second continuous casting by removing residual steel slag such as metal and slag. According to this method, after completion of the first continuous casting, the remaining steel slag remaining in the tundish is removed and the tundish is repaired, and after the tundish is preheated, the second continuous casting is performed. Yes.

In Patent Document 2, after continuous casting is completed using a tundish, the tundish is supplied again with a solid additive that lowers the melting point of the remaining steel and the like remaining in the tundish and improves the fluidity. A method of use is disclosed. According to this thing, the removability of the remaining steel etc. in a tundish can be improved.
Japanese Patent Laid-Open No. 10-225765 Japanese Patent Laid-Open No. 5-177316

  The industry is further developing a continuous casting method using the tundish. This invention is made | formed in view of the above-mentioned situation, and makes it a subject to provide the continuous casting method by a tundish advantageous in performing continuous casting of molten steel favorably by reusing a blow plug. .

The continuous casting method using the tundish according to the present invention uses a tundish with a blow plug attached to the inner wall, injects the molten steel in the ladle into the tundish, and then pours the molten steel in the tundish into the mold. In the continuous casting method by tundish for continuous casting,
A water-cooling process in which the molten steel in the tundish is poured into a mold and then water is cooled in the tundish to remove residual steel or residue in the tundish;
After the water cooling step, a removal step of removing the blow plug from the inner wall portion of the tundish is performed in a state where the substantial temperature of the blow plug is maintained at 120 ° C. or higher.

  The blow plug may be formed of a ceramic porous body having a large number of air-permeable pores, or may have a slit serving as an air passage. If gas is blown into the molten steel of the tundish from the blow plug, the soot in the molten steel is levitated, so that continuous casting can be performed satisfactorily.

  When the spray plug is sprayed with water, the tip of the spray plug that has been sprayed with water is cooled instantaneously, but if the spraying is stopped, the heat accumulated in the inner wall of the spray plug or tundish As a result of the transmission, the tip surface of the blowing plug is heated to a certain temperature range (substantially temperature). Therefore, the substantial temperature of the blow plug referred to in the present specification refers to the temperature of the blow plug when the heat stored in the blow plug and the inner wall of the tundish is taken into consideration. If the actual temperature of the tip surface of the blowing plug is 120 ° C or higher, liquid water impregnated on the surface and inside of the blowing plug becomes vapor and separates from the blowing plug, so that liquid water remains in the blowing plug. Is suppressed.

  In the water cooling step, the molten steel in the tundish is poured into a mold and continuously cast, and then water is cooled on the inner wall of the tundish to remove the remaining steel or residue of the tundish. Since the remaining steel or residue remaining in the tundish is cooled, it becomes easy to remove the remaining steel or residue. And after a water cooling process, a blowing plug is removed from the inner wall part of a tundish in the state which maintained the substantial temperature of the blowing plug at 120 degreeC or more. In this case, since the substantial temperature of the blowing plug is maintained at 120 ° C. or higher, liquid water is suppressed from remaining on the surface and inside of the blowing plug. For this reason, when the removed blowing plug is attached to the inner wall portion of the tundish again, problems caused by liquid water remaining in the blowing plug are prevented.

  According to the continuous casting method using the tundish according to the present invention, when the blowing plug is attached to the inner wall portion of the tundish, problems caused by liquid water remaining in the blowing plug are prevented. Thereby, even if the blow plug removed from the tundish is reattached to the tundish, continuous casting can be performed satisfactorily.

  Embodiments of the present invention will be specifically described below with reference to the drawings. As shown in FIG. 1, a tundish 1 having a bottomed container shape in which a blow plug 2 is attached to an inner wall portion 12 is used. The tundish 1 has an iron skin 11 having a bottomed container shape, and an inner wall portion 12 formed of a refractory lined on the inner wall surface of the iron skin 11. The blow plug 2 is embedded in the bottom wall portion 13 of the inner wall portion 12 of the tundish 1. And in the case of continuous casting, the molten steel M of the ladle 300 arrange | positioned above the tundish 1 is inject | poured in the storage chamber 1c of the tundish 1. Then, the molten steel M in the storage chamber 1 c of the tundish 1 is poured into the continuous casting mold 5 through the passage of the sliding nozzle 3 and the passage of the immersion nozzle 4. Thereby, a continuous cast piece is formed. In such continuous casting, a bubbling gas is blown into the molten steel M of the tundish 1 from the blowing plug 2 to float the soot and the like in the molten steel M. Thereby, mixing of soot is suppressed and the quality of continuous casting can be improved.

  As shown in FIG. 2, the blow plug 2 is detachably embedded in the bottom wall portion 13 of the tundish 1 through the upper tuyere 14 and the lower tuyere 15. The upper tuyere 14 has a conical surface 14i formed of an inclined surface whose inner diameter decreases as it goes upward. In addition, 100 is a ring-shaped holding brick that supports the bottom surface 2b of the blow plug 2, and 101 is fixed to the iron skin 11 of the tundish 1 with a fixture 104 such as a bolt to support the bottom surface 101b of the pressing brick 100. It is a holding plate. 201 and 202 are bricks constituting a part of the bottom wall portion 13.

  As shown in FIG. 2, the blow plug 2 is made of a metal that covers a plug body 22 formed of a porous ceramic body having air permeability having a large number of pores 21 communicating with each other, and an outer peripheral wall surface of the plug body 22. A cylindrical body 23, a castable layer 24 that is a coating layer that covers the cylindrical body 23 and the plug body 22, and a metal or ceramic pipe body 25 that holds the plug body 22 and the castable layer 24 are provided.

  The pipe body 25 includes a gas passage 26 that allows bubbling gas to pass therethrough and is supplied to the plug body 22, and a coupler 27 that serves as a joint connected to the gas supply side. The cylindrical body 23 has an engaging body 28 having a different cross-sectional shape (cross-sectional V shape) that is integrally engaged with the castable layer 24. The outer peripheral wall surface 22p of the plug body 22 is a conical surface whose outer diameter decreases toward the tip. The outer peripheral wall surface 24p of the castable layer 24 is a conical surface whose outer diameter decreases toward the tip. When the blow plug 2 is attached, the outer peripheral wall surface 24p of the castable layer 24 of the blow plug 2 faces and engages with the conical surface 14i of the upper tuyere 14 constituting a part of the bottom wall portion 13. In this case, the mounting position of the blow plug 2 is restricted.

  In the blow plug 2, the bottom layer 24 m of the castable layer 24 is engaged with the cylindrical body 23. For this reason, if the pipe plate 25 is pulled downward (in the direction of the arrow W1) along the length direction with the presser plate 101 removed from the tundish 1, the plug body 22 and the castable layer 24 move in the same direction. Therefore, the blow plug 2 is removed downward (directly below) from the bottom wall portion 13 of the tundish 1.

  According to the present embodiment, the tip portion of the blow plug 2 other than the plug main body 22 is provided with the protective material layer 29 for deficiency suppression having a buffer function. In other words, the defect-suppressing protective material layer 29 is laminated by applying and solidifying a coating material having a carbon-based fluidity on the tip surface 24 e of the castable layer 24. For this reason, in the removal process and the reattachment process, the loss of the blow plug 2 is suppressed. In addition, in order to ensure the gas blowing property of the plug main body 22, the protective material layer 29 is not coat | covered by the front end surface 22e (surface facing the molten steel M) of the plug main body 22. FIG.

  After the molten steel M in the storage chamber 1c of the tundish 1 is poured into the mold 5 and continuous casting is performed, the tundish 1 in which the molten steel M is empty is transferred to the tundish maintenance yard, and a water cooling process is performed. When the water cooling step is performed, the molten steel M basically does not remain in the storage chamber 1c of the tundish 1. In the water cooling step, cooling water is cooled from the water supply device to the inner wall portion 12 and the blowing plug 2 of the tundish 1 for a certain time. As a result, the remaining steel or residue remaining on the inner wall portion 12 of the tundish 1 is cooled, so that the remaining steel or residue is mechanically removed. In this case, the actual temperature of the blow plug 2 is maintained at 120 ° C. or higher, particularly 180 ° C. or higher. Here, when water is applied to the blow plug 2, the tip surface of the blow plug 2 to which water has been applied is cooled, but if the water spray is stopped, heat is stored in the blow plug 2 or the inner wall 12 of the tundish 1. Due to the transfer of heat, the front end surface of the blowing plug 2 (surface facing the storage chamber 1c) is heated to a constant temperature range and becomes a substantial temperature. In this case, the upper limit temperature of the actual temperature of the blow plug 2 can be 800 ° C., in particular 650 ° C., 550 ° C., 350 ° C.

  After the water cooling process or during the water cooling process, the temperature of the blow plug 2 is determined. In this case, the determination may be performed with the naked eye or by measuring the temperature with a measuring device such as a temperature sensor. Then, under the condition that the actual temperature of the blow plug 2 is maintained at 120 ° C. or higher, the water cooling is stopped, the removal process is performed, and the blow plug 2 is removed from the inner wall portion 12 of the tundish 1. In addition, the tundish 1 can be repaired appropriately after the water cooling step.

  According to this embodiment, since the substantial temperature of the blow plug 2 is maintained at 120 ° C. or higher in the water cooling step and the removal step described above, even if liquid water is impregnated in the blow plug 2, Since the vaporization is promoted, the liquid water is suppressed from remaining in the blow plug 2. For this reason, when the blowing plug 2 is attached to the inner wall portion 12 of the tundish 1, problems caused by liquid water remaining in the blowing plug 2 are prevented.

  In the removal step, the fixture 104 is removed and the pressing plate 101 is removed from the iron skin 11 of the tundish 1. Further, without tilting the tundish 1, the blow plug 2 is pulled out downward (in the direction of the arrow W1) at an angle within plus or minus 30 degrees with respect to the vertical direction together with the holding brick 100. Thereby, the blowing plug 2 is removed from the bottom wall portion 13 of the tundish 1. Thus, since the blowing plug 2 is pulled downward at an angle within plus or minus 30 degrees with respect to the vertical direction, the blowing plug 2 can be easily removed, and damage to the blowing plug 2 can be suppressed. In this case, the tip of the blow plug 2 other than the plug main body 22 is provided with a loss suppressing protective material layer 29 having a buffer function, so that the blow plug 2 can be prevented from being broken.

  According to the present embodiment, the air permeability and the deficient state of the plug body 22 of the blowing plug 2 removed from the tundish 1 are determined after performing the above-described removal process. When the blowing plug 2 is impregnated with a large amount of water as a liquid, the air permeability of the plug body 22 of the blowing plug 2 is lowered. For this reason, if the air permeability of the plug main body 22 of the blow plug 2 is determined, the water content of the plug main body 22 of the blow plug 2 that has been subjected to the water washing step can be detected. If the air permeability of the plug body 22 of the blow plug 2 that has been subjected to the water washing step is good, it can be determined that the water as a liquid does not remain in the blow plug 2 to the extent that it causes a problem. If the plug body 22 of the blow plug 2 that has been subjected to the water washing step contains a large amount of water, when the molten steel M is poured into the tundish 1, water as a liquid is vaporized in a large amount, which is not preferable.

  The air permeability may be determined with the naked eye of the judge or may be performed using an air permeability measuring device. Even if it is determined by the naked eye by the determiner, a change in the air permeability of the blowing plug 2 can be predicted, and there is no practical problem. Here, in determining the air permeability of the blow plug 2 removed from the tundish 1, when the air permeability of the new blow plug 2 is 100% as a relative value, the air permeability is a threshold value (for example, 80% Or 70%) or more, it can be determined that the non-defective product can be reattached. Moreover, if the air permeability is less than the threshold value, it is preferable to replace the blower plug 2 with a new one. The threshold value for determining the air permeability can be appropriately changed according to the type and material of the blow plug 2 and the operation level of continuous casting.

  When the air permeability of the blow plug 2 is good and the blown plug 2 is in the allowable range, the reattachment process is performed, and the blow plug 2 is reattached to the inner wall portion 12 of the tundish 1. . In this case, the blow plug 2 is fitted to the attachment hole of the bottom wall portion 13 of the tundish 1 from below to be attached (see FIG. 2). On the other hand, when the removed blow plug 2 is not good in air permeability or chipping condition, another blow plug 2 (preferably new) having good air permeability and not missing is attached to the inner wall portion 12 of the tundish 1. .

  Then, in a state where the blow plug 2 is reattached to the tundish 1, at least the tip of the blow plug 2 or at least the tip of the new blow plug 2 attached to the tundish 1 is heated by a heating means such as a gas burner 350. A plug heating process is performed in which the heating is performed at a temperature higher than or equal to ° C. Thereby, when the molten steel M is inject | poured into the tundish 1, the protection property of the blowing plug 2 can be improved. In addition, the front-end | tip part of the blowing plug 2 means the part which opposes the molten steel M. FIG.

  By the way, when a large amount of liquid water remains on the inner wall portion 12 of the tundish 1 due to the water cooling process, the blow plug 2 attached to the tundish 1 is removed to remove the remaining water. It is necessary to heat the tip to a considerably high temperature range (about 700 to 800 ° C.). In this respect, according to the present embodiment, the actual temperature of the blow plug 2 is maintained at 120 ° C. or higher in the water cooling step, and the actual temperature of the inner wall portion 12 of the tundish 1 is also maintained at 120 ° C. or higher. For this reason, liquid water is prevented from remaining not only on the blow plug 2 but also on the inner wall portion 12 of the tundish 1. Therefore, in injecting the molten steel M into the storage chamber 1c of the tundish 1, the tip of the blowing plug 2 reattached to the tundish 1 may be heated to a temperature region (350 ° C. or higher) at a lower temperature than the conventional one. In this case, the heating temperature can be set to a high temperature region, but since it takes time for heating, productivity is lowered. Examples of the upper limit of the heating temperature include 800 ° C., 700 ° C., 600 ° C., and 500 ° C. in consideration of productivity and heat retention. Therefore, the front-end | tip part of the blowing plug 2 attached to the tundish 1 can be heated at 350-800 degreeC, 350-750 degreeC, 350-700 degreeC, 350-600 degreeC, for example. The inner wall 12 of the tundish 1 can also be heated to this temperature region.

  Thereafter, the molten steel M stored in the ladle 300 is received in the storage chamber 1 c of the tundish 1. In this state, gas is blown into the plug main body 22 of the blow plug 2 from the gas passage 26 of the pipe body 25, and soot and the like in the molten steel M floats with respect to the molten steel M stored in the storage chamber 1c of the tundish 1. The bubbling process is performed. Then, the molten steel M stored in the tundish 1 is poured into the mold 5 to start continuous casting. According to this embodiment, even when the blow plug 2 is reattached to the bottom wall 13 of the tundish 1, continuous casting can be performed satisfactorily.

  In addition, after the molten steel M in the storage chamber 1c of the tundish 1 is emptied and the continuous casting is completed, the tundish 1 is transferred to the tundish maintenance yard as described above, and a water cooling process is performed. Hereinafter, similarly, the air permeability and the deficient state of the blow plug 2 removed from the tundish 1 are determined, the blow plug 2 determined to be good is reattached to the tundish 1, and the blow plug 2 is heated by means such as a gas burner. A plug heating step of heating to 350 ° C. or higher is performed, and then continuous casting is performed. In this way, the blow plug 2 is used repeatedly.

  In addition, according to this embodiment, although the plug main body 22 is formed with the ceramic porous body which has many air-permeable pores 21, it may have not only this but the slit used as a ventilation path. In addition, the present invention is not limited to the embodiment described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention.

The following technical idea can also be grasped from the above description.
-In the blow plug attached to the inner wall of the tundish for continuous casting,
The blow plug is detachable from the inner wall portion of the tundish, and the blow plug includes a plug body formed of a ceramic body having air permeability and a coating layer covering the outer peripheral wall surface of the plug body.
A blow plug characterized in that a protective material layer for suppressing chipping is provided at the tip of the coating layer of the blow plug, and no protective material layer is provided at the tip of the plug body. The air permeability of the plug body is ensured while suppressing damage to the blow plug.

  The present invention can be used for continuous casting of molten steel.

It is a block diagram which shows the tundish vicinity which is performing continuous casting. It is a block diagram of the vicinity of the blow plug embed | buried under the bottom wall part of a tundish.

Explanation of symbols

  In the figure, 1 is a tundish, 12 is an inner wall portion, 2 is a blow plug, 21 is a pore, 22 is a plug body, 5 is a mold, and 29 is a protective material layer.

Claims (7)

In a tundish continuous casting method, using a tundish with a blow plug attached to the inner wall, injecting molten steel in the ladle into the tundish, and then pouring the molten steel in the tundish into a mold for continuous casting ,
A water cooling step of cooling the tundish by pouring water into the tundish to remove the remaining steel or residue in the tundish after pouring the molten steel in the tundish into a mold;
A continuous casting by tundish, wherein after the water cooling step, a removal step of removing the blow plug from the inner wall portion of the tundish is performed in a state where the substantial temperature of the blow plug is maintained at 120 ° C. or more. Method.   In Claim 1, in the said removal process, when the temperature of the said blow plug is determined and the substantial temperature of the said blow plug is hold | maintained at 120 degreeC or more, the said blow plug is removed from the inner wall part of the said tundish. A continuous casting method by tundish characterized by   3. The blow plug according to claim 1, wherein the blow plug is provided on a bottom wall portion of the tundish, and the blow plug is tilted within an angle of plus or minus 30 degrees with respect to a vertical direction without tilting the tundish. A continuous casting method by tundish, characterized by being pulled out and removed with a tundish.   The air blow of the blow plug removed from the tundish is determined after the removing step according to any one of claims 1 to 3, and the blow plug having good air permeability is connected to the inner wall of the tundish. A continuous casting method using a tundish, wherein a reattaching step of reattaching to a part is performed.   In any 1 paragraph of Claims 1-3, after the removal process, the air permeability of the blow plug removed from the tundish is judged, and the blow plug with good air permeability is formed on the inner wall of the tundish. A continuous casting method using a tundish, wherein a remounting step for remounting is performed and another blown plug is attached to the inner wall portion of the tundish when the removed blown plug has poor air permeability.   In any one of Claims 1-5, the plug heating process which heats at least the front-end | tip part of the said blow plug reattached to the said tundish to 350 degreeC or more is implemented, Then, molten steel is made into the said tundish. A continuous casting method by tundish characterized by receiving.   7. The continuous casting method according to claim 1, wherein a tip portion other than the blowing portion of the blowing plug has a protective material layer for suppressing defects.

Images