JP4378432B2 - Hot air circulation furnace - Google Patents

Description

  The present invention relates to a hot air circulating furnace for circulating hot air to heat a workpiece to a predetermined heat treatment temperature. More specifically, the present invention relates to a hot air circulating furnace suitable for heat treatment of a material that is relatively difficult to take a thermal head, such as T6 heat treatment of an aluminum alloy.

  Conventionally, as a hot air circulation type heat treatment furnace that heats a workpiece with hot air forcedly circulated by a fan, there is one shown in FIG. 9 (Japanese Patent Laid-Open No. 2002-173708). In this fast heating furnace, a cylindrical work storage chamber 3 having upper and lower openings is coaxially arranged in a furnace chamber 2 made of a refractory material, and hot air generated by a burner B installed at the bottom of the furnace is circulated. The work W is heated at high speed by forcibly convection as a vortex by a fan (sirocco fan) 4. Circulation such that hot air flows into the workpiece storage chamber 3 from the bottom of the workpiece storage chamber 3 and is discharged by the circulation fan 4 into the circulation passage 5 between the workpiece storage chamber 3 and the surrounding refractory wall 21 and descends. Are provided. A circulation passage through which hot air is circulated uniformly over the entire circumference between the furnace chamber 2 and the workpiece storage chamber 3 by providing a door 7 at the second workpiece transfer port 35 of the workpiece storage chamber 3 and closing the door 7. To ensure. The work W is put into and out of the furnace by opening the door D of the first work transfer port 22 and the door 7 of the work storage chamber 3 in the furnace chamber 2, and heat treatment is batch processing. It is.

  Moreover, as a continuous processing furnace, although not shown, a tunnel-type long processing furnace is generally used, and a predetermined temperature is maintained while a work carried in from a work carry-in port at one end moves toward a work carry-out port at the other end. To be heated up to.

JP 2002-173708 A

  However, since the high-speed heating furnace of FIG. 9 is a batch process, a large amount of hot air in the furnace flows out and cold air outside the furnace flows in and cools the interior of the furnace chamber 2 each time workpieces are loaded and unloaded. Therefore, there is a problem that the thermal efficiency is poor and the processing time is excessive.

  In addition, the circulation fan 4 used in the high-speed heating furnace is a sirocco fan and has a structure in which the blades are exposed. There is a problem that cannot be heated. The sirocco fan determines the air volume depending on the design of the surrounding casing, and the air volume is not obtained unless the blade is exposed and the casing is not present. Therefore, even if a sirocco fan with an exposed blade is installed, static pressure cannot be recovered, and only circulating air around the fan does not cause a circulating flow throughout the furnace. Further, even if a casing is provided so that the air volume can be obtained, the circulating flow of hot air becomes a vortex, so that the circulation flow is biased and cannot be uniformly contacted with the workpiece, so that uneven heating tends to occur. There's a problem. Furthermore, since the work is arranged in the center and the circulation passage is provided in the periphery, there is a problem that the dead space increases, the amount of work that can be processed for the furnace body volume is small, and the heating efficiency is poor.

  In addition, because it is heated by hot air circulating in a vortex, the furnace interior cannot be divided into a heating zone and a soaking zone, so it takes time to raise the temperature, and in particular, a thermal head such as an aluminum alloy can be made large. In the case of a work that cannot be performed, the effect is large. For example, the heat treatment of an aluminum alloy is performed by quenching (solution treatment) at a temperature close to the melting point (softening point) of aluminum, so the thermal head cannot be made large, and only depends on heating by convective heat transfer. In other words, if the thermal head of the furnace temperature and the object to be heated is made larger, the temperature rise time can be shortened. However, in the case of an aluminum heat treatment furnace, the melting or deformation of the object to be heated is different from that of a general heat treatment furnace. The thermal head cannot be made large because there is a risk of this. If the thermal head is small, the ratio of heating by radiant heat transfer decreases and the ratio of heating by convective heat transfer increases. In general, in the T6 treatment in the middle temperature region of about 500 ° C., the heat transfer amount when the basket is used is about 85% for convective heat transfer and about 15% for radiant heat transfer. Thus, since heating by radiant heat transfer is limited by the presence of the critical furnace temperature, the temperature rise of the workpiece inevitably depends on heating by convective heat transfer. As is well known, the heating capacity by convective heat transfer is determined as a function of the flow rate and flow rate of the heating fluid, so that proper design of the hot air circulation fan in the furnace is very important. However, in the actual furnace design, the flow rate or flow rate of the hot air circulation fan cannot be increased without limit, and there is a limit to the installation of a large fan due to the relationship with the furnace body size.

  In the case of a tunnel-type continuous processing furnace, there is a problem that the size is increased. In particular, when it is used for heat treatment of a material such as an aluminum alloy, which is relatively difficult to take a thermal head, the furnace length tends to be long because heating takes time.

  On the other hand, production forms are constantly changing and diversifying, and not only reducing production costs with large continuous furnaces as before, but also various heat treatment facilities are required in relation to automobile models and production numbers. . For this reason, there is a demand for a high-performance dedicated industrial furnace installed in the final process of a casting line, for example, not as a single facility for a heat treatment furnace. For example, it is desirable to install a furnace with a small processing amount at the end of the casting line and eliminate the waste of heating from room temperature by heat treatment without cooling after casting. In addition, even in a forged aluminum product (heated and pressed; becomes dense), it is necessary to heat the workpiece one by one in order to perform primary heating, secondary heating, quenching, and tempering. In this case, a furnace with a small processing amount that can load, transfer, and unload workpieces one by one is desired. This applies not only to aluminum products but also to other non-ferrous metal alloys and steels. In response to such demands, a large conventional tunnel-type continuous heat treatment furnace premised on a large amount of processing cannot be easily met.

  Accordingly, an object of the present invention is to provide a hot air circulating furnace for continuous processing that is small but has a large throughput. Another object of the present invention is to provide a hot air circulating furnace capable of uniform heating. Furthermore, an object of the present invention is to provide a hot air circulation furnace capable of configuring a heating zone and a soaking zone.

  In order to achieve this object, a hot air circulating furnace according to the first aspect of the present invention includes a furnace body including a heat source and a rotary hearth, and a peripheral wall of the rotary furnace floor along a peripheral wall of the furnace body. And a work-placeable shelf comprising a work-placement shelf made of a breathable material or structure in which the work can be carried in and out in the radial direction and the circulating flow of hot gas can pass vertically. An annular work mounting table, and the furnace body is divided into an outer peripheral side region where the work mounting table is installed and an inner side region inside thereof, and in the vicinity of the rotary hearth and the ceiling An annular partition provided with upper and lower passages for communicating the inner side region and the outer peripheral side region respectively, and hot gas received near the ceiling of the furnace body from the outer periphery of the fan to the central portion Before inhaling An axial flow fan that discharges toward the rotary hearth through the inner region that is the inner side of the annular partition, and the hot gas is discharged to the inner region by the axial fan, The inside is radially discharged to the outer peripheral side region outside the annular partition through the lower passage near the rotary hearth along the annular partition, and passes through the workpiece mounting shelf of the workpiece mounting table. A circulation flow is formed which rises and is heated again by the heat source and then sucked into the axial fan.

  An axial fan has the property of sucking the atmosphere around the periphery without much stirring and blowing it out in the axial direction (furnace bottom direction), and can circulate in almost the same place. Accordingly, the hot air supplied from the heat source is discharged to the space in the center of the furnace by the axial fan, flows out of the inside of the annular partition along the annular partition to the outside of the annular partition through the passage near the rotary hearth, and the workpiece mounting table. The circulating flow that rises through the workpiece mounting shelf and is heated again by the heat source or mixed with the hot air supplied from the heat source and heated, and then sucked into the axial fan, that is, from the inside to the outside of the furnace body A circulating flow is formed radially throughout the furnace. And if the atmosphere in a furnace carries out a fixed circulation, it becomes possible to supply the output of a specific burner to a specific zone. For example, a plurality of zones such as a heating zone and a soaking zone are provided, each provided with a burner, and the output can be controlled separately according to the temperature of each zone. As a result, the amount of heat required for each zone, for example, the heating zone where the temperature drop due to newly added workpieces is markedly reduced and the soaking zone where the temperature drop is low, are separately supplied and supplied to the heating zone and soaking zone respectively. The hot gas can be supplied at the same temperature or by setting a desired temperature difference.

  According to a second aspect of the present invention, in the hot air circulating furnace according to the first aspect, the work mounting table has a plurality of work mounting shelves. In this case, since the workpieces on the workpiece mounting shelf can be heated one after another by the rising hot air, a large amount of processing can be performed.

  The invention described in claim 3 is the hot air circulating furnace according to claim 1 or 2, wherein the work mounting table is circumferentially divided by a partition that is divided in the circumferential direction for each space on which the work to be processed is placed. And communicated in the vertical direction via a work mounting shelf. In this case, since the hot air flow path for each work vertical line is secured by the partition, the circulating flow formed by the axial fan can be circulated in substantially the same place without being disturbed by contact with the work.

  Furthermore, the invention described in claim 4 is the hot air circulating furnace according to any one of claims 1 to 3, wherein the loading / unloading port enables loading / unloading of a work for each work placing shelf at each stage of the work placing table. In addition, an extraction port is provided on the peripheral wall of the furnace body. In this case, since only the space in which the necessary work is stored can be opened and the work can be taken out, heat loss generated during the work loading or extraction is reduced.

  Further, the invention according to claim 5 is the hot air circulating furnace according to claim 4, wherein the inlet and the extraction port each have a door that opens and closes independently, and a workpiece is placed between the inlet and the extraction port. An interval in which at least one work storage space for the table exists is set. In this case, since the work storage space communicating with the outside of the furnace at the time of workpiece extraction (removal) and workpiece loading is limited to the work storage space facing the loading inlet and the extraction port, excess heat does not escape. Even if the loading port and the extraction port are opened simultaneously, there is no direct communication between the loading port and the extraction port because there is at least one workpiece storage space between them.

  As is clear from the above description, according to the hot air circulating furnace according to the invention of claim 1, since the axial fan can be installed using the center of the furnace that becomes the dead area, the space in the furnace can be effectively utilized, The furnace becomes compact without creating wasted space. In addition, since the annular workpiece mounting table is disposed on the outer peripheral portion of the rotary hearth, the longest workpiece mounting shelf can be configured, so that a large amount of workpieces can be processed for the installation area of the furnace.

  Also, the radial circulation of hot gas by the axial fan circulates almost the same place without much stirring of the atmosphere around the fan, so that the output of a specific burner can be supplied to a specific zone. If a thermistor and a burner are provided in the soaking zone and the burner output is controlled separately according to the temperature of each zone, the necessary amount of heat can be supplied only in the heating zone. As a result, the temperature drop in the soaking zone does not occur due to the newly input work, and the necessary amount of heat can be supplied only in the heating zone. In addition, the axial flow fan (which discharges along the shaft) can be heated evenly even if there is no casing around it.

  Furthermore, according to the rotary hearth-type hot air circulation furnace according to the second aspect of the present invention, the number of workpieces that can be simultaneously processed by the number of workpiece mounting shelves can be increased, thereby enabling a large amount of processing.

  Further, according to the rotary hearth type hot air circulation furnace according to the invention of claim 3, since the hot air flow path for each longitudinal column of the work is secured, the circulating flow formed by the axial fan is also brought into contact with the work. It is possible to circulate almost the same place without being disturbed. For this reason, zone separation is further facilitated even with a single axial fan.

  Further, according to the rotary hearth type hot air circulation furnace according to the invention described in claim 4, since only the space in which the necessary work is stored can be opened and the work can be taken out, the heat generated during the work loading or extraction. Loss is reduced.

  Further, according to the rotary hearth type hot air circulating furnace according to the invention described in claim 5, the work storage space that communicates with the outside of the furnace when the work is taken out and when the work is loaded is a work storage space that faces the charging inlet and the extraction port. Because it is limited, excess heat does not escape. Even if the loading port and the extraction port are opened simultaneously, there is no direct communication between the loading port and the extraction port because there is at least one workpiece storage space between them.

It is a principle figure which shows one Embodiment of the hot air circulation furnace of this invention, and is a front view. It is a side view of the same hot air circulation furnace. It is a top view of the same hot air circulation furnace. It is a perspective view of the hot air circulation furnace. It is a center longitudinal cross-sectional view which shows one Example which applied the hot-air circulation furnace of this invention to the T6 heat processing furnace of aluminum. It is a cross-sectional view of the T6 heat treatment furnace. It is a top view of the T6 heat treatment furnace. It is a front view of the T6 heat treatment furnace. It is a top view of the conventional heat processing furnace.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  1 to 4 show an embodiment of the hot air circulation furnace of the present invention. In this hot-air circulating furnace, the hearth 2 part of the furnace body 1 is constituted by a turntable, and an object to be heated (not shown; referred to as a work in this specification) is placed on a work placing table 23 installed on the turntable. This is a continuous heating furnace in which predetermined heating is completed during one rotation of the hearth 2 and the furnace floor 2 can be sequentially taken out.

  The furnace body 1 includes a cylindrical peripheral wall (furnace wall) 3 made of a refractory and heat-resistant material, a ceiling 4, and a hearth 2 that can be separated and rotated. A heat source 5 is provided outside the peripheral wall 3. . The peripheral wall 3 and the ceiling 4 surrounding the rotary hearth 2 are installed and fixed to a support structure material (not shown) of the furnace.

  The inside of the furnace is partitioned by an annular partition 8 and separated into an outer peripheral side region 6 where the workpiece mounting table 23 is installed and an inner side region 7 inside thereof. The annular partition 8 is provided not to completely partition the entire area from the hearth 2 to the ceiling 4 but to provide upper and lower passages 9 and 10 in which the circulation flow is reversed in the vicinity of the rotary hearth 2 and the ceiling 4. It has been. That is, the inside of the furnace separated into the inner region 7 and the outer region 6 by the annular partition 8 is communicated by the lower passage (opening) 9 near the hearth and the upper passage (opening) 10 near the ceiling, and the shaft It is provided so that gas can circulate between the outer peripheral side region 6 and the inner side region 7 by driving the flow fan 11.

  The axial fan 11 is provided in the center of the furnace body near the ceiling 4 toward the hearth 2, and sucks and discharges hot gas from the fan outer peripheral direction toward the center direction toward the hearth 2, thereby A circulation flow that flows radially from the inside to the outside of the furnace body is formed in the entire region of the furnace body from the region 7 → the lower passage 9 → the outer peripheral side region 6 → the upper passage 10 → the inner side region 7. The axial fan 11 has a characteristic that it sucks the outer atmosphere without much stirring and blows it in the axial direction, that is, in the direction of the hearth 2 in this embodiment. Furthermore, a rectifying effect is further enhanced by attaching guides to the suction side and the discharge side of the fan. Due to this characteristic, the atmosphere in the furnace can be circulated in almost the same place. Therefore, the zone can be separated by providing an appropriate guide or partition for even one axial fan. Although not shown, the axial fan drive source is preferably arranged outside the furnace body 1 and the rotation shaft of the fan arranged in the furnace is protruded from the ceiling 4 to the outside of the furnace so that the chain, sprocket, etc. It is made to rotate by interposing.

Therefore, a partition may be provided in the inner region 7 inside the annular partition 8 to make zone separation more reliable as necessary. In the case of this embodiment, a partition 12 having a narrower opening on the outlet side than the inlet side into which the circulating flow flows is attached. In this case, the outlet opening angle θ _{2 in the} vicinity of the hearth 4 is narrowed with respect to the inlet opening angle θ ₁ in the vicinity of the ceiling of the inward region 7 defined by the partition 12, and the decrease in the opening area is reduced. As a result, the flow velocity of the circulating gas is increased, and a part of the high-temperature gas discharged from the axial fan 11 can be supplied to the workpiece mounting table 23 at a higher wind speed. In addition, it is not necessary to change the wind speed (heating state) of the circulating flow throughout the furnace, but when there is a need for clearer zone separation, the inlet opening angle θ ₁ and the outlet opening angle θ ₂ are the same angle. A partition (not shown in the figure) that is partitioned straight is used. In this case, the amount of hot air discharged from the axial fan is uniform, and an amount corresponding to the entrance-side opening area of the partition is introduced and discharged from the exit-side opening that is narrower than the entrance-side opening area. For this reason, the speed of the hot air is increased by an amount corresponding to the reduction in the opening area on the outlet side, and the hot air is discharged from under the work mounting table, and rises through the work mounting shelf. In other words, a part of the hot air can form a region where the circulation flow is faster in some regions than the other regions. Therefore, in heating mainly using convection heat transfer, a circulating gas of the same temperature is used to equalize the heating zone. Can form the tropics.

  In the dead space at the center of the furnace, a cylindrical body 14 that fills the space is arranged to prevent the flow from being disturbed.

  In the case of this embodiment, the annular partition 8 is suspended from the ceiling 4 by using the cover 13 of the axial fan 11 installed on the ceiling 4. That is, the annular partition 8 is suspended from the cover 13 that covers the bearing portion of the ceiling 4 that supports the rotating shaft of the axial fan 11 via, for example, three plate-like stays 15. Further, a radial partition 12 arranged in the radial direction is attached to the inside of the annular partition 8, and a cylindrical body 14 is attached to the ceiling 4 via the partition 12 so as to fill a dead space at the center of the furnace. It is suspended. The annular partition 8, the partition 12, and the cylindrical body 14 are fixed to the furnace body 1 through a cover 13 that is joined to each other by welding, riveting, or the like and integrally attached to the ceiling 4. However, since the cylindrical body 14 and the annular partition 8 are arranged coaxially with the center of rotation of the hearth 2, the zone separation partition 12 that is required to be in a fixed position regardless of the rotation of the hearth 2 In contrast, it is not always attached to and supported by a fixed furnace body side, for example, the ceiling 4 or the like. That is, in some cases, the cylindrical body 14 and the annular partition 8 may be installed so as to stand on the hearth 2.

  The hearth 2 is provided with a reversing portion 28 which is formed in an annular shape between the outer peripheral side region 6 and the inner side region 7 so as to smoothly reverse the hot air descending upward and convert it into an upward flow. In this embodiment, the inversion part 28 is formed by a semicircular recess having a cross-sectional shape. Here, the inversion part 28 of the hearth 2 is formed in an area where the peripheral part and the central part of the hearth 2 are left in consideration of the installation of the work table 23 and the position where the circulating flow flows. The outer edge of the reversing unit 28 is positioned at the approximate center of the workpiece mounting table 23, and the inner edge is formed so as to be positioned near the cylindrical body 14 filling the dead space at the center of the hearth 2. The hot air rises from approximately the center of 23. The inversion part 28 can also be formed by providing the cylindrical body 14 with a skirt that warps in a semicircular shape. In this case, it is sufficient to provide a simple-shaped recess having a uniform depth except for the outer peripheral edge of the hearth 2 for the refractory and heat-resistant material constituting the hearth 2. Becomes easy. The skirt portion is formed of, for example, the same material as that of the cylindrical body 14 and integrated by welding or the like, and is also installed on the hearth 2 together with the cylindrical body 14.

  An annular workpiece mounting table 23 is provided along the peripheral wall 3 on the rotary hearth 2 in the outer peripheral region 6. The workpiece mounting table 23 includes a workpiece mounting shelf 24 on which a workpiece can be loaded and unloaded in a radial direction and a circulating flow can pass in the vertical direction. The work mounting shelf 24 is preferably provided in a plurality of stages, and a processing amount can be ensured. Moreover, it is preferable to provide the partition 25 in the workpiece | work mounting base 23 in order to ensure the hot-air flow path for every workpiece | work vertical line. In the case of the present embodiment, the partition 25 is disposed in the radial direction, and the work mounting table 23 is partitioned in the circumferential direction to create the work accommodation space 22. Here, since the partition of the zone does not cause a leak, it is sufficient to install a thin iron plate in a groove / slit from the hearth 2 to the ceiling 4. In this case, the partition 25 Supports free expansion and contraction as possible. For example, by inserting a partition 25 made of a steel plate into a vertically extending grooved steel or a vertically opening slit disposed on the inside and outside of the workpiece mounting table 23, the workpiece is supported so as to be stretchable. . In addition, the workpiece mounting table 23, the annular partition 8, the zone separation partition 12, the cylindrical body 14 and the like disposed in the furnace are made of an appropriate material according to the temperature and composition of the circulating hot gas, for example, heat-resistant steel. It goes without saying that it is done.

  In addition, each work placement shelf 24 is made of a breathable material or structure that allows smooth flow of hot air. For example, it is preferable to use a bar material or a mesh or punching metal that is disposed with a gap in the radial direction, the circumferential direction, or both. Further, in some cases, both ends of the inner and outer ends of the workpiece may be supported by a frame material that forms the outer and inner peripheral edges of the workpiece mounting shelf 24. That is, the work mounting shelf 24 may be configured by only a double ring of the outer ring and the inner ring. If such a work mounting shelf that can support a work without a basket is used, the amount of heat for heating the basket becomes unnecessary, and the fuel consumption rate can be improved and the work temperature raising time can be shortened. Also, the production cost and maintenance cost of the basket are not required.

  Although not shown, the peripheral wall 1 of the furnace body is provided with a loading port 20 and an extraction port 21 that allow workpieces to be taken in and out. In the case of the present embodiment, the loading port 20 and the extraction port 21 that enable the workpiece to be taken out are provided for each workpiece mounting shelf 24 of each stage of the workpiece mounting table 23. As shown in FIG. 3, the loading port 20 and the extraction port 21 have doors 26 and 27 that open and close independently, and the work storage space of the work mounting table 23 is between the loading port 20 and the extraction port 21. It is preferable that an interval in which at least one 22 exists is set, but in some cases, the intervals may be adjacent to each other without leaving a space. In some cases, the loading port 20 and the extraction port 21 may be shared and provided in one place, and further, a door for each individual work mounting shelf 24 may be provided in one door. . Even if the loading port 20 and the extraction port 21 are arranged at a distance narrower than the gap of the workpiece storage space 22 without providing at least one workpiece storage space 22, a partition 25 exists between the two ports 20 and 21. In this case, the loading port 20 and the extraction port 21 are separated to some extent.

  A burner is preferably used as the heat source 5, but a radiant tube, an electric heater, or the like may be used depending on circumstances. When the burner is used, it is disposed outside the peripheral wall of the furnace body, and is installed so as to inject combustion gas in a substantially tangential direction with respect to the axial fan disposed in the center of the furnace body. Here, when the circulating flow generated in the furnace is separated into a plurality of zones, it is preferable to arrange a burner 5 as a heat source for each zone so that the output can be controlled independently. In this case, it becomes possible to supply the output of a specific burner to a specific zone in combination with the constant circulation of the atmosphere in the furnace, set the temperature for each zone, or set the temperature for each zone It is also possible to supply a necessary amount of heat so that a temperature difference between zones does not occur.

  A temperature sensor such as a thermistor is installed in the heating zone 17 and the soaking zone 16, and the heat source 5 is provided so that the temperature of the circulating gas immediately before being supplied to the workpiece mounting table 23 in the outer peripheral region 6 becomes the set temperature. It is controlled.

  According to the hot air circulation furnace configured as described above, the hot air supplied from the heat source 5 is discharged by the axial fan 11 to the space / inside region 7 in the center of the furnace, and the inside of the annular partition 8 is surrounded by the annular partition 8. Along the lower passage 9 near the rotary hearth 2, flows out to the outer peripheral side region 6 outside the annular partition 8, rises while passing through the work mounting shelf 24 of the work mounting table 23, and again enters the furnace After being heated by the heat source 5 near the ceiling 4 or mixed with hot air supplied from the heat source 5 and heated up, it is sucked into the axial fan 11 and discharged to the inner side region 7 again. That is, the in-furnace atmosphere circulated by the axial fan 11 circulates between the inner region 7 and the outer region 6 in substantially the same radial direction as viewed from above.

  Accordingly, the zones can be separated, and the output of a specific burner can be supplied to a specific zone. Further, this zone separation can be made more strict by arranging an appropriate guide on the discharge side or suction side of the axial fan 11. Therefore, for example, by providing the partition 12 inside the annular partition 8 or arranging a guide on the suction side of the axial fan 11 (not shown), the circulating flow supplied from one axial fan 11 A plurality of independent zones can be formed. For example, a plurality of zones such as a heating zone 17 and a soaking zone 16 are provided, each provided with a burner 5, and the output can be controlled separately according to the temperature of each zone 16, 17. As a result, the amount of heat required for each of the zones 16 and 17 is supplied separately, for example, in the heating zone 17 where the temperature drop due to the newly added workpiece is significant and the soaking zone 17 where the temperature drop is small. The hot gas supplied to the soaking zone 16 can be supplied at the same temperature or by setting a desired temperature difference.

At this time, the amount of hot air discharged from the axial fan 11 is uniform, and an amount corresponding to the opening area of the entrance side of the partition 12 is introduced. Therefore, different from the inlet opening angle theta ₁ and the outlet opening angle theta _2, the case of using an inlet opening angle theta partition 12 illustrated that is narrowed so that the outlet opening angle theta ₂ becomes narrower as compared with _1, outlet The hot air speed is increased by an amount corresponding to the reduction in the side opening area, and the hot air is discharged from under the work mounting table 23. That is, since a part of the hot air can form a region where the circulation flow is faster in some regions than the other regions, the same temperature is used in a heating temperature region where convective heat transfer is dominant, such as T6 treatment of aluminum. Even if the circulating gas is used, the heating zone and soaking zone can be formed by the difference of the flow velocity. Therefore, the heating zone 17 and the soaking zone 16 can be set without taking a thermal head. In this case, the amount of hot air discharged from the axial fan is uniform, and an amount corresponding to the entrance-side opening area of the partition is introduced and discharged from the exit-side opening that is narrower than the entrance-side opening area. For this reason, the speed of the hot air is increased by an amount corresponding to the reduction in the opening area on the outlet side, and the hot air is discharged from under the work mounting table, and rises through the work mounting shelf. In other words, a part of the hot air can form a region where the circulation flow is faster in some regions than the other regions. Therefore, in heating mainly using convection heat transfer, a circulating gas of the same temperature is used to equalize the heating zone. Can form the tropics.

  The hot air / hot gas rising through the work mounting shelf 24 heats the work. Then, the desired heat treatment is completed while the rotary hearth 2 rotates once.

  Here, the loading of the workpiece into each workpiece placement shelf 24 and the extraction of the workpiece from each workpiece placement shelf 24 are provided for each workpiece placement shelf 24 with an interval corresponding to one workpiece storage space 22. This is performed separately by the loading port 20 and the extraction port 21. In addition, the loading port 20 and the extraction port 21 are arranged so that at least one workpiece storage space 22 exists between the loading port 20 and the extraction port 21. Therefore, since the workpiece storage space 22 that communicates with the outside of the furnace when the workpiece is taken out and loaded is limited to the workpiece storage space 22 that faces the loading port 20 and the extraction port 21, excess heat does not escape. Further, even if the loading port 20 and the extraction port 21 are opened at the same time, there is no direct communication between the loading port 20 and the extraction port 21 because there is at least one work storage space 22 between them.

  5 to 8 show an example in which the hot air circulating furnace of the present invention is implemented as an aluminum T6 heat treatment furnace. In this rotary hearth type aluminum T6 heat treatment furnace, the hearth 2 of the furnace body 1 is configured on the turntable 31, and the hearth rotates once with respect to the work placed on the work mounting table 23 installed thereon. During this time, the T6 heat treatment is completed and the continuous heating furnace is made so that it can be taken out sequentially.

  The furnace body 1 includes a cylindrical furnace wall (peripheral wall) 3 made of a refractory and heat-resistant material, a ceiling 4, and a rotary hearth 2 separated from these. A gap is formed between the outer edge of the rotary hearth 2 and the inner peripheral surface of the peripheral wall 3 so that they do not contact during rotation of the rotary hearth 2, and a water seal 30 is provided in the gap portion. . The water seal 30 prevents outflow of high-temperature gas and intrusion of cold air using the water surface, and the edge of the rotary hearth 2 and the edge of the fixed peripheral wall 3 are connected to the water stored in the annular water tank. It is provided so that gas is not leaked by being immersed in each.

  The hearth 2 is rotatably supported by being placed on the turntable 31. The hearth 2 is provided with an inversion portion 28 composed of an annular recess that is lowered between the periphery and the center, and is lowered by arranging a cylindrical body 14 that fills the dead space in the center of the hearth. The incoming hot air is provided so as to be smoothly reversed along the reversing portion 28 and converted into an upward flow. Here, the outer end of the reversing portion 28 formed of a semicircular recess has a shape that rises vertically at substantially the center of the work mounting table 23 so that the hot air rises from almost directly below the work mounting table 23. Is provided.

  The turntable 31 is supported so as to be horizontally rotatable by using a thrust bearing 32 and an angular radial bearing 33 in combination. The drive mechanism 34 that rotates the turntable 31 includes a chain 35 that is fixed to the periphery of the turntable 31, a sprocket 36 that meshes with the chain 35, and a guard motor 37 that drives the sprocket 36. As a result, the rotary hearth 2 and the work mounting table 23 on the same are rotated. Since the rotary drive mechanism 34 and the workpiece transfer drive mechanism are not present in the furnace, and the mechanism for transferring workpieces is not present in the furnace, the drive is stable without being exposed to high temperatures. Since there is no need to use high-temperature components on the top, the equipment cost is also low. Here, the rotation angle of the hearth is determined by the number of work pieces in the furnace. The peripheral wall 3 surrounding the rotary hearth 2 is installed and fixed on a support structure member 38 of the furnace.

  The peripheral wall 3 of the furnace body 1 is provided with a loading port 20 and an extraction port 21 that allow loading and unloading of workpieces adjacent to each other so as to open and close independently for each stage of the workpiece mounting shelf. The loading port 20 and the extraction port 21 have doors 26 and 27 that open and close independently, and between the loading port 20 and the extraction port 21, there is at least one workpiece storage space 22 for the workpiece mounting table 23. The interval to be set is set. In order to prevent the temperature of the workpiece just before extraction due to the influence of the low-temperature workpiece, these two workpieces are adjacent to the workpiece just before the extraction whose temperature has been completed in the furnace and the low-temperature workpiece just after the next heat treatment. A work accommodating space 22 where no work exists is provided between the two. The doors 26 and 27 are pivotally attached to the furnace body / peripheral wall 3 by hinges 39 and are provided to be opened and closed by driving an actuator 40.

  Burners 5 and 5 ′ are used as heat sources, and are installed on the peripheral wall 3 of the furnace body so that the combustion gas is injected almost tangentially to the axial fan 11 disposed in the center of the furnace body. It has been. The burners 5 and 5 ′ are arranged in the heating zone 17 and the soaking zone 16, and are similarly illustrated according to the temperatures of the zones 17 and 16 detected by temperature sensors (not shown) installed in the zones. There is no controller provided to control the burner output separately.

  On the ceiling 4 of the furnace body, an in-furnace gas sucked from around by an axial fan 11 is installed so as to be discharged toward the hearth 2. The motor 41 of the axial fan 11 is installed on the outer wall surface of the peripheral wall 3 and is provided so as to drive the shaft 42 of the axial fan 11 by chain drive. Incidentally, reference numeral 43 in the figure denotes a chain cover.

  The work mounting table 23 includes a plurality of annular work mounting shelves 24 (for example, 3 to 5 stages) on which the work can be loaded and unloaded in the radial direction. It is installed along the peripheral wall 3. The work mounting shelf 24 is configured by radially arranging metal bars 44 at a constant pitch in the shape of a cage, so that a circulating flow can pass in the vertical direction.

  The inside of the furnace is separated by an annular partition into an outer peripheral side area 6 where the work placing table is installed and an inner side area 7 inside thereof, and a passage 9 in which the circulation flow is reversed near the hearth 2 and the ceiling 4. , 10 are formed.

  In the vertical direction of the work mounting table 23, a partition 25 penetrating the work mounting shelf 24 vertically is provided in order to secure a hot air flow path for each work vertical row, and an independent work storage space 22 is formed therein. The flowing hot air is provided so as not to flow into the other work accommodating space 22. Here, since the leakage does not cause a problem, the partition 25 is installed so that a thin iron plate is inserted into a groove / slit (not shown) extending in the vertical direction so as to be freely expanded and contracted. .

Inside the annular partition 8, the space between the annular partition 8 and the cylindrical body 14 is divided into a space connected to the heating zone 17 in the outer peripheral side region 6 and a space connected to the soaking zone 16 and a space connected to the heating zone 17. A partition 12 is arranged to narrow the outlet opening of the first door more than the inlet opening. This partition 12 restricts the inlet opening angle θ ₁ on the space side connected to the heating zone 17 to 180 ° and the outlet opening angle θ ₂ near the hearth 4 to 120 °, and discharges it from the axial fan 11 to the inner side region 7. The generated hot gas is divided into two, and the speed of the hot gas supplied to the heating zone 17 is supplied at a speed higher than the speed of the hot gas supplied to the soaking zone 16. Thus, a single circulation fan 11 performs heating zone 17 that requires a large amount of heat input and high-speed hot gas circulation in order to quickly raise the temperature, and hot gas circulation in soaking zone 16 that is saturated in terms of heat. Like that. The flow rate of the circulating gas is increased by the reduction of the opening area.

  In the furnace of this embodiment, the doors 26 and 27 are opened and closed by the control of the actuator 40, and the workpiece can be taken in and out by moving forward and backward straight from the loading port 20 and the extraction port 21, so that the loading of the workpiece into the furnace is possible. Input / extraction can be performed by a robot, and incidental facilities such as a charging / extraction conveyor can be omitted.

  According to the aluminum T6 heat treatment furnace configured as described above, the hot air supplied from the burners 5 and 5 ′ is discharged to the space / inside region 7 in the center of the furnace by the axial fan 11, and inside the annular partition 8. The workpiece flows out through the passage 9 near the rotary hearth 2 along the annular partition 8 to the outer peripheral side region 6 outside the annular partition 8 and passes through the workpiece placement shelf 24 of the workpiece placement table 23 while being lifted. The circulating flow that is heated and reheated by the heat sources 5 and 5 ′ or mixed with hot air supplied from the heat sources 5 and 5 ′ and heated to a set temperature and then sucked into the axial fan 11, that is, the outer periphery in the furnace A circulating flow that circulates radially between the side region 6 and the inner side region 7 is formed throughout the furnace. At this time, since the atmosphere in the furnace performs a constant circulation, the output of a specific burner is supplied to a specific zone, that is, the output of the heating zone burner 5 is set to the heating zone 17 and the output of the soaking zone burner 5 ′ is set. Supply to the soaking zone 16 is possible. Therefore, by controlling the output of the heating zone burner 5 and the soaking zone burner 5 ′ separately according to the temperature of each zone, the heating zone 17 having a significant temperature drop due to the newly added workpiece and the soaking zone 16 having a small temperature drop can be obtained. In this case, the required amount of heat is supplied separately, and the hot gas supplied to the heating zone 17 and the soaking zone 16 is supplied at the same temperature.

At this time, the amount of hot air discharged from the axial fan 11 is uniform, and an amount corresponding to the opening area of the entrance of the partition 12 for zone separation is introduced. Therefore, the amount of hot air supplied to the space connected to the soaking zone 16 and the heating zone 17 where the entrance side openings are equally divided by the partition 12 (inlet opening angle θ ₁ = 180 °) is equal. In the space connected to the heating zone 17, the opening on the exit side is narrowed (exit opening angle θ ₂ = 120 °), so that the hot air speed is increased by the amount the opening area on the exit side is narrowed. It is discharged from the bottom of the table 23. Here, in the heating temperature region where convective heat transfer is dominant as in the T6 treatment of aluminum, the temperature of the workpiece in the heating zone 17 is increased due to the difference in the flow rate even if the circulating gas of the same temperature is used. Since the speed increases as the speed increases, the heating zone 17 and the soaking zone 16 can be formed. Therefore, a heating zone and a soaking zone can be set without taking a thermal head.

  As a result, hot air can be blown to the work on the outer periphery of the hearth in an ideal flow, the heating capacity by convection heat transfer is improved, the heating time difference between the works is reduced, and the total temperature raising time can be shortened. .

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the present embodiment, the description has been mainly given of the example applied to the basketless rotary hearth type aluminum alloy heat treatment furnace, but the present invention is not limited to this, and can be applied to heat treatment of other non-ferrous alloys and heat treatment of steel. In addition, it can be carried out even when a work is put into and taken out of the basket.

DESCRIPTION OF SYMBOLS 1 Furnace 2 Hearth 3 Perimeter wall 4 Ceiling 5, 5 'Heat source 6 Outer side area 7 Inner side area 8 Annular partition 9 Lower passage 10 Upper passage 11 Axial fan 12 Zone separation partition 16 Soaking zone 17 Heating zone 20 Loading port 21 Extracting port 22 Work storage space 23 Work mounting table 24 Work mounting shelf 25 Partition

Claims (5)

A furnace body provided with a heat source and a rotary hearth, and a hot gas which is provided along a peripheral wall of the furnace body at a position near the outer peripheral side of the rotary hearth and is capable of carrying the work in and out in a radial direction. An annular work mounting table having a work mounting shelf made of a breathable material or structure that allows the circulating flow of the material to pass vertically, and the work mounting table in the furnace body. The upper and lower passages that connect the inner side region and the outer peripheral side region are provided in the vicinity of the rotary hearth and the ceiling, respectively. Annular partition and the rotary hearth through the inner side region, which is inside the annular partition, sucks hot gas that is provided near the ceiling of the furnace body and receives heat from the heat source toward the center from the outer periphery of the fan Towards The hot gas is discharged into the inner region by the axial fan, and passes through the lower passage near the rotary hearth along the annular partition inside the annular partition. Then, it flows out radially to the outer peripheral side region outside the annular partition, passes through the work mounting shelf of the work mounting table, rises, is heated again by the heat source, and then sucked into the axial fan A hot air circulating furnace characterized by forming a circulating flow. The hot air circulating furnace according to claim 1, wherein the work mounting table has a plurality of work mounting shelves. The workpiece mounting table is separated in the circumferential direction by a partition that divides in the circumferential direction for each space for loading workpieces to be processed at one time, and communicated in the vertical direction via the workpiece mounting shelf. The hot-air circulating furnace according to claim 1 or 2, wherein 4. The apparatus according to claim 1, further comprising a loading port and an extraction port on the peripheral wall of the furnace body that allow loading and unloading of the workpiece for each workpiece mounting shelf of each stage of the workpiece mounting table. The hot air circulating furnace described in 1. The loading port and the extraction port each have a door that opens and closes independently, and an interval in which at least one workpiece storage space of the workpiece mounting table exists is set between the loading port and the extraction port. The hot air circulating furnace according to claim 4, wherein

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