JP2005171281A - Method for adding alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for accurately charging an alloy in an alloy storage at necessary timing. <P>SOLUTION: In the method for adding the alloy, the alloy 114 stored in the alloy storage 112 is added into molten steel 102 in a vacuum vessel 106 in a reduced pressure refining apparatus, this adding method is performed, by which in the case of being the pressure difference between the atmospheric pressure in the inner part of the alloy storage 112 and the atmospheric pressure in the vacuum vessel 106 side at a prescribed pressure having ≥50 hPa, the addition of the alloy 114 into the molten steel 102 is forcedly shut off. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to addition of an alloy in a molten steel vacuum refining apparatus. More specifically, the present invention relates to a technique for accurately adding a desired amount of alloy at a desired timing in a molten steel vacuum refining apparatus.

  In recent years, there has been an increasing need for high-purity steels with a very low content of impurities and non-metallic inclusions. In general, the hot metal produced in the blast furnace is refined in the converter, but it is difficult to achieve a sufficiently high purity and the efficiency is poor only by the converter refining. Therefore, the purity of the hot metal produced in the blast furnace is enhanced by refining treatment called hot metal pretreatment and secondary refining in addition to refining treatment in the converter. At present, the process of blast furnace → hot metal pretreatment → converter → secondary refining is widely adopted as a manufacturing process of high purity steel. In addition to the converter, secondary refining is adopted after refining treatment in an electric furnace.

  As typical equipment for secondary refining, various refining apparatuses of RH type, LF type, DH type, VOD type, and AOD type have been proposed. The RH type refining apparatus is a refining facility that uses a suction type vacuum refining method. The LF refining apparatus is a refining facility that performs refining by immersing electrodes in slag that covers molten steel, heating the slag and molten steel, and blowing argon from a porous plug at the bottom of the pan. The DH type refining apparatus is a refining facility for degassing molten steel by repeating the operation of sucking up the molten steel held in the ladle and the operation of raising the tank and returning the molten steel in the tank to the ladle. The VOD type refining apparatus is a refining facility that applies a refining operation to molten steel inside a ladle placed in a vacuum chamber. The AOD type refining apparatus is a refining facility that performs decarburization by blowing an inert gas together with oxygen gas into molten steel under atmospheric pressure.

  In these secondary refining processes, the components are adjusted by charging the alloy as necessary. In general, the alloy is introduced in such a manner that a predetermined amount of alloy is cut out at a predetermined timing from an alloy storage tank in which the alloy is stored and dropped into molten steel inside the secondary refining equipment.

The input amount and timing of the alloy greatly influence the quality of the molten steel to be refined. Therefore, it is important that the desired amount of the alloy is accurately charged at the desired timing. As a technique relating to accurate alloy introduction, for example, a technique has been proposed in which a hole is provided in the side wall of a tank of a secondary refining facility, and an alloy addition tank communicating with the hole is installed (see Patent Document 1). According to Patent Document 1, it is said that by installing an alloy addition tank, an alloy is deposited on a shelf formed on the inner wall of the tank, and the problem that accurate alloy addition cannot be achieved can be solved.
JP 59-50114 A

  Various methods for adding an alloy have been proposed, but in an RH, DH, VOD, etc. vacuum refining apparatus, the alloy in the alloy storage tank flows into the molten steel at an undesired time. There is a problem. When the vacuum tank to which the molten steel is supplied is depressurized, the pressure on the alloy vacuum tank side and the pressure in the alloy storage tank are controlled to be equal. However, when the pressure in the alloy storage tank rises due to leakage, etc., the alloy in the alloy storage tank is pushed out to the molten steel side by the differential pressure generated between the pressure on the vacuum tank side and the pressure in the alloy storage tank. End up. If such an unscheduled alloy addition occurs, there is a concern that the quality of the molten steel to be refined will deteriorate.

  Therefore, an object of the present invention is to provide means for accurately charging an alloy in an alloy storage tank into molten steel at a necessary time.

The present invention
(1) An alloy addition method of adding an alloy stored in an alloy storage tank to molten steel in a vacuum tank of a vacuum refining apparatus, wherein the pressure of the atmosphere inside the alloy storage tank and the vacuum tank of the alloy An alloy addition method, characterized by forcibly blocking the addition of the alloy to the molten steel when the differential pressure with the atmosphere pressure is a predetermined pressure of 50 hPa or more,
(2) The alloy addition method according to (1), wherein the addition of the alloy is blocked by a valve installed in a pipe through which the alloy to be added flows.
It is.

  With the present invention, unscheduled addition of the alloy is prevented and the required amount of alloy can be accurately added at the required time. For this reason, the quality fall of the molten steel refine | purified is suppressed.

  Hereinafter, the present invention will be described with reference to the drawings. However, the illustrated embodiment is merely one embodiment, and the technical scope of the present invention is not limited to the illustrated embodiment.

  The present invention relates to a method for forcibly blocking the addition of an alloy to molten steel and preventing the addition of an unscheduled alloy based on the atmospheric pressure around the alloy stored in an alloy storage tank. That is, the present invention is an alloy addition method in which an alloy stored in an alloy storage tank is added to molten steel in a vacuum tank of a vacuum refining apparatus, the pressure of the atmosphere inside the alloy storage tank, and the alloy In the alloy addition method, the addition of the alloy to the molten steel is forcibly blocked when the differential pressure from the atmosphere pressure on the vacuum chamber side is a predetermined pressure of 50 hPa or more.

  First, an outline of the present invention will be described. FIG. 1 is a schematic cross-sectional view of an embodiment of an RH type vacuum refining apparatus. The molten steel 102 to be refined is supplied to the ladle 104. A dip tube 108 protruding from the vacuum chamber 106 is immersed in the molten steel 102 inside the ladle 104. When the vacuum chamber 106 is depressurized using a vacuum device (not shown) while the dip tube 108 is immersed in the molten steel 102, the molten steel 102 is sucked into the vacuum chamber 106 through the dip tube 108 due to the pressure difference. A gas blowing tube 110 is connected to the dip tube 108, and an inert gas such as argon gas is supplied to the molten steel 102 through the gas blowing tube 110. The molten steel 102 is circulated by the argon gas.

  On the other hand, the alloy 114 stored in the alloy storage tank 112 is added to the molten steel 102 for component adjustment. A predetermined amount of the alloy 114 is collected by an alloy cutting device 116 such as a rotary feeder at a timing to be added to the molten steel, and is added to the molten steel 102 inside the vacuum chamber. As described above, unscheduled alloy addition causes a deterioration in the quality of the molten steel to be refined. For this reason, it is important to accurately control the addition timing and addition amount of the alloy.

  When the vacuum chamber 106 is not depressurized and is under normal pressure conditions, the pressure inside the vacuum chamber 106 is equal to the pressure inside the alloy storage tank 112. When the atmosphere inside the vacuum chamber 106 is reduced using a vacuum device with respect to the vacuum smelting apparatus in such a state, the pressure of the vacuum chamber 106 and the connecting portion that connects the vacuum chamber 106 and the alloy storage tank 112 is increased. descend. Hereinafter, for the sake of convenience, the pressure of the atmosphere inside the vacuum chamber and the pressure of the atmosphere of the connection portion connecting the vacuum chamber and the alloy storage tank are referred to as “vacuum chamber side pressure”. Moreover, the pressure of the atmosphere inside the alloy storage tank is referred to as “storage tank side pressure”.

  The alloy 114 is held by the alloy cutting device 116 so as not to be discharged from the alloy storage tank 112 at an unscheduled time. However, when a certain pressure difference occurs between the storage tank side pressure and the vacuum tank side pressure, the alloy 114 is drawn into the vacuum tank side due to the pressure difference, and the alloy 114 flows out into the molten steel 102 at an unscheduled time. End up.

  In order to prevent such a problem, a pressure equalizing pipe 118 can be provided. The storage tank side pressure and the vacuum tank side pressure are made uniform by the pressure equalizing pipe 118 that connects the inside of the alloy storage tank 112 and the vacuum tank side of the alloy.

  However, when the increase in the storage tank side pressure is large, the increase in the storage tank side pressure due to the leak cannot be compensated by the uniform pipe 118. For example, when an alloy adheres to the upper lid of the alloy storage tank 112 that is opened and closed during the supply of the alloy, the alloy storage tank 112 is not completely sealed, and the storage tank side pressure greatly increases due to leakage of outside air. In such a case, a portion that cannot be compensated by the pressure equalizing pipe 118 is generated as a differential pressure, and the alloy 114 flows out to the vacuum chamber 106 side by this differential pressure.

  In the present invention, the storage tank side pressure and the vacuum tank side pressure are detected, respectively, and when the differential pressure between the storage tank side pressure and the vacuum tank side pressure is a certain value or more, the molten steel 102 of the alloy 114 is moved to. Is forcibly blocked.

  An overview of the embodiment shown in FIG. 1 will be described. First, the storage tank side pressure is detected by the first pressure gauge 120. On the other hand, the vacuum chamber side pressure is detected by the second pressure gauge 122. The pressure data is transferred to the differential pressure monitoring device 124. In the differential pressure monitoring device 124, the pressure detected by the first pressure gauge 120 and the pressure detected by the second pressure gauge 122 are compared, and if a differential pressure greater than a preset value occurs, the differential pressure is detected. The monitoring device 124 determines that “abnormality exists”.

  Various aspects can be considered for the reaction after it is determined that "abnormal". A lamp installed in the differential pressure monitoring device 124 may be lit. A speaker 126 that issues an alarm according to a command from the differential pressure monitoring device 124 may be installed. In any case, when it is determined that there is “abnormal”, the addition of the alloy from the alloy storage device 112 to the vacuum chamber 106 is forcibly cut off.

  In the present invention, “forced shut-off” refers to an action that makes it impossible for an alloy stored in an alloy storage tank to be added to molten steel by a change applied to a vacuum refining apparatus. means.

  In addition, “forced shut-off” refers to the act of changing the state in which the alloy can be added to the state in which the alloy cannot be added, and the addition of the alloy from the state in which the alloy cannot be added. It is a concept that includes both the act of preventing a change to a possible state.

  The former action is used in an embodiment in which the alloy addition path from the alloy storage tank 112 to the vacuum tank 106 is open in principle. In this embodiment, the supply of the alloy 114 is only controlled by the alloy cutting device 116, and after passing through the alloy cutting device 116, the alloy is automatically added to the vacuum chamber 102. In this embodiment, the alloy addition is forcibly interrupted by closing the valve after it is determined that there is “abnormal”.

  The latter action is used in embodiments where the alloy addition path from the alloy reservoir 112 to the vacuum chamber 106 is closed by a valve 128. This embodiment may be used when the alloy 114 is not added to the molten steel 102 constantly but at regular intervals. When the alloy 114 is added to the molten steel 102 at regular intervals, it is not always necessary to open the pipe connecting the alloy storage tank 112 and the vacuum tank 106. Opening the valve 128 only when adding the alloy 114 prevents the addition of the alloy at an unscheduled time. However, if the differential pressure between the storage tank side pressure and the vacuum tank side pressure is large, the alloy 114 more than the necessary amount flows out to the vacuum tank side when the alloy is cut out after the valve 128 is opened. The problem is that if the differential pressure detected using the differential pressure monitoring device 124 is above a certain value, the valve 128 is not opened, i.e., prevents the alloy from being changed to a state where addition of an alloy is possible. Can be solved by. When it is determined that there is an abnormality, the valve 128 is not opened, and the abnormality is notified by lighting of a lamp or a warning from the speaker 124.

  The valve 128 that forcibly cuts off the addition of the alloy may be manually opened / closed based on a lamp or speaker 126 that informs of “abnormality”, or is automatically controlled by an instruction from the differential pressure monitoring device 124. Also good. After it is determined that “there is an abnormality”, the vacuum refining apparatus is stopped at an appropriate time, the leak around the alloy storage tank 112 is examined, and the cause of the leak is removed. Thereafter, the operation is resumed.

  When the alloy addition method of the present invention is used, deterioration of the quality of molten steel due to unscheduled alloy addition is prevented. Moreover, the yield fall of the molten steel refine | purified is also suppressed. If the abnormality is detected by the quality check of the refined molten steel and then the abnormality is examined, the molten steel from the occurrence of the abnormality to the detection of the abnormality by the quality check becomes a defective product. On the other hand, according to the method of the present invention, when an abnormality occurs, the abnormality can be detected quickly, so that a large amount of molten steel is prevented from becoming a defective product. That is, the yield of the refined molten steel is improved by the method of the present invention.

  Next, the equipment configuration, materials, conditions, etc. used in the method of the present invention will be described in detail. Regarding the selection of equipment configuration, materials, conditions, etc., knowledge already obtained with respect to vacuum refining is referred to as appropriate, and the technical scope of the present invention is not limited to the embodiments described below. In addition, known knowledge can be applied to matters not specifically described. For example, the constituent material of the decompression device is not specifically mentioned, but the same constituent material as in the past can be used. Newly developed component materials may be used.

  As the vacuum smelting device, various vacuum smelting devices such as an RH vacuum smelting device, a DH vacuum smelting device, and a VOD vacuum smelting device are used. The present invention can be applied to various types of refining apparatuses in which the atmosphere around the molten steel to which the alloy is added is reduced in pressure to other refining apparatuses.

  The molten steel discharged from the converter or electric furnace is supplied to the vacuum refining apparatus. The method for supplying molten steel is not particularly limited in the present invention. The shape and size of the ladle to which the molten steel is supplied may be determined according to the type of the vacuum refining device and the amount of molten steel to be processed.

  It does not specifically limit about the component of molten steel. Depending on the quality and purity of the finally obtained steel, after the hot metal preliminary treatment is performed, molten steel having a predetermined purity is supplied. For example, molten steel having a carbon concentration of about 100 to 600 ppm decarburized in a converter is supplied.

  The vacuum refining apparatus has a vacuum tank for degassing from molten steel. The vacuum chamber has an alloy supply port for adding an alloy and an exhaust port for decompressing the inside of the chamber. The shape of the vacuum chamber varies depending on the vacuum refining apparatus.

  In the RH type vacuum refining apparatus, as shown in FIG. 1, normally, two tubes immersed in a ladle are installed in the vacuum tank. Of the two pipes, the molten steel is sucked up from one pipe, and the molten steel sucked up from the other pipe is returned to the ladle. The RH type vacuum refining apparatus is suitable for processing a large amount of molten steel because of its high reflux rate. The refining function may be expanded by improvements such as supplying pure oxygen gas into the vacuum chamber.

  In the DH type vacuum refining apparatus, a single dip tube is installed in the vacuum tank to suck up the molten steel held in the ladle into the vacuum tank. Molten steel is sucked up from the dip tube, the vacuum chamber is raised, and the sucked molten steel is returned to the ladle. This operation is repeated to degas the molten steel.

  In the VOD type vacuum refining apparatus, a ladle to which molten steel is supplied is placed inside a vacuum chamber. VOD type vacuum refining equipment is used for refining special steel that is difficult to refining in the atmosphere. Like a VOD-type vacuum smelting apparatus, the vacuum tank may have a ladle disposed therein.

  As described above, there are various types of vacuum smelting apparatuses, but various vacuum smelting apparatuses that have a vacuum tank in which molten steel is supplied, the atmosphere around the molten steel can be reduced, and an alloy is added to the molten steel. The present invention is applicable. More specifically, the present invention relates to an alloy storage tank for storing the alloy, an alloy supply port for adding the alloy, and a vacuum tank having an exhaust port for decompressing the inside of the tank, and the alloy storage A first pressure gauge for detecting the pressure of the atmosphere inside the tank, a second pressure gauge for detecting the pressure of the atmosphere on the vacuum tank side of the alloy, and an alloy forcibly blocking the addition of the alloy to the molten steel It can be applied to a vacuum refining apparatus having an addition blocking means.

  In some cases, an inert gas such as argon gas is supplied to the molten steel 102 through the gas blowing pipe 110 for degassing the molten steel. The supply amount of the inert gas is not particularly limited. If the specific numerical value about the RH type | formula vacuum refining apparatus is given, argon gas will be supplied to molten steel at the rate of 0.6-15L (Normal) / (min / mol steel ton).

  A vacuum apparatus is used when reducing the atmosphere in the vacuum chamber. The type of vacuum device is not particularly limited. What is necessary is just to install the vacuum apparatus which has an appropriate capability according to the magnitude | size of a vacuum chamber and the pressure in the vacuum chamber at the time of pressure reduction. Although the pressure in the vacuum chamber at the time of pressure reduction is not specifically limited, It shall be about 0.7-70 hPa.

  The alloy supply port installed in the vacuum tank is connected to the alloy storage tank. The alloy used for refining is stored in the alloy storage tank. If two or more kinds of alloys are added to the molten steel, two or more alloy storage tanks may be arranged. Although the shape of an alloy storage tank is not specifically limited, Usually, a hopper is used. The magnitude | size of an alloy storage tank should just be determined according to the addition amount of an alloy. When a large amount of alloy is added, a somewhat large alloy storage tank is required. If it is not time-consuming to replenish the alloy in the alloy storage tank, a small alloy storage tank may be arranged to replenish the alloy frequently.

  At the bottom of the alloy storage tank, a cutting device for adding a predetermined amount of alloy to the molten steel is installed. The alloy cutting device is preferably a rotary feeder. The rotary feeder supplies powder particles by the rotation of the rotary blades. If a rotary feeder is used, the alloy can be supplied at a desired supply rate. Regarding the rotary feeder, for example, “13. Handling of granular material” of “Chemical Engineering Handbook 4th revised edition” (edited by Chemical Engineering Association, published by Maruzen Co., Ltd.) can be referred to.

  The amount of alloy cut out from the alloy storage tank and the timing of cutting out the alloy may be selected according to the refining method and the molten steel to be refined. For example, when an alloy is added only during a period of about 1 minute among several tens of minutes of refining treatment, the alloy cutting device may be operated only during that period.

  The amount of cut out alloy can be controlled by measuring the rotational speed of the rotary feeder, the mass of the alloy contained in the alloy storage tank, and the like. A method of controlling the amount of cut out alloy by changing the rotation speed of the rotary feeder is simple. However, since the addition amount can vary depending on the alloy particle size, the alloy filling rate, and the like, it is preferable to obtain knowledge about the alloy supply amount in advance.

  The type of alloy stored in the alloy storage tank may be determined according to the purpose of refining. Examples of the alloy to be added include an Fe—Si alloy, a Ti alloy, and an Al alloy.

  The particle size of the alloy stored in the alloy storage tank is not particularly limited, but considering the ease of supply and the ease of mixing when added to the molten steel, the particle size is controlled to about 3 to 30 mm. It is preferable. However, the present invention is not limited to this range.

  In the present invention, the storage tank side pressure and the vacuum tank side pressure are measured using a pressure gauge. There are no particular restrictions on the type of pressure gauge installed. For example, a pressure transmitter with a field indicator is used.

  The storage tank side pressure means the pressure of the atmosphere in the alloy storage tank. If the pressure in an alloy storage tank can be measured, it will not specifically limit about the location where a pressure is actually measured. When the alloy storage device is a hopper as shown in FIG. 1, the interface between the stored alloy and the surrounding gas fluctuates up and down by the addition and replenishment of the alloy. In this case, a pressure gauge for detecting the storage tank side pressure may be installed in the upper part of the alloy storage tank so that the pressure gauge is not buried in the alloy.

  The vacuum chamber side pressure means the pressure of the atmosphere on the vacuum chamber side of the alloy. The pressure gauge installed to measure the vacuum chamber side pressure may be installed in a pipe connecting the alloy storage tank and the vacuum chamber, or in some cases, installed inside the vacuum chamber. However, when the inside of the vacuum chamber is depressurized, a certain amount of pressure gradient may be generated from a portion close to the vacuum device to a portion far from the vacuum device. Therefore, it is preferable that the pressure gauge is installed at a position close to the alloy storage tank in order to measure the vacuum tank side pressure. For example, a pressure gauge for measuring the vacuum tank side pressure is installed in a pipe connecting the alloy storage tank and the vacuum tank.

  In the present application, for convenience of explanation, a pressure gauge that detects the storage tank side pressure is referred to as a “first pressure gauge”, and a pressure gauge that detects the vacuum tank side pressure is referred to as a “second pressure gauge”.

  In the present invention, the storage tank side pressure is compared with the vacuum tank side pressure, and the addition of the alloy is forcibly cut off when a predetermined pressure of 50 hPa or more is detected. Here, the differential pressure to be forcibly cut off is defined as 50 hPa or more. If there is a differential pressure of about 50 hPa between the alloy tank side pressure and the vacuum tank side pressure, the alloy may flow out to the vacuum tank. Based on the rule of thumb to increase. However, the differential pressure used as an index for forcibly blocking the addition of the alloy is not particularly limited as long as it is 50 hPa or more. If the outflow of the alloy does not occur up to a differential pressure of about 70 hPa due to improvement of the cutting device or the like, the pressure for forcibly blocking the addition of the alloy may be 70 hPa. The upper limit of the differential pressure to be determined as “abnormal” is not particularly limited, and may be 80 hPa or 100 hPa depending on the case. However, if the differential pressure determined to be “abnormal” is a differential pressure that cannot be substantially generated, a situation that is determined to be “abnormal” cannot actually occur. Therefore, in reality, the upper limit of “predetermined pressure of 50 hPa or more” will be about 100 hPa.

  The differential pressure between the storage tank side pressure and the vacuum tank side pressure can be monitored using a differential pressure monitoring device. The differential pressure monitoring device compares the pressure data measured by the first pressure gauge with the pressure data measured by the second pressure gauge, and if a predetermined differential pressure of 50 hPa or more occurs, “there is an abnormality. Is programmed to determine. The reaction when it is determined that there is “abnormal” may be a method for allowing the worker to recognize it, or a method for automatically blocking the addition of the alloy. It may be a system in which the worker is made aware and the addition of the alloy is automatically cut off.

  As a method for allowing the worker to recognize, there is a method in which an alarm lamp is arranged on the work panel of the vacuum refining apparatus, and when it is determined that “there is abnormality”, the alarm lamp is turned on. If it is determined that there is “abnormal”, a control program may be set up so that an alarm sounds from the speaker. It is of course possible to combine these. That is, when it is determined that there is “abnormal”, the alarm lamp is turned on and an alarm sound is emitted from the speaker.

  In addition, when pressure reduction by a vacuum apparatus is started, a certain amount of differential pressure is generated. In this case, if it is determined that “abnormal” is present and it is desired to prevent an alarm sound from sounding, a control program may be created so that it is not determined that “abnormal” is present when decompression is started. For example, while the pressure detected by the second pressure gauge 122 is decreasing at a certain speed or higher, it may be determined that “abnormal” is not determined.

  The interruption of the addition of the alloy can be controlled by an alloy addition interruption means installed in a pipe through which the added alloy flows. Examples of the alloy addition blocking means include a valve. Means other than the valve may be employed as long as the addition of the alloy can be forcibly cut off. The shape and form of the valve are not particularly limited. For example, a slide type valve or a flapper type valve may be used.

  Forcibly blocking the addition of the alloy, as described above, from the state where the addition of the alloy is possible to the state where the addition of the alloy is impossible and the state where the addition of the alloy is impossible There is a method of preventing a change to a state where an alloy can be added.

  Therefore, the command from the differential pressure monitoring device differs depending on these methods. In a scheme where the addition of an alloy is not possible, the open valve is closed by a command from the differential pressure monitoring device. On the other hand, in a system for preventing a change from a state in which an alloy cannot be added to a state in which an alloy can be added, physical or electrical control is performed so that a closed valve does not open.

  Here, regarding the RH type vacuum refining apparatus of FIG. 1, the control of the pressure reducing refining apparatus when the method of opening the valve only when the alloy is added will be described.

  Molten steel is supplied to the ladle 104. A predetermined alloy 114 is stored in the alloy storage tank 112. A vacuum apparatus is operated and the inside of the vacuum chamber 106 is decompressed. At that time, the valve 128 is closed so that the alloy 114 does not flow out into the vacuum chamber 106 due to a differential pressure generated at the start of pressure reduction. In addition, the differential pressure monitoring device incorporates a control program that does not determine “abnormal” at the start of pressure reduction. At this stage, an alarm sound does not sound from the speaker 126. In addition, the lamp indicating the abnormality of the work panel of the vacuum refining apparatus is not turned on.

  The molten steel is refluxed by the reduced pressure in the vacuum chamber, and the refining process is started. If necessary, argon gas is supplied from a gas blowing tube. When the time for introducing a predetermined alloy is approaching, the differential pressure between the storage tank side pressure and the vacuum tank side pressure measured by the first pressure gauge 120 and the second pressure gauge 122 is measured by the differential pressure monitoring device 124. investigate.

  If the differential pressure is less than a predetermined value of 50 hPa or more, the valve 128 is opened, and a predetermined amount of alloy is cut out from the alloy cutting device 116 and added to the molten steel 102. When the addition of the alloy is completed, the valve 128 is closed and the refining of the molten steel 102 is continued.

  On the other hand, if the differential pressure detected by the differential pressure monitoring device 124 is not less than a predetermined value of 50 hPa or more, the differential pressure monitoring device 124 determines that “there is an abnormality”. In response to a command from the differential pressure monitoring device 124, an alarm sound sounds from the speaker 126. In addition, a lamp indicating an abnormality in the work panel of the vacuum refining apparatus is turned on. The valve 128 is physically locked so that it does not open in normal processing, or it is electrically locked so that it does not open unless a special command is given. The interruption of the addition of the alloy 114 to the molten steel 102 may be manual or automatic, but preferably the valve 128 is automatically locked based on the determination of “abnormal”.

  When an abnormality is detected, the pressure reduction by the vacuum device is temporarily stopped, and the inside of the vacuum chamber is returned to normal pressure. Thereafter, the alloy storage device 112 and other equipment are checked for anomalies to eliminate the cause. For example, when there is a high possibility that the cause of the differential pressure is an alloy attached to the upper lid of the alloy storage tank 112 when the alloy is replenished, the alloy attached to the lid is removed. After closing the lid, the vacuum chamber 106 is depressurized by a vacuum device. Again, the storage tank side pressure and the vacuum tank side pressure are compared using the differential pressure monitoring device 124. If the differential pressure has decreased below a predetermined value, the valve 128 is opened and the addition of the alloy is started.

It is a cross-sectional schematic diagram of one Embodiment of RH type | mold vacuum refining apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 102 ... Molten steel, 104 ... Ladle, 106 ... Vacuum tank, 108 ... Immersion pipe, 110 ... Gas injection pipe, 112 ... Alloy storage tank, 114 ... Alloy, 116 ... Alloy cutting device, 118 ... Pressure equalizing pipe, 120 ... 1st Pressure gauge, 122 ... second pressure gauge, 124 ... differential pressure monitoring device, 126 ... speaker, 128 ... valve.

Claims (2)

An alloy addition method for adding an alloy stored in an alloy storage tank to molten steel in a vacuum tank of a vacuum refining apparatus,
When the pressure difference between the atmosphere pressure inside the alloy storage tank and the pressure of the atmosphere on the vacuum tank side of the alloy is a predetermined pressure of 50 hPa or more, forcing the alloy to be added to the molten steel The alloy addition method is characterized in that the alloy is cut off.   The alloy addition method according to claim 1, wherein the addition of the alloy is blocked by a valve installed in a pipe through which the added alloy flows.

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