JP2012037157A - Arc melting equipment and method for manufacturing molten metal by using the arc melting equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide arc melting equipment capable of thermally efficiently melting an iron source and controlling the supply of the iron source from a preheating chamber to a melting chamber, and to provide a method of operating a molten metal using the arc melting equipment.SOLUTION: The arc melting equipment 1 includes a melting chamber 2 for melting an iron source, a shaft type preheating chamber 4 disposed with directly coupled to the melting chamber 2, and an electrode 3, and the equipment 1 is characterized in that: a bottom face of the chamber 4 is formed to have, at least a part of the bottom face, an inclined bottom face 7a having an inclination downward to the melting chamber 2; a shaft frontage dimension H is set to the optimum value for controlling the supply of the iron source; a push-out device 6 for moving the iron source in the chamber 4 in the direction to the chamber 2 is disposed below the chamber 4, and when the push-out device 6 is driven, the iron source is supplied from the chamber 4 to the chamber 2, and when the drive the device 6 is stopped, the supply of the iron source from the chamber 4 to the chamber 2 is stopped. The optimum value of the shaft frontage dimension H is set so as to satisfy a relationship of A≤H≤4A with respect to the maximum length A of the iron source.

Description

  The present invention relates to an arc melting facility and a method for manufacturing a molten metal using the arc melting facility, in which an iron source such as iron scrap or directly reduced iron is melted by arc to manufacture the molten metal.

  Among the arc melting furnaces that melt iron sources such as scrap, in the batch type arc melting furnace, the scrap to be processed is usually charged into the melting furnace main body by buckets in two or three times. After charging the scrap, an arc is generated by the graphite electrode, and the scrap is melted by the heat of the arc. In order to promote melting, oxygen and carbon are blown into the furnace, and chemical reaction heat is added to shorten the melting time and improve productivity. At this time, exhaust gas containing high temperature and unburned components is discharged out of the system from the melting furnace, but the arc melting furnace consumes a lot of electric power. There is a demand for the development of a melting facility that preheats the scrap to be charged, recovers heat, and reduces power consumption. However, in the case of a batch melting furnace, there is a problem that it is difficult to increase the preheating efficiency. In addition, when a large amount of scrap is supplied into the furnace at a time in a batch, since arc discharge is performed on the scrap, power efficiency is reduced.

  Unlike the batch type, as an arc melting facility that continuously supplies an iron source such as scrap and preheats an iron source to be charged using exhaust gas, for example, a cold iron source disclosed in Patent Document 1 ( An iron source) melting facility (arc melting facility) referred to in the present invention is known. This melting equipment includes a melting chamber for melting a cold iron source, a preheating chamber that is directly connected to the upper portion of the melting chamber and preheats the cold iron source with exhaust gas generated in the melting chamber, and a cold iron source in the melting chamber. An arc generating electrode for melting, a cold iron source supply means for supplying a cold iron source to the preheating chamber, a pusher provided at the lower portion of the preheating chamber so as to be able to enter and exit the preheating chamber, and an outlet provided in the melting chamber It comprises a steel mouth. In the melting facility described in Patent Document 1, while supplying the cold iron source continuously or intermittently to the preheating chamber so that the cold iron source is continuously present in the preheating chamber and the melting chamber, The pusher is moved in and out of the preheating chamber filled with the source, and the cold iron source in the preheating chamber is supplied to the melting chamber. When the cold iron source in the melting chamber is melted by the arc and the molten steel has accumulated in the melting chamber, the pusher is stopped, and then the molten steel is heated by the arc to raise the temperature, and then the cold iron source is preheated. The molten steel is discharged in a state where it is continuously present in the chamber and the melting chamber.

  In the above-mentioned continuous supply type melting furnace, when melting an iron source such as scrap, the time when the iron source is changed from a solid state to a liquid state (molten metal) (hereinafter referred to as “melting period”) )) And a time for raising the temperature of the obtained molten metal to a temperature required for the next step (hereinafter referred to as “temperature raising period”). If the temperature of the molten metal being discharged is low, there is a risk that the molten metal will be hindered due to adhesion of solidified metal at the outlet, and during the heating period, the temperature is raised to a temperature sufficiently higher than the melting point of the iron source. To do. However, in a melting furnace (hereinafter referred to as “arc melting equipment having a shaft-type preheating device”) that continuously supplies an iron source as described in Patent Document 1, it is introduced into the furnace during the melting period. Although it is necessary to supply the iron source continuously and smoothly, it is necessary to suppress the supply of the iron source into the furnace during the temperature rising period.

  That is, in an arc melting facility having a shaft type preheating device, the iron source is continuously or intermittently supplied to the preheating chamber so that the iron source is continuously present in the melting chamber and the preheating chamber (preheating shaft). The iron source in the melting chamber is melted by arc. For this reason, an iron source exists in the preheating chamber and the melting chamber even when the temperature is raised and discharged, so that the iron source for the next charge can be preheated, and the iron source can be melted extremely efficiently. However, if the iron source continues to be supplied into the melting chamber even during the temperature rising period, the temperature of the molten metal cannot be increased efficiently. It is necessary to warm. In the melting facility described in Patent Document 1, the supply amount of the iron source into the melting chamber is reduced by stopping the operation of the pusher which is a device for pushing out the iron source from the lower part of the preheating chamber toward the center of the melting chamber. However, the more the furnace shape allows the iron source to be supplied more smoothly, the more the iron source flows into the molten metal even if the operation of the pusher is stopped, and the temperature rise becomes difficult. This is because if the solid iron source is supplied into the molten metal being heated, although it is preheated, the thermal efficiency (temperature rising efficiency) when the molten metal is heated is lowered.

  In addition, molten metal is a metal in a molten state and is a concept including molten steel, molten iron, and the like.

  In the melting equipment described in Patent Document 1, by reducing the contact area between the molten steel and the cold iron source, the melting chamber is tilted so that the side opposite to the preheating chamber is lowered when the molten steel is heated. It is possible to raise the molten steel temperature faster. If the melting chamber is tilted as it is, the collapse of the cold iron source into the molten steel becomes severe and the temperature rise becomes more difficult, but the cold iron source holding means (baffle plate) provided in the melting chamber when the melting chamber is tilted By holding the cold iron source in the melting chamber, the movement of the cold iron source toward the molten steel is hindered.

Japanese Patent Application Laid-Open No. 11-257859

  The cold iron source holding means installed in the high-temperature melting chamber used during tilting described in Patent Document 1 has a risk of causing thermal deformation or melting unless water cooling or the like is performed, while water cooling or the like is performed. It is desirable not to install a mechanism such as a cold iron source holding means from the viewpoint that the thermal efficiency of preheating is lowered by performing. However, as described above, if the melting chamber is tilted without using the cold iron source holding means, the cold iron source flows into the molten steel and collapses and the temperature rise becomes extremely difficult.

  In this way, a shaft type preheating device designed to supply the iron source so that the iron source is continuously present in the melting chamber and the preheating chamber so as to minimize the electric power required for melting the iron source. In the arc melting equipment we have, it is a conflicting requirement to supply the iron source smoothly to the melting chamber during the melting period and to stop the supply of the iron source to the melting chamber during the heating period. If it is used, it is difficult to stop the supply of the iron source to the melting chamber during the temperature rising period and to raise the temperature of the molten metal efficiently.

  The present invention has been made in view of the above-described problems of conventional arc melting equipment, and an object of the present invention is to efficiently melt the iron source and supply the iron source from the preheating chamber to the melting chamber. It is to provide a new and improved arc melting facility capable of controlling the temperature, and a molten metal operating method using the arc melting facility.

  One aspect of the present invention is a direct connection between a melting chamber for melting an iron source and a state in which the iron source is continuously present with the melting chamber in order to preheat the iron source supplied to the melting chamber. An arc melting facility comprising: a shaft-type preheating chamber provided; and an electrode provided in the melting chamber for melting the iron source supplied into the melting chamber; At least a part of the bottom surface of the continuous preheating chamber is formed as an inclined bottom surface having a downward slope toward the melting chamber, the highest position among the connecting portions of the preheating chamber and the melting chamber, and the melting chamber And the shaft bottom dimension H, which is the shortest distance in the arc melting equipment, between the continuous bottom of the preheating chamber and the preheating chamber is set to an optimum value for supply control of the iron source, The iron source supplied from the preheating chamber An extruding device that moves in the direction of the recording electrode is provided. When the extruding device is driven, the iron source is supplied from the preheating chamber into the melting chamber, and when the driving of the extruding device is stopped, the preheating chamber is moved into the melting chamber. In this case, the supply of the iron source is stopped.

  According to one aspect of the present invention, on / off of the supply of the iron source to the melting chamber is switched by drive control of the extrusion device, so that the supply of the iron source to the melting chamber is performed at a desired timing such as a temperature rising period, for example. By stopping the process, the iron source can be dissolved efficiently.

  At this time, in one aspect of the present invention, the optimum value of the shaft opening dimension H is set so as to satisfy the relationship of A ≦ H ≦ 4A with respect to the maximum length A of the iron source. Also good.

  By doing this, when the drive of the extrusion device is stopped and the supply of the iron source from the preheating chamber to the melting chamber is stopped, the iron source flows into the molten metal during the temperature rising period, preventing the occurrence of collapse. The supply of iron source to the melting chamber can be stopped.

  In one embodiment of the present invention, an inclination angle of the inclined bottom surface may be 15 to 45 degrees with respect to a horizontal direction.

  In this way, in order to stop the supply of the iron source, for example, when the drive of the extrusion device is stopped in the temperature rising period, the occurrence of the collapse of the iron source into the molten metal is suppressed, so that The supply of the iron source to the melting chamber is stopped, so that the iron source can be melted efficiently.

  Therefore, as one aspect of the present invention, a melting chamber for melting an iron source, and a shaft-type preheating chamber provided directly connected to the melting chamber so that the iron source is preheated before being supplied to the melting chamber And an electrode provided in the melting chamber for melting the iron source supplied from the preheating chamber, the arc melting equipment comprising a bottom surface of the preheating chamber continuous with the bottom surface of the melting chamber At least a part is formed as an inclined bottom surface having a downward inclination of 15 to 45 degrees with respect to the horizontal direction toward the melting chamber, and the highest position among the connecting portions of the preheating chamber and the melting chamber, The shaft opening dimension H, which is the shortest distance in the arc melting equipment, between the melting chamber and the continuous bottom surface of the preheating chamber has a relationship of A ≦ H ≦ 4A with respect to the maximum length A of the iron source. Set to meet, said At the bottom of the thermal chamber, it is possible to use an arc melting equipment, characterized in that said extruding device for moving the iron source fed in the direction of the melting chamber from the preheating chamber.

  In one mode of the present invention, the upper part of the connecting portion between the melting chamber and the preheating chamber is made of a replaceable part, so that the shaft width dimension can be changed.

In this way, even when the maximum length A of the iron source is changed, the shaft opening dimension H of the arc melting equipment can be set to an optimum value.
Moreover, in one aspect of the present invention, the shortest distance L between the highest position in the connection portion between the preheating chamber and the melting chamber and the electrode is 0.2 A ≦ L with respect to the maximum length A of the iron source. It is good also as satisfying ≦ 5A.

  If it does in this way, generation | occurrence | production of electrode breakage at the time of supplying an iron source to a melting chamber can be prevented.

  Another aspect of the present invention is a method for producing a molten metal using any one of the above-described arc melting equipment, wherein an exhaust gas generated in the melting chamber is introduced into the preheating chamber and the iron source in the preheating chamber Preheating the iron source, driving an extrusion device disposed under the preheating chamber to preheat the iron source, supplying the iron source from the preheating chamber to the melting chamber, and the iron source preheating the iron source A step of melting the iron source by arc heating in the melting chamber to make a molten metal while supplying the iron source to the melting chamber so as to maintain a state existing in the chamber and the melting chamber; And a step of raising the temperature of the molten metal by stopping driving, and a method for producing the molten metal using an arc melting facility.

  According to another aspect of the present invention, the iron source can be supplied to the melting chamber at a desired timing. For this reason, for example, the iron source can be smoothly supplied to the melting chamber during the melting period, and the thermal efficiency can be improved when the temperature of the molten metal in the melting chamber is raised by stopping the supply of the iron source during the temperature rising period.

  According to the present invention, when producing a molten metal using an iron source such as iron scrap, the supply of the iron source from the preheating chamber to the melting chamber can be arbitrarily stopped (can be turned on / off). The molten metal can be efficiently heated during the warm period. Thereby, the operation time can be shortened and the electric power consumption can be reduced while the preheating efficiency of the iron source in the melting period is increased.

It is one Embodiment of the arc melting equipment of this invention, and is a longitudinal cross-sectional schematic diagram of an arc melting equipment. It is one Embodiment of the arc melting equipment of this invention, and is a horizontal cross-sectional schematic diagram of an arc melting equipment. It is one Embodiment of the arc melting equipment of this invention, and is a longitudinal cross-sectional schematic diagram of the arc melting equipment at the time of changing frontage adjustment components. It is a graph which shows the relationship between the operation time (1 / productivity) and the shaft opening dimension H. It is a graph which shows the relationship between operation time and the inclination bottom face angle of a preheating chamber. It is a graph which shows the relationship of the electrode breakage occurrence frequency and the shortest distance L of the highest part and an electrode.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are essential as means for solving the present invention. Not necessarily.

  The inventors of the present invention manufacture the molten metal by efficiently melting the iron source by supplying the iron source so that the above iron source is continuously present in the melting chamber and the preheating chamber. As an arc melting facility that can be used, an extrusion device that moves the iron source from the preheating chamber to the melting chamber in the direction of the arc electrode is provided at the bottom of the preheating chamber, and when the extrusion device is driven, the iron source is supplied from the preheating chamber into the melting chamber. In order to supply the iron source to the melting chamber at an arbitrary timing so that the supply of the iron source from the preheating chamber to the melting chamber is stopped when the driving of the apparatus is stopped, the iron source preheated in the preheating chamber is It has been found that it is important to set the shaft front opening size, which is the size of the front opening portion of the melting chamber to be supplied into the molten metal, to an optimum value that is an appropriate size. And, as the iron source is not supplied in the state where the extrusion device is not operated, the iron source is supplied only when the extrusion device is operated as a relatively small one compared to the conventional case, The iron source can be turned on and off only by controlling the extrusion device. During the temperature rise period, the supply of the iron source into the molten metal is stopped to prevent the iron source from flowing into the molten metal and preventing the collapse of the iron source. The inventors have found that the temperature can be increased efficiently and completed the present invention. It has also been found that it is important to adjust the inclination angle of the inclined bottom surface of at least a part of the bottom surface of the preheating chamber to an appropriate angle in addition to the adjustment of the shaft opening dimension. At the same time, it was found that it is important to adjust the distance between the frontage and the electrode to the size of the iron source. In the above prior art (Patent Document 1), it is described that the preheating chamber is positioned above the melting chamber. However, in one embodiment of the present invention described below, the iron source is installed in the molten metal. Since the entire shaft portion that is preheated without being put into the preheating chamber is used as a preheating chamber, the preheating chamber and the melting chamber are described as being arranged adjacent to each other. This is because the preheating chamber and the melting chamber are continuous, and the only difference is where they are separated. The same is true in that the outlet of the preheating chamber and the inlet of the melting chamber are integrated. In the description of one embodiment of the present invention described below, it is defined so that the portion where the molten metal exists is mainly the melting chamber. The shaft front end is defined as a plane formed at the boundary surface between the preheating chamber and the melting chamber. The shaft frontage and frontage dimensions will be specifically described below with reference to FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  1 and 2 show an embodiment of the arc melting equipment of the present invention, FIG. 1 is a schematic longitudinal sectional view, and FIG. 2 is a schematic horizontal sectional view.

  The arc melting equipment 1 of this embodiment is directly connected to the melting chamber 2 of the iron source, the electrodes 3 (3a, 3b) for melting the iron source in the melting chamber, and the melting chamber 2 for preheating the iron source. And an extrusion device 6 for moving the iron source 5 in the direction of the melting chamber 2 is provided at the lower part of the preheating chamber 4. It has been. In addition to the illustration, a lance for blowing oxygen gas into the melting chamber 2 and a lance for blowing carbonaceous material are provided through the furnace lid 8.

  1 and 2 show the electrode arrangement in the case of a DC arc melting furnace, the electrodes provided in the melting chamber 2 are not limited to the arrangement and number shown in FIGS. In the case of an AC arc melting furnace, there is no furnace bottom electrode 3b, and there are three electrodes 3a on the furnace top side.

  The extrusion device 6 has a drive device (not shown) that moves the iron source 5 in the preheating chamber 4 in the direction of the melting chamber 2, and the drive device is controlled in operation by a control device (not shown). The extrusion device 6 is preferably installed at the lowermost part of the preheating chamber 4 in order to efficiently supply the iron source 5 in the preheating chamber 4 to the melting chamber 2. Specifically, as shown in FIG. 1, it is preferably installed in the vicinity of the front end of the shaft that supplies the iron source 5 from the preheating chamber 4 to the melting chamber 2 along the inclined bottom surface 7 a of the preheating chamber 4. Moreover, it is preferable that the moving direction of the extrusion device 6 is a direction along the inclined bottom surface 7a of the preheating chamber 4, but the extrusion device 6 may be provided with an extrusion angle adjusting mechanism so that the movement direction can be changed. .

  Further, the drive device of the extrusion device 6 is controlled by the above-described control device so that the extrusion device 6 is driven during the melting period in which the iron source is melted to produce the molten metal, and the molten metal is brought to a temperature required for the next process. It is preferable to control so that the driving of the extrusion device is stopped during the temperature rising period in which the temperature is increased.

  By using an arc melting facility in which such a shaft type preheating chamber is directly connected to the melting furnace body, the iron source 5 is maintained so that the iron source 5 is continuously present in the melting chamber 2 and the preheating chamber 4. Can be supplied to the dissolution chamber 2. For this reason, the iron source 5 can be melted efficiently in the melting chamber 2 while continuously preheating with the exhaust gas generated in the melting chamber 2. In addition, by holding the iron source for the next charge in the preheating chamber (shaft) even during the temperature rise period, the iron source can be supplied more continuously, improving the productivity, and recovering the exhaust gas heat Efficiency can be increased and energy efficiency can be improved.

  Note that the iron source is a solid iron source of an object to be melted in an arc melting facility such as iron scrap, direct reduced iron, iron ore, etc., and the iron scrap is, for example, stainless steel scrap, pig iron, mill scale, iron-stretched material, etc. This may occur when a steel maker makes steel or processes, when a steel product is used in a factory, or when a building, car, home appliance, bridge, or the like is dismantled. Such iron scrap is usually traded as a predetermined shape by various processing processes such as compression, cutting and crushing by a scrap trader.

  In the present invention, the iron source 5 is smoothly supplied to the melting chamber, and in the temperature rising period, the supply of the iron source 5 is stopped and the molten metal 9 is quickly heated. The shaft opening dimension H, which is the distance in the height direction, of the shaft opening, which is the connecting portion, is the optimum value.

  In FIG. 1, the shaft opening dimension H is a continuation of the preheating chamber 4 and the melting chamber 2 from the highest portion X which is the highest position in the connecting portion between the preheating chamber 4 and the melting chamber 2 which is a shaft type preheating device portion. It corresponds to the length in the arc melting equipment 1 of the perpendicular P lowered toward the bottom surface 7. In this case, the cross section of the arc melting equipment 1 at the perpendicular P is a shaft front end, and the Q side of the arc melting equipment 1 with respect to the perpendicular P is defined as the preheating chamber 4 and the R side as the melting chamber 2. When a plurality of perpendiculars are assumed, the shortest length is adopted as the shaft opening dimension H. The shaft opening dimension H is preferably set to an optimum value that is an appropriate dimension that satisfies the relationship of A ≦ H ≦ 4A with respect to the maximum length A of the iron source 5.

  When the shaft opening dimension H is increased, the supply of the iron source to the melting chamber is smooth, but the iron source remains in the melt even if the drive of the extrusion device is stopped during the temperature rise of the melt and the use is stopped. It collapses, the thermal efficiency of the temperature rise of the molten metal decreases, the arc efficiency also decreases, and the production efficiency also decreases. Further, if the shaft opening dimension H is large, a large iron source is supplied to the melting chamber, and the risk of electrode breakage increases. When electrode breakage occurs, it is necessary to stop the operation and replace the electrode, which decreases productivity. In addition, the production efficiency is reduced because the amount of the molten metal in the melting chamber increases more than a predetermined amount of molten metal when there is a collapse of the iron source into the molten metal during the temperature rising period as described above. This is because the temperature raising time for raising the temperature of the molten metal to the tapping temperature required in the next step increases. For this reason, H needs to be 4 A or less (4 times or less of the maximum length A of the iron source).

  On the other hand, when the shaft opening dimension H is too small, it becomes difficult to supply the iron source to the melting chamber, and both the production efficiency and the thermal efficiency deteriorate. As an example, when H is less than A, the frontage portion may be blocked, causing trouble in operation. For this reason, in one Embodiment of this invention, it is set as the structure which supplies an iron source in molten metal using the extrusion apparatus 6, However, By setting the shaft front dimension H to the optimal range (A <= H <= 4A). When the drive of the extrusion device 6 is stopped, the iron source is prevented from collapsing, and only when the extrusion device 6 is used, the iron source can be newly supplied into the molten metal. Thereby, supply of the iron source from the preheating chamber to the melting chamber can be arbitrarily stopped (can be turned on / off).

  The maximum length A of the iron source is determined based on the maximum length of the iron source used for melting. The maximum length mentioned here is the maximum value when the length of the iron source is measured from all directions, and is defined as the diameter of the circumscribed sphere of the iron source. Equivalent to. For scraps that serve as iron sources, for example, there are standards defined by JIS G 2401, the Japan Iron Source Association, thickness 3-6 mm x width 500 mm or less x length 1200 mm or less, depending on the type and dimensions. The total of the three sides is classified to 1800 mm or less, and the size is determined to some extent. In this embodiment, the shaft opening dimension H is determined using the maximum length A of the scrap to be melted defined by the above-mentioned standard. However, depending on various factors such as changes in the situation and standards in each country, the market Since the value of the maximum length A of the scrap that circulates varies, the shaft opening dimension H is appropriately determined according to the maximum length A of the scrap.

  On the other hand, the iron source actually processed by the arc melting equipment usually has a distribution in length. For example, when scrap is used as an iron source, ordinary scrap is a mixed state of various brands of scrap. As a typical scrap with a maximum length of 1200 mm, considering the scrap composed of metal shredder, steel cutting scraps, wheel scraps, Dalai powder, etc., the distribution of the ratio of the length to the maximum length is the maximum length as an example. Those with a length less than 25% are 44 mass%, 25% or more, less than 50% are 24 mass%, 50% or more, less than 75% are 18 mass%, 75% or more, 100% or less It is about 14 mass% and has some variation. If the size of the iron source is within the range of such a normal variation, it is suitable for carrying out the present invention using the maximum length A.

  When the maximum length A of the iron source is changed after the arc melting furnace is installed, in order to adjust the shaft front dimension, the upper part of the front part of the boundary between the preheating chamber and the melting chamber (X in FIG. 1) It is also possible to adjust the shaft front dimension from H to H ′ by exchanging the parts of FIG. Since the arc melting equipment 1 is not usually manufactured as a single unit and is a combination of a plurality of parts, adjustment using such a frontage adjusting part 12 is also possible. Or the method of processing and changing the size of an iron source according to a shaft front dimension can be used with respect to the size change of an iron source.

  The above principle will be described with reference to FIG. FIG. 4 is a graph qualitatively showing the relationship between the operating time (1 / productivity) of the arc melting equipment and the shaft opening dimension H in the present embodiment. As shown in FIG. 4, the smaller the shaft opening dimension H, the less smooth the supply of the iron source to the melting chamber, so the melting time required for the melting period takes longer. The larger the shaft opening dimension H, the easier the iron source supply. The dissolution time is short. On the other hand, the temperature rise time in the temperature raising period is shorter because the smaller the shaft opening dimension H, the more the iron source does not roll into the molten metal, and the longer the temperature rise time, the longer the longer the time, the longer the iron source flows into the molten metal. For this reason, as the shaft opening dimension H increases, the range of the optimum shaft opening dimension H in which the operation time is the shortest as a result of canceling out the change in both the decreasing melting time and the increasing temperature rising time. Will exist.

  As a result of various studies, the present inventors have found that the optimum value is obtained when the shaft opening dimension H is within a range satisfying the relationship of A ≦ H ≦ 4A with respect to the maximum length A of the iron source 5. It was.

  Further, in the arc melting equipment of the present embodiment, at least a part of the bottom surface 7 of the continuous bottom surface 7 of the melting chamber 2 and the preheating chamber 4 is formed as an inclined bottom surface 7a, and the inclination angle of the inclined bottom surface 7a is horizontal. The angle is preferably 15 to 45 degrees with respect to the direction. When the angle of the inclined bottom surface 7a is gentle (when the angle with respect to the horizontal direction is small), it is difficult to efficiently supply the iron source in the direction of the melting chamber, and the operation time in the melting period becomes long. Accordingly, the inclination angle of the inclined bottom surface 7a is preferably set to 15 degrees or more. On the other hand, when the angle of the inclined bottom surface 7a at the lower part of the preheating chamber 4 is steep, the iron source can easily move to the melting chamber, and the iron source can be smoothly supplied toward the electrode of the melting chamber. If it becomes too much, even if the operation of the extrusion device is stopped, the iron source may collapse. Therefore, the inclination angle of the inclined bottom surface 7a is preferably set to 45 degrees or less.

  The above principle will be described with reference to FIG. FIG. 5 is a graph qualitatively showing the relationship between the operation time (1 / productivity) of the arc melting equipment and the inclined bottom surface angle in the present embodiment. As shown in FIG. 5, the melting time required for the melting period takes longer as the tilted bottom surface angle is smaller, and the larger the time, the easier the supply of the iron source becomes. On the other hand, the temperature raising time in the temperature raising period is shorter as the tilted bottom surface angle is smaller, and the larger the time is, the longer it takes to flow and collapse of the iron source into the molten metal. From this, when operating the arc melting facility of the present embodiment, as shown in FIG. 5, both the decreasing melting time and the increasing temperature rising time with the increase in the angle of the inclined bottom surface angle. As a result of the offsetting of the change, there will be an optimum tilted bottom angle that will minimize the operating time.

  As a result of various studies, the present inventors have determined that the inclination angle of the inclined bottom surface is horizontal in a furnace in which the shaft opening dimension H satisfies the relationship of A ≦ H ≦ 4A with respect to the maximum length A as described above. The range of 15 to 45 degrees with respect to the direction is preferable for shortening the operation time, and particularly when the inclination angle is 25 to 35 degrees, the length of the iron source satisfying the relationship of A ≦ H ≦ 4A It has been found that the collapsing prevention effect is high and preferable even when the distribution is larger.

  The above results are summarized in Table 1.

In Table 1, θ is the inclination angle of the inclined bottom surface, and the on / off switching control performance of the iron source supply from the preheating chamber to the melting chamber when the inclination angle θ and the shaft opening dimension H are respectively changed. Specifically, the smoothness of the supply of the iron source from the preheating chamber to the melting chamber, and the state of the occurrence of a flow or collapse of the iron source into the molten metal in the melting chamber during the temperature rising period are shown. × △ ○ ◎ indicates the smoothness of the supply of iron source from the preheating chamber to the melting chamber and the level of prevention of the occurrence of iron source inflow and collapse. × indicates the supply of iron source from the preheating chamber to the melting chamber. In the case of stagnation without progressing smoothly or when the iron source flows into the molten metal or collapses, the supply of the iron source smoothly flows into the molten metal in the order of △ ○ ◎.・ The level of prevention of collapse is improved.

As shown in Table 1, the optimum value is within the range where the shaft front dimension H is A ≦ H ≦ 4A, and within this range, the supply of the iron source from the preheating chamber to the melting chamber in the melting phase is smooth. In the temperature rising period, the supply of the iron source from the preheating chamber to the melting chamber is stopped. However, even within the range of A ≦ H ≦ 4A, when the tilt angle (θ) of the tilted bottom surface is more than 45 degrees with respect to the horizontal direction, the iron source is in a state of being easily collapsed, on the other hand, less than 15 degrees However, depending on the state of the iron source, there may be cases where the supply to the melting chamber cannot be performed smoothly. Therefore, if the inclination angle (θ) of the inclined bottom surface is 15 degrees or more and 45 degrees or less, it is most preferable because it is possible to sufficiently prevent the iron source from flowing and collapsing and to smoothly supply the iron source. Furthermore, the shortest distance L (distance between X and electrode 3a) between the highest portion (X in FIG. 1), which is the highest position among the connecting portions of the preheating chamber and the melting chamber, and the electrode 3 is the maximum of the iron source. It is preferable that the relationship of 0.2A ≦ L ≦ 5A is satisfied with respect to the length A. If the distance L between the shaft front end and the electrode is too short, electrode breakage is likely to occur when the iron source is supplied. When the electrode breakage occurs as described above, it is necessary to stop the operation and replace the electrode, so that productivity is lowered. Moreover, when an iron source exists under an electrode, arc efficiency will also fall. For this reason, L is preferably 0.2 A or more. Note that if the distance L between the frontage and the electrode is too long, the distance between the electrode and the iron source is increased and the arc efficiency is lowered. Therefore, L is preferably 5 A or less.

  The above principle will be described with reference to FIG. FIG. 6 is a graph showing the relationship between the electrode breakage occurrence frequency and the shortest distance L (distance between X and electrode 3a) when operating the arc melting equipment in this embodiment, that is, iron source charging The change of the electrode breakage occurrence frequency by the distance L between the frontage and the electrode is shown. As shown in FIG. 6, the frequency of electrode breakage increases rapidly when L is less than 0.2A, and decreases as it is longer than A. Therefore, L is preferably 0.2A or more. I understand. In addition, as shown in FIG. 6, when H = 4A, the electrode breakage occurrence frequency is 0.5 times / month or less and the occurrence frequency is low, as shown in FIG. On the other hand, when H = 4A in the case of H> 4A, it can be seen that the frequency of electrode breakage increases to 10 times / month or more even if L is 0.2A or more. From this, it is understood that the shaft opening dimension H is preferably set within a range satisfying the relationship of H ≦ 4A with respect to the maximum length A of the iron source 5 from the viewpoint of preventing the occurrence of electrode breakage. . In addition, as shown in FIG. 6, if H is too large with respect to A, even if L is increased, the frequency of occurrence of electrode breakage increases to 10 times / month or more, and the power efficiency when arc-dissolving scrap is lowered. I understand that.

  From the above, in the present embodiment, the shortest distance L between the highest portion X and the electrode 3a, which is the highest position in the connection portion between the preheating chamber and the melting chamber, is relative to the length A of the longest side of the iron source. By setting so as to satisfy the relationship of 0.2A ≦ L ≦ 5A, it is possible to suppress the occurrence of electrode breakage and the decrease in arc efficiency when supplying the iron source.

  Next, the manufacturing method of the molten metal using the above arc melting equipment is demonstrated using FIG.

  In this operation method, the exhaust gas generated in the melting chamber 2 is introduced into the preheating chamber 4 to preheat the iron source 5 in the preheating chamber 4, and the extrusion disposed under the preheating chamber 4 for preheating the iron source 5. The step of supplying the iron source 5 from the preheating chamber 4 to the melting chamber 2 by driving the apparatus 6 and the iron source 5 in the melting chamber 2 so as to keep the iron source 5 in the preheating chamber 4 and the melting chamber 2. And a step of melting the iron source 5 by arc heating in the melting chamber 2 to supply the molten metal 9 while supplying and a step of raising the temperature of the molten metal 9 by stopping the driving of the extrusion device 6. To do. Thereby, metal melts, such as molten steel, can be manufactured using an iron source.

  A test for melting molten steel by melting scrap was conducted in an apparatus having a furnace capacity of about 200 tons similar to the arc melting equipment shown in FIGS.

  It was decided to use iron scrap scraps treated to a maximum length of 1200 mm or less as the scrap (maximum length A = 1200 mm).

  (Comparative example) The shaft opening dimension H of the arc melting equipment was 5000 mm (4A <H), and the angle from the horizontal direction of the inclined bottom surface of the lower part of the preheating chamber was 30 degrees. The shortest distance L between the highest portion, which is the highest position among the connecting portions between the preheating chamber and the melting chamber, and the electrode was about 2.5 m.

  Scrap was charged into the preheating chamber a plurality of times, and during the melting period, the extruder was driven to continuously supply the scrap to the melting chamber. Since the predetermined amount of scrap was charged into the shaft, the drive of the extrusion device was stopped. The drive of the extrusion device was turned on / off using a control device. The elapsed time at this time was about 40 minutes, and the integrated input power amount was about 40 MWh. When the driving of the extrusion device is stopped, the supply of scrap into the melting chamber is not completely stopped, and a small amount of scrap continues to flow into the melting chamber, and the temperature of the molten steel is increased to about 1650 ° C. for 10 minutes. Cost. The amount of power used at this time was 10 MWh.

  (Example of the present invention) Next, a front opening adjusting part (not shown) installed in the upper part of the front part of the arc melting equipment (part X in FIG. 1) is replaced, and the shaft front dimension H is set to a shaft opening dimension of A ≦ H ≦ 4A It adjusted to 3000 mm used as one numerical value within the range.

  When scrap was melted in the same manner as described above, the amount of molten steel in the melting chamber reached a predetermined value after 40 MWh for 40 minutes, so the drive of the extrusion device was stopped. Then, the supply of the scrap to the melting chamber was stopped, and the time for raising the temperature of the molten steel to about 1650 ° C. was 5 minutes, and the power consumption at this time was 5 MWh.

  In the above embodiment, by setting the shaft opening dimension H within the range of the present invention, it becomes possible to control the supply of scrap from the preheating chamber to the melting chamber, and as a result of improving the temperature raising efficiency, the productivity is also improved by 10%. . That is, when the shaft opening dimension H is set to H = 5000 mm, which is outside the range of the optimum value of the shaft opening dimension H of the present invention, the scrap is completely supplied to the melting chamber even if the driving of the extrusion device is stopped. However, the thermal efficiency during the temperature rise of the molten steel was not good. On the other hand, when the shaft opening dimension H is set to a value within the range of the optimum value of the shaft opening dimension H of the present invention and H = 3000 mm, and the driving of the extrusion device is stopped, scrap melting The supply to the chamber was completely stopped, and the thermal efficiency was improved when the molten steel was heated.

  Initially, assuming the maximum scrap length A = 500 mm, the shaft opening dimension H is 700 mm, and the scrap capacity is melted by melting the scrap in the same furnace as the arc melting equipment shown in Figs. The test which manufactures was conducted.

  Thereafter, the scrap to be processed was changed, and operation was started with a maximum scrap length A of 1000 mm. In this case, the shaft opening dimension H is in a relationship of H <A with respect to the maximum scrap length A, and it was expected that the scrap could not be smoothly charged into the melting chamber. The frontage adjustment component 12 to be constructed was replaced, the shaft frontage dimension H was changed to 1500 mm, and operation using scrap with a maximum length A of 1000 mm was performed. This allowed stable operation.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

DESCRIPTION OF SYMBOLS 1 Arc melting equipment 2 Melting chamber 3 Electrode 3a Furnace top side electrode 3b Furnace bottom electrode 4 Preheating chamber 5 Iron source 6 Extruding device 7 Bottom surface of melting chamber 7a Inclined bottom surface 8 Furnace lid 9 Molten metal 10 Outlet port 11 Exhaust port 12 Front port Adjustment part H Shaft front dimension L Shortest distance between X and electrode P Vertical Q Arrow indicating preheating chamber side R Arrow indicating melting chamber side X Highest part

Claims (8)

A melting chamber for melting the iron source, a shaft-type preheating chamber provided directly connected to the melting chamber so that the iron source is preheated before being supplied to the melting chamber, and the preheating chamber. An arc melting facility comprising an electrode provided in the melting chamber for melting the iron source,
At least a part of the bottom surface of the preheating chamber continuous with the bottom surface of the melting chamber is formed as an inclined bottom surface having a downward slope toward the melting chamber,
The shaft opening dimension H, which is the shortest distance in the arc melting facility between the highest position of the connecting portion between the preheating chamber and the melting chamber and the continuous bottom surface of the melting chamber and the preheating chamber, Set to the optimum value for iron source supply control,
An extrusion device that moves the iron source supplied from the preheating chamber in the direction of the melting chamber is provided at a lower portion of the preheating chamber. When the extrusion device is driven, the iron source is moved from the preheating chamber into the melting chamber. Is supplied,
When the driving of the extrusion device is stopped, the supply of the iron source from the preheating chamber to the melting chamber is stopped. The optimum value of the shaft opening dimension H is the maximum length A of the iron source,
2. The arc melting equipment according to claim 1, wherein the arc melting equipment is set so as to satisfy a relationship of A ≦ H ≦ 4A.   The arc melting equipment according to claim 1, wherein an inclination angle of the inclined bottom surface is 15 to 45 degrees with respect to a horizontal direction. A melting chamber for melting the iron source, a shaft-type preheating chamber provided directly connected to the melting chamber so that the iron source is preheated before being supplied to the melting chamber, and the preheating chamber. An arc melting facility comprising an electrode provided in the melting chamber for melting the iron source,
At least a part of the bottom surface of the preheating chamber continuous with the bottom surface of the melting chamber is formed as an inclined bottom surface having a downward slope of 15 to 45 degrees with respect to the horizontal direction toward the melting chamber,
The shaft opening dimension H, which is the shortest distance in the arc melting facility between the highest position of the connecting portion between the preheating chamber and the melting chamber and the continuous bottom surface of the melting chamber and the preheating chamber, For the maximum length A of the iron source,
It is set to satisfy the relationship of A ≦ H ≦ 4A,
An arc melting facility characterized in that an extrusion device for moving the iron source supplied from the preheating chamber in the direction of the melting chamber is provided below the preheating chamber.   5. The shaft opening dimension can be changed by configuring the upper part of the connection portion between the melting chamber and the preheating chamber from replaceable parts. 6. Arc melting equipment as described in the paragraph. The shortest distance L between the highest position among the connecting portions of the preheating chamber and the melting chamber and the electrode is relative to the maximum length A of the iron source.
The arc melting equipment according to any one of claims 1 to 4, wherein a relation of 0.2A≤L≤5A is satisfied. The shortest distance L between the highest position among the connecting portions of the preheating chamber and the melting chamber and the electrode is relative to the maximum length A of the iron source.
The arc melting equipment according to claim 5, wherein a relation of 0.2A ≦ L ≦ 5A is satisfied. A method for producing a molten metal using the arc melting equipment according to any one of claims 1 to 7,
Introducing the exhaust gas generated in the melting chamber into the preheating chamber to preheat the iron source in the preheating chamber;
Supplying the iron source from the preheating chamber to the melting chamber by driving the extrusion device disposed under the preheating chamber for preheating the iron source;
A step of melting the iron source by arc heating in the melting chamber while supplying the iron source to the melting chamber so as to keep the iron source in the preheating chamber and the melting chamber. When,
Stopping the driving of the extrusion device and raising the temperature of the molten metal;
The manufacturing method of the molten metal using the arc melting equipment characterized by including this.

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