JP2009120960A - Screw for ejecting reduced iron in rotary hearth furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw for ejecting reduced iron in a rotary hearth furnace excellent in durability. <P>SOLUTION: In the screw 4 for ejecting the reduced iron in the rotary hearth furnace 1, composed of circularly arranged with spiral blades 42 on the outer circumferential surface of a rotation shaft 41 cooled in the inner part by passing through cooling water and ejecting the reduced iron on this furnace hearth 3 to the outer side of the furnace body 2 from the ejecting hole 3a arranged at the outer circumferential side of the rotating furnace hearth 3; a refractory layer 43 is formed on the outer circumferential surface of the rotating shaft 41. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention particularly relates to a rotary hearth furnace that produces reduced iron by reducing a reduced iron raw material mainly composed of a carbon-based reducing material and iron oxide. Belongs to the technical field of reduced iron discharge screw of a rotary hearth furnace to be discharged out of the rotary hearth furnace.

As is well known, for example, a rotary hearth furnace is used to produce reduced iron by reducing a reduced iron raw material mainly composed of a carbon-based reducing material and iron oxide.
In such a rotary hearth furnace, the reduced iron on the hearth is discharged out of the rotary hearth furnace from an outlet provided on the outer peripheral side of the hearth rotating around the vertical axis, that is, on the high speed side. It has a reduced iron discharge screw. The durability of this reduced iron discharge screw is extremely important for improving the operating rate of the rotary hearth furnace, that is, improving the productivity of reduced iron. Means have been proposed.

  For example, in Patent Document 1 (conventional example 1), a cooling water passage is provided inside a screw shaft that is a rotating shaft, and the temperature is lowered by passing cooling water through the cooling water passage to ensure the strength of the screw shaft. By improving the durability of the screw shaft, a hollow portion is formed in the screw blade that is a spiral blade, and the temperature of the screw blade is decreased by passing cooling water through the hollow portion to ensure the hardness of the screw blade. Describes a reduced iron discharge screw that improves the wear resistance of the screw blades.

  Further, in Patent Document 2 (Conventional Example 2), similarly to Patent Document 1, a cooling water channel is provided inside a screw shaft that is a rotating shaft of the reduced iron discharge screw, and the cooling water flow into this cooling water channel is provided. In addition to improving the durability of the screw shaft by lowering the temperature with the screw, the screw blades, which are spiral blades, of the blade blades that are particularly severely worn are combined together, A reduced iron discharge screw is described in which the life of the screw blade is extended by increasing the thickness. In order to further improve the wear resistance of the tip portion of the screw blade, an inconel alloy (55% nickel, 55% nickel) is provided on both side surfaces of the screw blade tip portion as described in paragraph [0013]. 45% chromium) is built up by welding.

  By the way, even if the strength of the screw shaft of the reduced iron discharge screw is improved and the life of the screw blade is extended by improving the wear resistance of the screw blade or increasing the wear allowance, the reduced iron discharge screw will eventually rotate. It is necessary to carry out maintenance work by removing the iron from the hearth furnace and repairing it, and incorporating the reduced iron discharge screw into the rotary hearth furnace after the repair. The maintenance work of such reduced iron discharge screw is performed after the operation of the rotary hearth furnace is stopped and the inside of the rotary hearth furnace is lowered to a workable temperature. It is described in paragraph number [0008] of Patent Document 2 according to Example 2. This is because the reduced iron discharge screw is disconnected from the tethering facility and coupling, and then repaired by removing it from the top through the furnace roof of the rotary hearth furnace and incorporating it into the rotary hearth furnace from above after the repair. It is.

US Pat. No. 4,636,127 Japanese Patent Laid-Open No. 10-339583

  In the reduced iron discharge screw according to the above-described conventional example, the corrosive gas generated from the reduced iron raw material is aggregated on the shaft surface of the screw shaft and the blade surface of the screw blade, the temperature of which is lowered by the flow of cooling water. Accordingly, the shaft surfaces of these screw shafts and the blade surfaces of the screw blades are corroded at a low temperature by the agglomerated corrosive gas. Even when iron ore is reduced, SOX is generated due to sulfur contained in the coal mixed in the raw material pellets as a reducing material, and this SOX causes the shaft surface of the screw shaft and the blades of the screw blades. The surface is corroded and their life is reduced as in the case of reduced iron raw materials.

  Incidentally, according to the description in Patent Document 2, the service life until the coolant leakage of the screw shaft using carbon steel occurs is 4 to 10 months, and the life of the screw blade is about 5 months. In other words, neither of these screw shafts and screw blades can be said to be sufficient with respect to the endurance life, and maintenance work of the reduced iron discharge screw must be performed frequently. It cannot be improved. In addition, the screw blade is covered with a hardened layer formed by welding Inconel alloy by welding on the tip surface and both side surfaces of the tip portion. Welding defects such as undercuts are likely to occur in between, and the screw blades are lost due to the notch effect, and even if the other parts are fully usable, maintenance may occur. There is also.

  In the case of a reduced iron discharge screw, the screw blades of the spiral blade, which are particularly worn parts, are combined together and the life of the screw blade is extended by increasing the thickness. Since the blades are formed in a three-dimensional shape, it is difficult to manufacture two screw blades with high accuracy, and an increase in the cost of the reduced iron discharge screw cannot be avoided.

  In addition, for maintenance work of the reduced iron discharge screw, the furnace roof must be removed at least as much as the projected area of the reduced iron discharge screw, and since the opening of the furnace body roof is large, a large measure of heat protection is required. Furthermore, due to the layout of the equipment, equipment such as raw material bottles are often placed above the reduced iron discharge screw, and depending on the relationship between the facilities, it takes a lot of time to remove the reduced iron discharge screw. There was a problem to be solved that required labor.

  Accordingly, an object of the present invention is to provide a reduced iron discharge screw for a rotary hearth furnace excellent in durability.

  The present invention has been made in view of the above circumstances, and the means adopted by the reduced iron discharge screw of the rotary hearth furnace according to claim 1 of the present invention is internally cooled by the flow of cooling water. A rotary hearth furnace that has spiral blades on the outer circumferential surface of the rotating shaft and discharges the reduced iron on the hearth to the outside of the furnace body from a discharge port provided on the outer circumferential side of the rotating hearth. In the reduced iron discharge screw, a refractory layer is formed on the outer peripheral surface of the rotating shaft.

  In the reduced iron discharge screw of the rotary hearth furnace according to claim 1, the means adopted by the reduced iron discharge screw of the rotary hearth furnace according to claim 2 of the present invention is the tip of the spiral blade, A long groove having a width smaller than the thickness width of the spiral blade is provided, and the long groove is filled with a hardfacing layer.

  The means adopted by the reduced iron discharge screw of the rotary hearth furnace according to claim 3 of the present invention is the reduced iron discharge screw of the rotary hearth furnace according to any one of claims 1 and 2. The number of strips on the outer peripheral side of the hearth of the spiral blade is greater than the number of strips on the inner peripheral side of the hearth.

  The means adopted by the reduced iron discharge screw of the rotary hearth furnace according to claim 4 of the present invention is the reduced iron of the rotary hearth furnace according to any one of claims 1, 2, or 3. The discharge screw is characterized in that the shaft end portion of the rotating shaft is supported by a support device via a buffer member so as to be lifted and held at a predetermined height.

  According to the reduced iron discharge screw of the rotary hearth furnace according to claim 1 of the present invention, the refractory layer is formed on the outer peripheral surface of the rotating shaft of the reduced iron discharge screw, and the temperature of the refractory layer is In addition to being maintained at a temperature higher than the temperature of the outer peripheral surface of the rotating shaft that continues to be cooled with water during operation, the aggregation of corrosive gas is suppressed, and even if corrosive gas is aggregated, Since the contact of the corrosive gas with the outer peripheral surface is prevented, the progress of the corrosion of the rotating shaft is suppressed, and the life of the rotating shaft can be significantly extended.

  According to the reduced iron discharge screw of the rotary hearth furnace according to claim 2 of the present invention, the long groove provided in the front end surface of the reduced iron discharge screw 4 spiral blade is embedded by the hardfacing layer, and the front end portion As in the case of a conventional screw blade covered with a hardfacing layer on both sides, there is a welding defect such as an undercut that occurs between the base material on the side of the tip of the screw blade and the built-up portion. Since it does not occur, there is an effect that the loss of the spiral blade due to the welding defect can be prevented.

  According to the reduced iron discharge screw of the rotary hearth furnace according to claim 3 of the present invention, the number of strips on the outer peripheral side of the hearth of the spiral blade is larger than the number of strips on the inner peripheral side of the hearth. The reduced iron moving at high speed on the upper surface on the outer periphery side of the hearth can be moved in the direction of the discharge port without passing through the spiral blade, and the reduced iron discharge screw can be rotated at a low speed. Since the wear of the spiral blade is reduced, there is an effect that the life of the spiral blade is greatly extended as compared with the conventional example.

  According to the reduced iron discharge screw of the rotary hearth furnace according to claim 4 of the present invention, the reduced iron discharge screw is supported via the buffer member, and the axis of the reduced iron discharge screw and the surface of the hearth Even if the distance between the two is slightly changed, the contact pressure of the tip of the spiral blade of the reduced iron discharge screw to the hearth surface is kept below a predetermined contact pressure. Can greatly contribute.

  Furthermore, according to the reduced iron discharge screw of the rotary hearth furnace according to claims 1 to 4 of the present invention, the effect of preventing the corrosion of the rotating shaft due to the corrosive gas by the formation of the refractory layer on the outer peripheral surface, the tip of the spiral blade Defect prevention effect by embedding in the hard cladding layer of the long groove of the surface, the effect of suppressing the wear of the spiral blade by reducing the rotation speed by increasing the number of spiral blades on the discharge port side, the tip surface of the spiral blade by supporting the buffer member As a result of the synergistic effect with the effect of preventing the increase in contact pressure on the hearth surface, the life of the reduced iron discharge screw is greatly extended compared to the conventional example, and the reduced iron discharge screw is less frequently repaired. The operating rate of the floor furnace is greatly improved, and it is possible to achieve an extremely excellent effect that it can greatly contribute to the cost reduction of the reduced iron.

It is sectional drawing explanatory drawing in the reduced iron discharge screw arrangement | positioning position of a rotary hearth furnace in connection with embodiment of this invention. FIG. 2 is a detailed view of part A in FIG. 1. It is the B section detailed drawing of FIG. FIG. 2 is a detailed view of part C in FIG. 1. It is sectional drawing of the rotating shaft of a reduced iron discharge screw concerning embodiment of this invention. It is sectional drawing of a spiral blade in connection with embodiment of this invention. It is a side surface explanatory drawing of a reduced iron discharge screw concerning the Example of this invention.

  Hereinafter, the rotary hearth furnace and the reduced iron discharge screw of the rotary hearth furnace according to the embodiment of the present invention are shown in FIG. FIG. 2 is a detailed view of part A in FIG. 1, FIG. 3 is a detailed view of part B of FIG. 1, FIG. 4 is a detailed view of part C of FIG. This will be described with reference to FIG. 6 showing a cross-sectional view of the spiral blade and FIG. 7 showing a side view of the reduced iron discharge screw.

  Reference numeral 1 shown in FIG. 1 is a rotary hearth furnace, and a furnace main body 2 of the rotary hearth furnace 1 is formed of a hearth 3 that rotates around a vertical rotation center (not shown) on the left side in FIG. There is provided a reduced iron discharge screw 4 having a configuration to be described later for discharging the reduced iron on the discharge port 3a provided on the outer peripheral side on the right side of the hearth 3. Each of the ends of the rotating shaft 41 of the reduced iron discharge screw 4 is provided on both side walls of the heat insulating housing 2a that constitutes a part of the furnace body 2 that covers the upper side of the hearth 3, and the reduced iron discharge screw 4 The spiral blade 42 is inserted into the through hole 2b which is set to a dimension that allows the spiral blade 42 to pass through in a loosely fitted state. An inner bearing 5 in which a greasing pipe 51 is connected to the shaft end on the inner peripheral side of the hearth 3 of the rotary shaft 41 and an outer bearing in which a greasing pipe 51 is connected to the shaft end on the outer peripheral side. 5 'is externally fitted.

  As shown in FIG. 2, the inner bearing 5 is moved up and down by a hydraulically actuated inner support device 7 via cushioning members 6 made of an elastic member such as a rubber sheet on the upper surface and the lower surface of the mounting flange of the inner bearing 5. Is supported to be. Of course, the outer bearing 5 ′ is also supported by the hydraulically operated outer support device 7 ′ via a buffer member (not shown), like the inner bearing 5. By the way, the inner / outer support devices 7 and 7 'are provided to keep the distance between the axis of the reduced iron discharge screw 4 and the hearth 3 constant, and the buffer member 6 Even if, for example, the surface of the hearth 3 has irregularities (cannot be completely eliminated) and the distance between the axis of the reduced iron discharge screw 4 and the surface of the hearth 3 is slightly changed, this reduction This is provided to keep the contact pressure of the tip surface of the spiral blade 42 of the iron discharge screw 4 to the surface of the hearth 3 below a predetermined contact pressure.

  Since the inner / outer support devices 7 and 7 'are hydraulically operated as described above, when the contact pressure of the tip surface of the spiral blade 42 is about to exceed the predetermined contact pressure, the reduced iron discharge The screw 4 can be configured to escape upward. By configuring the support devices 7 and 7 'as described above, there is an effect that it is possible to prevent the reduced iron discharge screw 4 and the hearth 3 from being damaged due to the biting of large foreign matters.

Each of the through holes 2b and 2b is closed by inner and outer closing members 8 and 9 which are detachably mounted on the shaft end of the rotating shaft 41 and have a configuration which will be described later.
That is, as shown in FIG. 3, the inner lid member 8 on the left side in FIG. 1, that is, the inner peripheral side of the hearth 3 is detachably fixed to the side wall of the heat insulating housing 2a to close the through hole 2b. A seal cover 81 integrally formed by a flange member to be fitted and a cylindrical member fitted on the rotary shaft 41, and a tubular member fitted on the side wall side of the inner bearing 5, that is, on the outside of the seal cover 81. And a seal flange 82 having an oil chamber 82a for storing oil supplied from the grease supply pipe 82b.

  Further, as shown in FIG. 4, the outer cover member 9 on the outer peripheral side of the hearth 3 is detachably fixed to the side wall of the heat insulating housing 2a to close the through hole 2b, and a rotating shaft. A seal cover 91 integrally formed with a cylindrical member fitted on the outer periphery 41, and is fitted on the outer side of the seal cover 91 on the side wall side of the outer bearing 5 'so as to be fixed to the cylindrical member. The seal flange 92 includes an oil chamber 92a for storing oil supplied from the oil pipe 92b. That is, the outer lid member 9 has substantially the same configuration as the inner lid member 8. Further, the rotary hearth furnace 1 incorporates the reduced iron discharge screw 4 removed and repaired into the furnace body 2 when the reduced iron discharge screw 4 is removed from the furnace body 2 of the rotary hearth furnace 1. An inner screw support device 10 and an outer screw support device 20 that will be described later are used.

As shown in FIGS. 1 and 3, the inner screw support device 10 is disposed at an outer position on the inner peripheral side of the hearth 3, and the inner screw support device 10 is placed on a gantry on a predetermined basis. Is guided by a height-adjustable guide roller 14 provided at a predetermined distance, and reciprocally moves to a tip on the inner peripheral side of the hearth 3 of the rotary shaft 41 from which the end plate 41b is removed. Is provided with a rod-shaped screw support fitting 11 which is detachably connected by attaching and detaching bolts. The screw support fitting 11 is used to pull out the reduced iron discharge screw 4 from the furnace body 2 and to insert the reduced iron discharge screw 4 that has been removed and repaired into the furnace body 2. It serves to support the tip on the inner peripheral side of the hearth 3. Further, an inner winch 12 that is a metal pulling means for pulling the screw support metal 11 and moving it to the outer side on the inner peripheral side of the hearth 3 by winding the metal pulling rope 13 is provided.
Note that a cooling water passage is provided inside the screw support fitting 11, and the cooling water passage is configured to allow water cooling by passing the cooling water through the cooling water passage.

As shown in FIG. 1, the outer screw support device 20 is disposed at an outer position on the outer peripheral side of the hearth 3, and the outer screw support device 10 is a guide laid on a gantry. A screw support carriage 21 is provided which is guided by the rail 24 and reciprocates to support the tip of the reduced iron discharge screw 4 on the inner peripheral side of the hearth 3.
Further, by pulling the reduced iron discharge screw 4 by winding the screw pulling rope 23 and pulling the reduced iron discharge screw 4 from the furnace body 2 by pulling the reduced iron discharge screw 4 to the outer side on the outer peripheral side of the hearth 3. An outer winch 22 as a means is provided.

  As can be understood from the above description, according to the inner screw support device 10 and the outer screw support device 20, when the reduced iron discharge screw 4 is removed from the furnace body 2, the tip of the screw support fitting 11 is discharged from the reduced iron. It connects with the front-end | tip part of the inner peripheral side of the hearth 3 of the rotating shaft 41 of the screw 4. Then, by connecting the screw tow rope 23 to the tip of the outer peripheral side of the hearth 3, winding the screw tow rope 23 by driving the outer winch 22, and feeding the metal tow rope 13 from the inner winch 12, The reduced iron discharge screw 4 can be extracted from the furnace body 2 in the outward direction on the outer peripheral side of the hearth 3.

  On the other hand, contrary to the above, the metal tow rope 13 is wound up by driving the inner winch 12 and the screw tow rope 23 is fed out by the outer winch 22, thereby reducing the reduced iron discharge screw 4 to the inner periphery of the hearth 3. It can be moved sideways and incorporated into the furnace body 2.

  Next, the detailed configuration of the reduced iron discharge screw 4 will be described with reference to FIG. 1 and FIGS. 5 to 7. A swivel joint 4a formed in an elbow shape is provided at the outer peripheral side end of the hearth 3 of the rotating shaft 41 of the reduced iron discharge screw 4, and a cooling water inflow pipe 4b connected to the swivel joint 4a. The cooling water is supplied to a cooling water passage 41a (see FIG. 5) formed in the rotary shaft 41. Needless to say, the cooling water that has become high temperature by cooling the rotating shaft 41 of the reduced iron discharge screw 4 is drained from a cooling water drain pipe 4c connected to the swivel joint 4a.

  A refractory layer 43 is formed on the outer peripheral surface of the rotating shaft 41 of the reduced iron discharge screw 4 as shown in FIG. As described above, the refractory layer 43 is formed on the outer peripheral surface of the rotating shaft 41. This prevents corrosion of the rotating shaft 41 by preventing the corrosive gas from contacting the outer peripheral surface of the rotating shaft 41. It is what I aimed for. By the way, since the temperature of the refractory layer 43 is kept higher than the temperature of the outer peripheral surface of the rotating shaft 41 which is continuously cooled with water during operation, an effect of suppressing the aggregation of corrosive gas occurs.

  Further, as shown in FIG. 6, a long groove 45 having a width smaller than the thickness width of the spiral blade 42 is provided on the front end surface of the spiral blade 42 of the reduced iron discharge screw 4, and the long groove 45 has a hardened wall. It is embedded by the raised layer 46. As the hardfacing material used for the hardfacing layer 46, an Fe-based material obtained by eutectic chromium carbide on austenitic stainless steel was used. As a result, the undercut generated between the base material on the side surface of the tip of the screw blade and the built-up portion, like the screw blade according to the conventional example in which the tip portion and both side surfaces are covered with the hardfacing layer. It is possible to prevent the build-up portion from being lost due to such a welding defect.

  By the way, in this Embodiment, since the hardfacing layer is not formed in the side surface of the front-end | tip part of the spiral blade 42 as above-mentioned, it is thought that the side surface of the front-end | tip part of this spiral blade 42 wears out early. It is done. However, according to the inventors' long experience, it has been found that although the tip surface of the spiral blade 42 is abraded violently, the side surface of the tip is not so worn. Nevertheless, the tip and both side surfaces of the screw blade according to the conventional example are covered with the hardfacing layer, and when the hardfacing layer is formed only on the tip surface, it is hardened by the shearing force generated during rotation. It can be understood that this is because the overlay layer may be peeled off from the tip surface.

Further, the number of spiral blades on the outer peripheral side of the hearth 3 of the reduced iron discharge screw 4, that is, on the discharge port 3 a side, is larger than the number of spiral blades on the inner peripheral side of the hearth 3.
More specifically, as shown in FIG. 7, the entire length of the spiral blade 42 is the outer peripheral surface on the discharge port 3 a side of the rotating shaft 41 of the reduced iron discharge screw 4 and between the spiral pitches of the spiral blade 42. The intermediate spiral blade (the end face is shown in FIG. 7 is painted out) 44 having a length of 周 is provided. Of course, a long groove having a width smaller than the wall thickness of the intermediate spiral blade 44 is provided on the front end surface of the intermediate spiral blade 44 in the same manner as the spiral blade 42, and the long groove is embedded by the hardfacing layer. Yes. The reduced iron discharge screw 4 is configured as described above because the reduced iron on the hearth 3 can be moved in the direction of the discharge port 3a without passing through the spiral blade, and the reduced iron discharge screw 4 This is to reduce the wear of the spiral blade 42 and the intermediate spiral blade 44 by rotating 4 at a low speed.

  As is well known, the circumferential speed of the hearth 3 gradually increases as it goes toward the outer periphery of the hearth 3, so the relative speed when the spiral blade 42 and the hearth 3 are in contact with each other is higher in the hearth 3. Become fast. Further, when discharging the reduced iron on the upper surface of the hearth 3 to the outside of the furnace body 2, in order to surely move the reduced iron in the direction of the discharge port 3 a while preventing slipping from the spiral blade 42, It is necessary to rotate the reduced iron discharge screw 4 at a rotation speed sufficient to capture the reduced iron moving at a high speed, that is, the reduced iron located on the uppermost surface of the hearth 3. Accordingly, the reduced iron discharge screw 4 is rotated at a high speed, and the spiral blade 42 is worn in a short time, so that the reduced iron discharge screw 4 has to be short-lived. Therefore, as described above, even if the reduced iron discharge screw 4 is rotated at a low speed by providing the intermediate spiral blade 44, the reduced iron can be reliably moved in the direction of the discharge port 3a while preventing slipping through. This is because the life of the spiral blade can be extended.

  By the way, as described above, the length of the intermediate spiral blade 44 is set to be 1/3 of the total length of the spiral blade 42. However, the length is not particularly limited to 1/3 of the total length of the spiral blade 42. The length of the intermediate spiral blade 44 may be appropriately determined according to the relative speed between the spiral blade and the surface of the hearth 3. Even if the total length of the intermediate spiral blade 44 is the same as the total length of the spiral blade 42 and the intermediate spiral blade 44 is positioned between the entire spiral pitches of the spiral blade 42, the reduced iron discharge having the above-described configuration is possible. The effect of reducing the wear of the spiral blade equivalent to that of the screw 4 can be obtained. However, since the circumferential speed on the inner circumferential side of the hearth 3 is lower than the circumferential speed on the outer circumferential side and the spiral blade 42 is sufficient, the intermediate spiral blade 44 is provided. This is not preferable because it is over-spec and disadvantageous with respect to the manufacturing cost of the reduced iron discharge screw 4.

Hereinafter, the operation modes of the rotary hearth furnace 1 and the reduced iron discharge screw 4 configured as described above will be described. First, an operation mode of the rotary hearth furnace 1 will be described. A chain and a sprocket 41d are connected to a hearth 3 and a drive device 1a provided on the furnace body 2 while the rotary hearth furnace 1 is in operation. The reduced iron discharge screw 4 is rotated.
When the reduced iron discharge screw 4 gradually wears due to the continuous rotation and the wear amount reaches a predetermined amount, the reduced iron discharge screw 4 is removed from the heat insulating housing 2a of the furnace body 2 for repair. However, prior to the extraction work, a preparatory work for extracting the reduced iron discharge screw 4 is performed.

  The greasing pipe 51 is removed from the inner bearing 5 that supports the inner peripheral end of the hearth 3 of the reduced iron discharge screw 4, and the greasing pipe 2 b is removed from the seal flange 82 of the inner lid member 8. And from the edge part of the inner peripheral side of the hearth 3 of the rotating shaft 41 of the reduced iron discharge screw 4, the end plate 41b which positions the reduced iron discharge screw 4 in the longitudinal direction, the spacer 41c, the inner support device 7 The inner bearing 5 removed from the inner wall 5 is removed, and the inner cover member 8 including the seal cover 81 and the seal flange 82 is removed from the heat insulating housing 2a, so that the inner peripheral end of the hearth 3 of the rotary shaft 41 is brought into a free state. To do.

  Then, by utilizing the screw hole to which the end plate 41b is attached, the tip of the screw support fitting 11 of the inner screw support device 10 is connected to the inner peripheral end surface of the hearth 3 of the rotating shaft 41. The end on the inner peripheral side of the rotating shaft 41 is held at a predetermined height by the guide rollers 14 and 14, and a cooling water supply and a cooling water drain pipe (not shown) are connected to the screw support fitting 11.

  Next, the greasing pipe 51 is removed from the outer bearing 5 ′ supporting the outer peripheral end of the hearth 3 of the reduced iron discharge screw 4, and the greasing pipe 92 b is removed from the seal flange 92 of the outer lid member 9, The outer bearing 5 'is removed from the outer support device 7'. Then, the outer cover member 9 including the seal cover 91 and the seal flange 92 is removed from the heat insulation housing 2a, the chain is removed from the sprocket 41d, and the outer peripheral end of the hearth 3 of the rotating shaft 41 is set in a free state. Thus, the preparatory work for extracting the reduced iron discharge screw 4 from the furnace body 2 is completed. By removing the inner lid member 8 and the outer lid member 9 in such a preparatory work, the reduced iron discharge screw 4 can be extracted through the through holes 2b and 2b.

  When the preparatory work as described above is finished, the work of extracting the reduced iron discharge screw 4 from the furnace body 2 is performed. That is, the screw pulling rope at the outer winch 22 of the outer screw support device 20 while the outer end of the hearth 3 of the rotary shaft 41 in the free state is suspended by a hook F via a wire rope (not shown). 23 is wound and the reduced iron discharge screw 4 is extracted through the through holes 2b and 2b of the heat insulating housing 2a. The extracted reduced iron discharge screw 4 is placed on the screw support carriage 21, and the screw support carriage 21 on which the reduced iron discharge screw 4 is placed is moved to a predetermined repair work place on the gantry of the outer screw support device 20. By moving it, the extraction operation of the reduced iron discharge screw 4 is completed. When extracting the reduced iron discharge screw 4 from the furnace body 2, in order to reduce the damage of the reduced iron discharge screw 4 when passing through the furnace body 2, a simple heat insulation work is performed to reduce the reduced iron discharge screw 4. It is preferable to protect.

Thereafter, repair work of the reduced iron discharge screw 4 is performed, and this time, the metal winch 12 that is drawn out when the reduced iron discharge screw 4 is pulled out by the inner winch 12 of the inner screw support device 10 is wound up, and the heat insulating housing The parts on the outer peripheral side of the hearth 3 and the parts on the inner peripheral side of the hearth 3 which are assembled through the through holes 2b and 2b of 2a and removed by the reverse procedure to the above are attached to appropriate portions.
Then, the screw support fitting 11 is detached from the inner peripheral end of the hearth 3 of the rotary shaft 41, and the screw support fitting 11 is removed from the hearth 3 of the rotary shaft 41 by further winding the metal pulling rope 13 by the inner winch 12. After retracting in the direction away from the end on the inner peripheral side, the end plate 41b, the spacer 41c, and the inner bearing 5 are attached, the greasing pipe 51 is attached to the inner bearing 5, and the seal flange 82 of the inner closing member 8 is attached. The restoration work is completed by attaching the greasing pipes 82b to each.

  Therefore, according to the rotary hearth furnace 1 according to the present embodiment, it is not necessary to remove the portion corresponding to the projected area of the reduced iron discharge screw of the furnace body roof as in the conventional example, and the through holes 2b, Since the opening area of 2b is smaller than the projected area of the reduced iron discharge screw, it is not necessary to take a large heat-resistant measure. Furthermore, because of the layout of the equipment, even if equipment such as a raw material bottle is arranged at the upper position, the reduced iron discharge screw 4 is pulled out in the horizontal direction and incorporated from the horizontal direction. In any case, the reduced iron discharge screw 4 can be removed from the furnace body 2 and the reduced iron discharge screw 4 can be incorporated into the furnace body 2 in a much shorter time and with less effort than the conventional example. There is a great effect that the maintenance cost of the iron discharge screw 4 can be greatly reduced.

  Next, the operation mode of the reduced iron discharge screw 4 of the rotary hearth furnace according to the present embodiment will be described. In the reduced iron discharge screw 4, a refractory layer 43 is formed on the outer peripheral surface of the rotary shaft 41. In addition, the temperature of the refractory layer 43 is kept higher than the temperature of the outer peripheral surface of the rotary shaft 41 that is continuously cooled with water during operation, and in addition to suppressing aggregation of corrosive gas, for example, corrosion. Even if the coherent gas is aggregated, the corrosive gas is prevented from coming into contact with the outer peripheral surface of the rotary shaft 41, and therefore the progress of corrosion of the rotary shaft 41 is effectively suppressed.

  Moreover, the long groove 45 provided in the front end surface of the spiral blade 42 of this reduced iron discharge screw 4 is embedded by the hardfacing layer 46, and the conventional example in which the front end portion and both side surfaces are covered by the hardfacing layer. Like this screw blade, there is no occurrence of a welding defect such as an undercut that occurs between the base material on the side surface of the tip portion of the screw blade and the built-up portion, and the loss of the spiral blade due to the welding defect is prevented. Is done.

  Further, an intermediate spiral which is the outer peripheral surface of the rotary shaft 41 of the reduced iron discharge screw 4 on the discharge port 3a side and is 1/3 of the total length of the spiral blade 42 during the spiral pitch of the spiral blade 42. Since the blades 44 are provided around, the reduced iron on the upper surface of the hearth 3 can be moved in the direction of the discharge port 3a without passing through the spiral blades, and the reduced iron discharge screw 4 is rotated at a low speed. Therefore, the wear of the spiral blade 42 and the intermediate spiral blade 44 is reduced, and the life of the spiral blade 42 and the intermediate spiral blade 44 is greatly extended as compared with the conventional example. Furthermore, the bearing that is externally fitted to the reduced iron discharge screw 4 is supported via the buffer member 6, and the distance between the axis of the reduced iron discharge screw 4 and the surface of the hearth 3 has changed somewhat. Even so, since the contact pressure of the tip surface of the spiral blade 42 of the reduced iron discharge screw 4 to the surface of the hearth 3 is maintained below a predetermined contact pressure, it can greatly contribute to the suppression of wear of the spiral blade. .

  Therefore, according to the reduced iron discharge screw 4 of the rotary hearth furnace according to the embodiment of the present invention, the corrosion prevention effect of the rotary shaft 41 by the corrosive gas due to the formation of the refractory layer 43 on the outer peripheral surface, the spiral blade 42 The effect of preventing the loss by embedding the long groove 45 provided in the hardfacing layer 46 in the front end surface of the outer peripheral surface of the rotary shaft 41, the outer peripheral surface on the discharge port 3 a side, and the intermediate spiral between the spiral pitches of the spiral blades 42 Due to the synergistic effect of the effect of suppressing the wear of the spiral blade by reducing the number of rotations due to the circumferential arrangement of the blade 44, and the effect of preventing the increase in the contact pressure of the tip surface of the spiral blade 42 to the surface of the hearth 3 by the support of the buffer member 6, The life of the reduced iron discharge screw 4 is greatly extended as compared with the conventional example, and the repair frequency of the reduced iron discharge screw 4 is reduced. As a result, the operating rate of the rotary hearth furnace 1 can be greatly improved, and an extremely excellent effect that it can greatly contribute to cost reduction of reduced iron can be achieved. It should be noted that the life of the reduced iron discharge screw 4 can be extended as such even if any one of the above measures is taken for the reduced iron discharge screw 4.

  DESCRIPTION OF SYMBOLS 1 ... Rotary hearth furnace, 1a ... Drive apparatus, 2 ... Furnace main body, 2a ... Thermal insulation housing, 2b ... Through-hole, 3 ... Hearth, 3a ... Discharge port, 4 ... Reduced iron discharge screw, 4a ... Swivel joint, 4b ... cooling water inflow pipe, 4b ... cooling water drain pipe, 41 ... rotating shaft, 41a ... cooling water passage, 41b ... end plate, 41c ... spacer, 41d ... sprocket, 42 ... spiral blade, 43 ... refractory layer, 44 ... Intermediate spiral blade, 45 ... long groove, 46 ... hardened layer, 5 ... inner bearing, 5 '... outer bearing, 51 ... grease pipe, 6 ... buffer member, 7 ... inner support device, 7' ... outer support device, 8 ... Inner cover member, 81 ... Seal cover, 82 ... Seal flange, 82a ... Oil and fat chamber, 82b ... Grease supply pipe, 9 ... Outer cover member, 91 ... Seal cover, 92 ... Seal flange, 92a ... Oil and fat chamber, 92b ... greasing piping, 10 Inner screw support device, 11 ... Screw support fitting, 12 ... Inner winch, 13 ... Metal pulling rope, 14 ... Guide roller, 20 ... Outer screw support device, 21 ... Screw support carriage, 22 ... Outer winch, 23 ... Screw pulling rope , 24 ... guide rails.

Claims (4)

  Spiral blades are provided around the outer peripheral surface of the rotating shaft, the inside of which is cooled by the flow of cooling water, and the reduced iron on the hearth is supplied from the discharge port provided on the outer peripheral side of the rotating hearth. A reduced iron discharge screw for a rotary hearth furnace, wherein a refractory layer is formed on an outer peripheral surface of the rotary shaft in the reduced iron discharge screw of the rotary hearth furnace to be discharged to the outside.   2. The rotary hearth furnace according to claim 1, wherein a long groove having a width smaller than a thickness width of the spiral blade is provided on a front end surface of the spiral blade, and the long groove is filled with a hardfacing layer. Reduced iron discharge screw.   The number of strips on the outer peripheral side of the hearth of the spiral blades is larger than the number of strips on the inner peripheral side of the hearth, according to any one of claims 1 and 2. Reduced iron discharge screw for rotary hearth furnace.   The shaft end of the rotating shaft is supported by a support device via a buffer member so as to be lifted and held at a predetermined height. The reduced iron discharge screw of the rotary hearth furnace as described in the item.

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