JP2005048264A - Continuous heat treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous heat treatment device where the intrusion of different materials into a treated material and the generation of hit mark therein can be prevented, the interruption time of operation in accordance with the change in the lot of the treated materials is reduced, and a high working ratio can be obtained. <P>SOLUTION: The continuous heat treatment device is equipped with a roller hearth type quenching furnace 2 and roller hearth type two tempering furnaces 3 and 4 (multipurpose tempering furnaces) where the object W to be heated storing a treated material 7 inside a basket 6 placed on a tray 5 is conveyed in the furnaces, and is provided with a conveying apparatus 8 conveying the object W to be heated sent out from a quenching tank 21 provided on the side of the outlet 2b in the quenching furnace 2 to an inlet 3a or 4a part of previously fixed either furnace in the two tempering furnaces. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a continuous heat treatment apparatus for tempering a processed product made of a steel material part after quenching.

For example, as a device for tempering processed products made of steel material parts such as bolts and nuts after quenching, conventionally, a mesh belt conveyor type quenching machine that stacks the processed products on a mesh belt and transports them in the furnace. It is common to use a furnace and a mesh belt conveyor type tempering furnace that is arranged in series following the quenching furnace and conveys the processed products after quenching in the furnace in the same manner as described above (for example, Patent Documents) 1 and Non-Patent Document 1).
Japanese Patent Laid-Open No. 51-28045 (page 1-2, FIGS. 1 and 3) "Industrial Furnace Handbook" edited by the Japan Industrial Furnace Association, published by Tokyo Techno Center, Inc., July 20, 1978, p. 218-219 (FIGS. 2-178,179), p. 225-226 (Figure 2-195)

  However, in the above-mentioned mesh belt conveyor type quenching furnace and tempering furnace, when the processed product is small, the processed product is caught in the mesh belt mesh part or the guide member on the side of the belt and remains in the furnace. However, the change of the lot of the processed product is likely to cause mixing of different materials into which the above-mentioned residual product mixes in the subsequent lot.In addition, the processed product is dropped into the quenching tank and the quenched product is placed on the mesh belt of the tempering furnace. Along with the drop supply, there is a problem that a dent is generated on the surface of the processed product due to the collision between the processed products. Furthermore, when changing the lot of processed products, even if the heating temperature and atmosphere in the furnace are the same, the lot interval on the belt must be increased in order to avoid confusion between different materials, and in the tempering furnace, In many cases, it is necessary to change the set temperature and furnace atmosphere. However, since these changes take time, especially in the case of small lots, there is a problem that the operation rate of the entire apparatus is low and productivity is inferior. It was.

  The present invention is intended to solve the above-mentioned conventional problems, and it can prevent the mixing of different materials and the occurrence of dents in the processed product, and the operation interruption time associated with the lot switching of the processed product can be shortened, resulting in a high operating rate. It aims at providing the continuous heat processing apparatus obtained.

  In order to achieve the above object, a continuous heat treatment apparatus according to claim 1 is a roller hearth type quenching furnace and a roller hearth that conveys a heated object in which a processed product is accommodated in a basket placed on a tray. One of the two tempering furnaces is used as the object to be heated sent from the quenching tank provided on the outlet side of the quenching furnace. The present invention is characterized in that a transport device for transporting is provided at the inlet portion.

  According to the means of claim 1, the processed product is conveyed in the quenching furnace and immersed in the quenching tank in the state of being accommodated in the basket, and then subjected to quenching treatment. Accordingly, the temperature is transferred to one predetermined tempering furnace in which the furnace temperature and the atmosphere in the furnace are adjusted, and the inside of the tempering furnace is transported and tempered. If it is necessary to change the furnace temperature or atmosphere in the tempering furnace when changing the lot of the processed product, during the tempering of the processed product of the preceding lot in one tempering furnace, the furnace temperature in the other tempering furnace Prepare the tempering by adjusting the atmosphere in the furnace and tempering, and by switching the transfer destination after quenching the processed product of the subsequent lot to the other tempering furnace, Long-term operation interruptions are unnecessary, and the operating rate of the entire processing apparatus is improved. In addition, during the above quenching to tempering process, the processed product is accommodated in the basket. During this period, the processed product falls in a loose state and collides with each other, and in the quenching furnace and the tempering furnace or both. The treated product does not remain in the transfer path between the furnaces in a loose state, and it is possible to prevent dents in the treated product and mixing of different materials into subsequent lots due to the remaining product, and the heating temperature and atmosphere in the furnace are the same. When switching lots of processed products in this case, even if the lot interval (basket interval) is shortened, mixing of different materials does not occur.

In this invention, the two tempering furnaces may be tempering furnaces having the same structure, but at least one of the two tempering furnaces as in the invention of claim 2. Is a multipurpose tempering furnace capable of switching between oxidative tempering and non-oxidative tempering and / or blackening tempering, according to the specifications required for tempered products, Non-oxidizing tempering and / or blackening tempering can be freely selected and performed. In this invention, oxidation tempering means tempering in an oxidizing (atmosphere) atmosphere, non-oxidizing tempering means tempering in a non-oxidizing atmosphere, and blackening tempering is described in, for example, Japanese Patent No. 2611801. Thus, it shall refer to tempering (blackening treatment method) in which a black Fe ₃ O ₄ oxide film is formed on the surface of the workpiece simultaneously with tempering.

  In the present invention, the supply of the basket with the new processed product to the quenching furnace and the removal of the tempered processed basket from the tempering furnace are carried out by a separate device, and the used basket and tray are processed by a heat treatment apparatus. However, the basket portion of the heat-treated material after tempering is lifted to the outlet side of the two tempering furnaces as in the invention of claim 3. And a processed product dispensing device for returning the basket to the tray after dispensing the processed product in the basket, and returning the basket and tray emptied by the dispensing to the entrance of the quenching furnace. If the return path and the supply device for supplying new processed products are provided in the returned empty basket, the basket and tray are circulated through the return path. Since, basket and tray requires only a small number as compared with the case of timely re-use and stored out of the system of the above-described heat treatment apparatus.

  In the present invention, the empty basket after the processed product is discharged may be returned to the entrance of the quenching furnace through the return path as it is. However, as in the invention according to claim 4, the basket is placed in the return path. If a remaining product detection device for detecting a remaining product is provided, even if a processed product remains in the basket, it can be detected by the remaining product detection device.

  In the present invention, the tray after the processed product is discharged may be returned as it is to the entrance of the quenching furnace through the return path. However, as in the invention according to claim 5, the basket is held in the return path. If a tray reversing device is provided to turn the tray upside down in the top, the tray is always heated from only one side in the furnace and is prevented from being worn out by being cooled from only one side in the quenching tank. it can.

  According to the present invention, the processed product is quenched and tempered in a state of being accommodated in the basket, so that during this time, the processed product is dropped or collided due to collision, and the processed product remains to the subsequent lot. The mixing of different materials is prevented. In addition, since there are two tempering furnaces, when changing the tempering conditions such as furnace temperature and furnace atmosphere associated with the lot switching of processed products, new tempering conditions in the other tempering furnace during the tempering process of the preceding lot Because preparations for tempering can be made, the operation interruption time associated with lot switching can be shortened, and a high operating rate can be obtained, and the processed products are conveyed in the furnace while being accommodated in a basket, so that the same tempering can be performed. When changing the lot of processed products under the tempering or tempering conditions, even if the lot interval (basket interval) is small, mixing of different materials will not occur, and the operating rate will be greatly improved especially in the case of small lots. .

  In addition to the above effects, according to the invention described in claim 2, according to the specifications required for the tempered product, oxidation tempering, non-oxidation tempering and / or blackening tempering is freely performed after quenching. It can be selected and performed, and many types of tempered products can be obtained.

  In addition to the above effects, according to the invention described in claim 3, since the basket and the tray are circulated through the return path, the basket and the tray are stored outside the system of the heat treatment apparatus and reused as appropriate. A small number is required compared to the case, and space for storing extra baskets and trays is also unnecessary.

  In addition to the above effect, according to the invention described in claim 4, even if a processed product remains in the basket, it can be detected by the remaining product detection device, and mixed with different materials when changing the lot. Can be reliably prevented.

  In addition to the above effects, according to the invention described in claim 5, the tray can be prevented from being heated (cooled) from only one side of the fixed surface in a furnace and worn out, and the life of the tray can be extended. be able to.

  Hereinafter, an embodiment of the present invention will be described with reference to an example shown in FIGS. FIG. 1 shows the entire continuous heat treatment apparatus 1, 2 is a quenching furnace, 3 is a tempering furnace, 4 is a multi-purpose tempering furnace, and each of these furnaces is treated in a basket 6 placed on a tray 5. Is constituted by a roller hearth type furnace in which a heated object W is conveyed in the furnace by a hearth roll. In this example, the processed product 7 is a small part made of a magnetic material (steel material), and the magnetic residue detection device 18 (described later) is used for detecting the remaining product. The tray 5 is made of austenitic heat resistant steel (non-magnetic material). 8 denotes a workpiece W sent from a quenching tank 21 provided on the outlet 2b side of the quenching furnace 2 via a roller conveyor 22; an inlet 3a part of the tempering furnace 3 or an inlet 4a part of the multipurpose tempering furnace 4; A self-propelled traversing carriage 9 having a roller conveyor at the top is movably mounted on a rail 10.

  Similarly, in FIG. 1, reference numeral 11 denotes a basket of the object to be heated W sent from the outlet 3 b of the tempering furnace 3 and the outlet 4 b of the multipurpose tempering furnace 4 through the cooling device 40 and the roller conveyor 41 common to both furnaces. The processed product dispensing device 12 for dispensing the processed product 7 in the apparatus 6 includes an empty basket 6 and a tray 5 after the dispensing, and the inlet 2a portion of the quenching furnace 2 (in this example, the installation of the roller conveyor 23 reaching the inlet 2a). A return path returning to the input end portion 23a is configured such that the transverse carriages 13 and 14 having the same configuration as the transverse carriage 9 are movably mounted on rails 15 and 16. Reference numeral 17 denotes a tray for turning the tray 5 upside down. A reversing device, 18 is a remaining product detecting device for detecting the remaining product in the basket 6, 19 is a feed device for supplying a new processed product 7 into the returned empty basket 6, and these devices are used for the return path 12. On the side or middle of The structure etc. will be described later, and 31 designates that the tempered product is transferred from the feed end of the roller conveyor 32 provided on the outlet 3b side of the tempering furnace 3 to the outlet 4b part of the multipurpose tempering furnace 4. A traversing carriage 33 having the same configuration as the traversing carriage 9 is placed on a rail 34 so as to be able to run.

  Next, in FIG. 2, 24 is a pre-cleaning device provided in the intermediate part of the roller conveyor 23, and 25 is an intermediate cleaning device provided in the intermediate part of the roller conveyor 22, both of which immerse the object to be heated W in the hot water tank. The quenching tank 21 is also used for quenching by heating the heated article W in the cooling oil in the tank. The quenching furnace 2 performs quenching in the RX gas atmosphere supplied from the RX gas generator 26 and includes a radiant tube 27 as a heating device. Further, the material supply device 19 supplies a predetermined amount of the new processed product 7 stored in a hopper (not shown) into the empty basket 6 on the traversing carriage 14 by the electromagnetic feeder 20.

  Next, as shown in FIG. 3, the tempering furnace 3 performs tempering in an oxidizing (atmospheric) atmosphere, and includes a direct-burn burner 35 as a heating device.

Next, as shown in FIG. 4, the multipurpose tempering furnace 4 includes a non-oxidizing tempering that performs tempering using a radiant tube 43 as a heating source in an N ₂ gas atmosphere supplied from the N ₂ gas generator 42, and oxidation ( Switching between oxidation and tempering, in which tempering is performed using an open flame burner 44 as a heating source in the atmosphere) according to the tempering specification of the processed product 7. Reference numeral 45 denotes a rust preventive oil tank in which a non-oxidized tempered product is immersed, and N ₂ gas is also supplied to the front chamber 46, the rust preventive oil tank chamber 47, and the rear chamber 48 at the time of non-oxidized temper. The cooling device 40 cools the object to be heated W on the roller conveyor 49 by blowing air Q for cooling.

  Further, as shown in detail in FIG. 5, the processed product dispensing apparatus 11 is driven to open and close by an air cylinder 54 on the lower surface side of a lifting platform 53 that can be moved up and down along a guide 52 attached to a platform 51 fixed on a foundation. The lifting device 58 is provided so as to drive the lifting platform 53 up and down by the motor 57 via the chain 56, and the rail 61 fixed on the upper beam portion of the platform 51 is moved back and forth by the motor 61. A holding base 64 is pivotally supported around a horizontal axis by a support shaft 65 at a lower end portion of a frame body 63 that opens in a downward U-shape to avoid interference with the lift base 53 on the driven carriage 62. Then, a motor 66 for rotationally driving the holding table 64 is provided. The holding table 64 has a guide piece 67 with which the outer surface portion of the basket 6 is fitted, and an air cylinder drive type clamping device (illustrated) similar to the clamping device 55. No) and an inverting device 68 comprising providing the, and an electromagnetic feeder 69 supported on frame 51.

  The payout operation by the processed product payout device 11 is as follows. That is, the lifting device 58 is lowered as shown by the chain line on the tempered workpiece W transferred from the delivery end of the roller conveyor 41 onto the traversing carriage 14, and the basket 6 is moved by the clamp 55. Is lifted to the position indicated by the solid line. Next, the reversing device 68 is traversed so that the holding base 64 is positioned directly below the lifting base 53 as shown in the chain line, and then the lifting base 53 is driven downward to move the basket 6 onto the holding base 64. And the basket 6 is clamped to the holding table 64 by the clamping tool of the holding table 64 and traversed to the position shown by the solid line. The processed product 7 is dispensed onto the electromagnetic feeder 69, and the processed product is supplied to a collecting device unit (not shown) by the electromagnetic feeder 69 and stored in a component storage can. The inverted basket 6 is returned to the original direction together with the holding table 64 by the motor 61, and is gripped by the lifting platform 53 by each operation opposite to the above, and is moved on the traversing carriage 13 (in this example, it is reversed by the tray reversing device 17 described later). It is returned to the tray 5 (after).

  Further, as shown in FIGS. 5 to 8, the tray reversing device 17 fixes the gantry 73 on the foundation at the positions corresponding to the interval portions of the short roller conveyors 71 and 72 arranged with the interval M. A single support shaft 76 is supported by rotating around a horizontal axis via a bearing 75 at the tip of each piston rod of a pair of air cylinders 74, 74 fixed to the upper beam 73 a of the gantry. Clamping tools 78, 78 having a U-shaped cross section are fixedly attached to the tip ends of piston rods of a pair of gripping air cylinders 77, 77 that are fixedly mounted, and a motor with a brake for rotating the support shaft 76 is mounted. The attachment block 80 attached to the leg portion 79 is fitted to the inner side surface of one side column 73b formed by facing the grooved steel material of the gantry 73 so as to be movable up and down to prevent free rotation of the support shaft 76. Non-rotating function Formed composed.

  The tray reversing operation by the tray reversing device 17 is as follows. That is, first, as shown by a chain line in FIG. 6, the air cylinders 74, 74 are driven to project and the clamps 78, 78 together with the support shaft 76 are lowered to the position shown in the chain line. The empty tray 5 being lifted is transferred onto the roller conveyors 71 and 72 so that the intermediate portion of the tray is positioned at the interval M as shown by the solid line, and then clamped by the gripping air cylinders 77 and 77. 78 and 78 are driven forward, the tray 5 is gripped from both sides, and then the clamp tool 78 is lifted to the position shown by the solid line (however, the clamp tool 78 is in the advanced state) together with the support shaft 76. After the rotational drive, the tray 5 after 180 degrees reversed held on the lower side of the support shaft 76 is placed on the roller conveyors 71 and 72, and then the clamps 78 and 78 are retracted. Then, the support shaft 76 and the clamp tool 78 are moved up again, the support shaft is rotated 180 degrees to return to the state shown in the solid line, and the tray 5 after the inversion is moved from the roller conveyors 71 and 72 onto the traversing carriage 13. Returned and ready for placement of empty basket 6 after processed goods are dispensed.

  Further, as shown in FIGS. 9 and 10, the remaining product detection device 18 provided in the return path 12 is provided with non-rotating rollers 82 and 83 that are rotatably supported by a gantry 81 and a driving roller 84 that is rotationally driven by a motor 85. A belt 86 made of a magnetic material (rubber in this example) is wound around to form a belt conveyor 87. A permanent magnet 88 is installed below the upper running surface of the belt 86 and the upper beam 89 below the frame 81 A detection coil 90 that detects a change in magnetic flux is provided opposite to the permanent magnet 88, and the output end of the detection coil 90 is connected to a detection circuit 91 including an amplifier, a comparator, a switching circuit, and the like. An alarm device 92 is connected to the output side of the detection circuit.

  In the remaining product detection device 18, a tray 5 (both made of austenitic heat-resistant steel, which is a nonmagnetic material) on which an empty basket 6 conveyed from the processed product delivery device 11 by the traversing carriage 13 is placed at a constant speed. It is transferred onto the other traversing carriage 14 via the belt conveyor 87 operated in the above. At this time, if there is a remaining product P of the processed product 7 in the basket 6, the magnetic flux in the 90 parts of the detection coil is generated by the eddy current generated in the remaining product P made of a magnetic material (steel material) that passes through the static magnetic field of the permanent magnet 88. When the electromotive force value of the detection coil 90 that detects this magnetic flux change exceeds a predetermined value, the detection circuit 91 issues an output signal to the alarm device 92, and the alarm device 92 generates a remaining product P due to the sounding. Be reported.

  In order to perform the heat treatment of the treated product 7 by the continuous heat treatment apparatus 1 having the above configuration, first, according to the specifications required for the tempered product, whether the tempering is performed in the tempering furnace 3 or the multipurpose tempering furnace 4, In the multipurpose tempering furnace 4, it is selected whether to perform oxidation tempering or non-oxidizing tempering. And the to-be-heated material W which put the basket 6 supplied with the processed goods 7 by the material supply apparatus 19 on the tray 5 is sequentially inserted in the quenching furnace 2 at predetermined small intervals, and it quenches. The object to be heated W is first cleaned by the pre-cleaning device 24, and then tact-conveyed in the quenching furnace 2 by a hearth roll, heated to a predetermined temperature by the radiant tube 27 in the RX gas atmosphere, and immersed in the quenching tank 21. Then, after rapid cooling and cleaning by the intermediate cleaning device 25, the transfer device 8 is charged into the furnace from the entrance of the selected tempering furnace 3 or multipurpose tempering furnace 4 and tempered.

  In the case of tempering by the tempering furnace 3, the heated object W is heated to a predetermined temperature by an open flame burner 35 in an oxidizing atmosphere, conveyed to a cooling device 40 by a traverse carriage 33 via a roller conveyor 32, and cooled. Thus, tempering of the processed product 7 is completed.

In the case of oxidation tempering by the multipurpose tempering furnace 4, the workpiece W is heated to a predetermined temperature by an open flame burner 44 in an oxidizing atmosphere, and in the case of non-oxidizing tempering, by a radiant tube 43 in an N ₂ gas atmosphere. After being heated to a predetermined temperature and subjected to a rust prevention treatment by the rust prevention oil tank 45, it is conveyed to the cooling device 40 part through the traverse carriage 33 and cooled to complete the tempering of the processed product 7.

  The to-be-heated object W that has been tempered is sequentially transferred onto the traverse carriage 13 through the roller conveyor 41 as shown by a chain line in FIG. Before arrival, as described above, the processed product delivery device 11 delivers the processed product 7 in the basket 6 and the tray reversing device 17 reverses the tray 5 while the basket 6 is being held. The empty basket 6 is placed on the tray 5 that is turned upside down, is transported by the traversing cart 13 and passes through the remaining product detection device 18, and is then returned to the rear end of the return path 12 by the traversing cart 14. Here, a new processed product 7 is fed into the empty basket 6 by the feeding device 19 and used for quenching by the quenching furnace 2, and the basket 6 and the tray 5 are circulated and used in this way. The above process is repeated to perform continuous heat treatment of the processed product.

  When there is a remaining product P in the basket 6 when passing through the remaining product detection device 18, the remaining product detection is notified by the alarm device 92 as described above. By manually removing P, it is possible to reliably prevent the remaining product P from being mixed into the newly processed product 7 and from mixing different materials at the time of lot switching.

  When changing the tempering conditions such as furnace temperature (heating temperature) or furnace atmosphere when changing the lot of the processed product 7, the transfer destination of the quench processed product by the transfer device 8 is set to a new tempering condition. The tempering is performed by switching to a tempering furnace (tempering furnace 3 or multipurpose tempering furnace 4) different from that for the preceding lot. At this time, during the tempering process of the preceding lot, by adjusting the furnace temperature and atmosphere in the other tempering furnace and preparing for tempering, the operation interruption time associated with lot switching can be shortened. .

  The present invention is not limited to the above example. For example, the in-furnace structure of each of the quenching furnace 2, the tempering furnace 3, and the multipurpose tempering furnace 4, the atmosphere gas used, and before and after being placed before and after the furnace The processing apparatus or the like may be other than those described above, and performs blackening and tempering as described in, for example, Japanese Patent No. 2611801 in addition to or in place of the above-described oxidation and non-oxidation tempering. A tempering furnace or a multipurpose tempering furnace may be used.

  In the above example, the basket 6 is lifted by the lifting device 58 that constitutes a part of the processed product dispensing device 11 when the tray is reversed. Therefore, the configuration of the tray reversing device 17 is simplified and lifted. By sharing the apparatus 58, there is an advantage that the overall equipment cost is low and the installation space is small. In addition to this, the tray reversing apparatus is separate from the processed product dispensing apparatus 11, for example, return It is good also as a thing provided in the intermediate part of the path | route 12, etc., and the structure provided with the tray lifting apparatus only for an inversion apparatus.

  Further, as the remaining product detection device 18, other types of magnetic detection devices such as those using an electromagnet for generating magnetic flux, for example, the basket 6 portion is imaged from above by a CCD camera, and the light / dark density signal of this imaging screen is displayed. An image processing type residual product detection device that determines the presence or absence of a residual product P based on the image processing circuit may be used. In this case, the processed product 7 made of nonmagnetic material, the basket 6 made of magnetic material, the tray It can be suitably used for 5 grades.

It is a top view of the continuous heat processing apparatus which shows an example of embodiment of this invention. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG. It is CC sectional view taken on the line of FIG. It is the D section expanded sectional view of FIG. It is an arrow EE front view of the tray inversion apparatus in FIG. It is the FF sectional view taken on the line of FIG. It is the GG line expanded sectional view of FIG. It is the HH sectional view taken on the line of FIG. It is the II sectional view taken on the line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Continuous heat processing apparatus, 2 ... Quenching furnace, 2b ... Outlet, 3 ... Tempering furnace, 3a ... Inlet, 4 ... Multipurpose tempering furnace, 4a ... Inlet, 5 ... Tray, 6 ... Basket, 7 ... Processed goods, DESCRIPTION OF SYMBOLS 8 ... Conveyance apparatus, 11 ... Processed goods delivery apparatus, 12 ... Return path, 17 ... Tray reversing apparatus, 18 ... Remaining article detection apparatus, 19 ... Feeding device, 21 ... Quenching tank, 27 ... Radiant tube, 35 ... Direct flame burners, 42 ... _{N 2} gas generating apparatus, 43 ... radiant tube, 44 ... direct flame burners, 58 ... lifting apparatus, 68 ... inverter, 69 ... electromagnetic feeders, 74 ... air cylinder, 76 ... support shaft, 78 ... Clamping tool, 79 ... motor, 87 ... belt conveyor, 88 ... permanent magnet, 90 ... detection coil, W ... heated object, P ... remaining item.

Claims (5)

  A roller hearth-type quenching furnace for transporting a heated object containing a processed product in a basket placed on a tray in the furnace and two roller-hearth type tempering furnaces, and an outlet of the quenching furnace A continuous heat treatment characterized by comprising a transfer device for transferring the object to be heated sent from a quenching tank provided on the side to a predetermined inlet of one of the two tempering furnaces apparatus.   The continuous heat treatment apparatus according to claim 1, wherein at least one of the two tempering furnaces is a multipurpose tempering furnace capable of switching between oxidation tempering, non-oxidation tempering and / or blackening tempering. .   A processed product dispensing device that lifts the basket portion of the heated object after tempering upside down on the outlet side of the two tempering furnaces, disposes the processed product in the basket, and returns the basket onto the tray. And a return path for returning the basket and tray emptied by the payout to the entrance of the quenching furnace, and a feed device for supplying a new processed product into the returned empty basket. The continuous heat treatment apparatus according to claim 1, wherein the apparatus is a continuous heat treatment apparatus.   4. The continuous heat treatment apparatus according to claim 3, wherein a remaining product detection device for detecting a remaining product in the basket is provided in the return path.   5. The continuous heat treatment apparatus according to claim 3, wherein the return path is provided with a tray inversion device that inverts the tray while the basket is being lifted.

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