JP2010210194A - Heat treatment furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate uniform heating of a work piece 100, and to reduce abrasion of the inside thereof. <P>SOLUTION: This heat treatment furnace includes a furnace body 10 having a discharge port with a door 28, an air distribution device 12, a heating device 14 and a base 20. The heat treatment furnace further has an accelerating section 16, a partitioning wall 18, an induction section 22 and a decelerating section 24. The accelerating section 16 is disposed between the heating device 14 and the base 20. The accelerating section 16 accelerates the wind heated by the heating device 14. The induction section 22 is disposed under the base 20. The induction section 22 induces the wind colliding with the work piece 100. The decelerating section 24 id disposed under the base 20. The decelerating section 24 decelerates the wind colliding with the work piece 100. The accelerating section 16 accelerates the wind to apply the wind to the work piece 100. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a heat treatment furnace, and more particularly, to a heat treatment furnace that can reduce the deviation in temperature distribution when a workpiece is heated and can reduce wear inside itself.

  Patent Document 1 discloses a continuous heat treatment furnace. This continuous heat treatment furnace has an axial fan provided at the top of the furnace body, a heating device provided below it, a slit plate provided below it, and a beam provided below it (a workpiece is suspended on the beam). Can be lowered). According to the continuous heat treatment furnace described in Patent Document 1, it is possible to save human power as much as possible, improve productivity, uniform work quality, and improve thermal efficiency.

  Patent document 2 discloses a high-speed heating furnace. This fast heating furnace is surrounded by a refractory wall. This fire wall has a work carry-in entrance on a side surface. A furnace chamber (a furnace is provided with a burner) is provided at the lower part of the fast heating furnace. The fast heating furnace includes a cylindrical workpiece storage chamber concentrically arranged in the furnace chamber, and a circulation fan provided on the upper opening side of the workpiece storage chamber. A placement shelf for placing workpieces is provided in the workpiece storage chamber. A workpiece transfer path communicating with the workpiece transfer port of the furnace chamber is provided in parallel with the mounting shelf. A door for closing the work transfer port is provided on the outer wall surface of the work transfer port so as to be openable and closable. By operating the circulation fan, the hot air in the work storage chamber heated by the burner is sucked up from the upper opening and descends as a vortex in the circulation passage between the furnace chamber and the work storage chamber. At the same time, it is led from the lower opening of the workpiece storage chamber to the workpiece storage chamber. According to the fast heating furnace described in Patent Document 2, the internal stress accumulated in the workpiece during molding is effectively removed by rapidly heating and annealing the workpiece, and dimensional stability. Can be improved.

Japanese Patent Laid-Open No. 51-131408 JP 2003-183725 A

  However, the continuous heat treatment furnace disclosed in Patent Document 1 has a problem that the temperature near the center of the lower part of the workpiece tends to be low.

  If the fast heating furnace disclosed in Patent Document 2 is used, the temperature near the center of the lower part of the workpiece is less likely to be lowered. However, the fast heating furnace disclosed in Patent Document 2 has a problem that the inside of the furnace is easily worn.

  The present invention has been made to solve such problems, and the object of the present invention is to reduce the temperature distribution unevenness when the workpiece is heated, and to reduce the wear inside itself. An object of the present invention is to provide a heat treatment furnace.

  The heat treatment furnace of the present invention will be described with reference to the drawings. Note that the use of the reference numerals in the figure in this column is intended to assist understanding of the contents of the invention, and is not intended to limit the contents to the illustrated range.

  In order to solve the above problems, according to an aspect of the present invention, the heat treatment furnace includes a furnace body 10 having an opening with a door 28, a blower device 12, a heating device 14, and a table 20. The air blower 12 is accommodated in the furnace body. The heating device 14 is accommodated in the furnace body 10. The heating device 14 heats the wind generated by the operation of the blower device 12. The stand 20 is accommodated in the furnace body 10. The workpiece 100 is placed on the table 20 such that the wind heated by the heating device 14 collides with the workpiece 100. In this case, the heating device 14 is disposed below the blower device 12. A table 20 is disposed under the heating device 14. The heat treatment furnace further includes an acceleration unit 16, a partition wall 18, an induction unit 22, and a deceleration unit 24. The acceleration unit 16 is disposed between the heating device 14 and the table 20. The acceleration unit 16 accelerates the wind heated by the heating device 14. The partition wall 18 is housed in the furnace body 10 and surrounds the workpiece 100 placed on the table 20. The guiding portion 22 is disposed under the table 20. The guide unit 22 guides the wind that has collided with the workpiece 100 from the bottom of the table 20 to the blower 12. The deceleration unit 24 is disposed below the table 20. The deceleration unit 24 decelerates the wind that has collided with the workpiece 100. The acceleration unit 16 accelerates the wind so that the wind hits the workpiece 100.

  The acceleration unit 16 accelerates the wind heated by the heating device 14 so that the wind hits the workpiece 100. When the accelerated wind hits, the temperature rise rate of the workpiece 100 increases. By being faster, the wind flows faster along the workpiece 100 than if it was not fast. Since the wind flows fast along the workpiece 100, the possibility of the wind moving away from the workpiece 100 and drifting inside the partition wall 18 is reduced, and the thermal efficiency for heating the workpiece 100 is improved. Thereby, a lot of heat can be given to many parts of the workpiece 100 from the wind. Accordingly, the workpiece 100 can be easily heated evenly. Furthermore, since the speed reduction part 24 arranged under the table 20 decelerates the wind that collides with the workpiece 100, even if a substance that promotes wear inside the heat treatment furnace is included in the wind, It becomes easy to leave. As a result, the heat treatment furnace according to an aspect of the present invention can reduce its own internal wear.

  Moreover, it is desirable that the heating device 14 described above includes a heating chamber 42 having an inlet 50 and an outlet 52 and a heat source 40. Wind flows from the inflow port 50. The heated wind is discharged from the discharge port 52. The heat source 40 is disposed in the heating chamber 42. In this case, the acceleration unit 16 includes a plurality of tubes 62. In this case, the sum of the cross-sectional areas of the plurality of tubes 62 is smaller than the opening area of the discharge port 52. In this case, the plurality of tubes 62 are arranged so as to communicate the space surrounded by the partition wall 18 with the heating chamber 42.

  The sum of the cross-sectional areas of the plurality of tubes 62 is smaller than the opening area of the discharge port of the heating chamber 42. Thereby, the wind is accelerated. Furthermore, the structural material can be made smaller compared to the case where wind is generated only by the ability of the blower 12 itself.

  In addition, it is desirable that the central axes of the plurality of tubes 62 described above are parallel to each other.

  Since the central axes of the plurality of tubes 62 are parallel to each other, the wind tends to be laminar. When the wind becomes laminar, it is avoided that the wind collides and the flow velocity decreases accordingly. When this is avoided, the workpiece can be efficiently heated as compared with a heat treatment furnace having a blower having the same ability.

  Further, it is desirable that the length of the tube 62 described above is longer than the diameter of the tube 62.

  Since the length of the tube 62 is longer than the diameter of the tube 62, the wind tends to be laminar. When the wind becomes laminar, it is avoided that the wind collides and the flow velocity decreases accordingly. When this is avoided, the workpiece can be efficiently heated as compared with a heat treatment furnace having a blower having the same ability.

  Moreover, it is desirable that the speed reduction part 24 described above is provided between the bottom of the base 20 and the blower 12 and is a member that blocks the flow of wind.

  As described above, according to the heat treatment furnace according to the present invention, it is possible to reduce the deviation of the temperature distribution when the workpiece is heated, and to reduce the wear inside itself.

It is sectional drawing when the heat treatment furnace concerning embodiment of this invention is seen from the front. It is sectional drawing when the heat processing furnace concerning embodiment of this invention is seen from the side. It is a perspective view, such as a blowing nozzle plate, according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  The configuration of the heat treatment furnace according to the present embodiment will be described with reference to FIGS. 1 and 2. The heat treatment furnace according to the present embodiment includes a blowing device 12, a heating device 14, a blowing nozzle plate 16, a partition wall 18, a rooster 20, a hearth portion 22, a sand removal plate 24, a solenoid valve 26, And a door 28.

  The blower 12 is disposed on the top of the furnace body 10. The blower 12 generates wind by operating. In this embodiment, the air blower 12 is a plate fan. The capacity of the blower 12, that is, the amount of wind generated by the blower 12 is determined by the size of the workpiece 100.

  The heating device 14 is disposed below the blower device 12. The heating device 14 heats the wind generated by the operation of the blower device 12. The detailed configuration of the heating device 14 will be described later.

  The blowout nozzle plate 16 is disposed under the heating chamber 42. The blowing nozzle plate 16 accelerates the gas discharged from the heating device 14 to a flow rate of 25 m / second or more. The detailed configuration of the blowout nozzle plate 16 will be described later.

  The partition wall 18 surrounds the workpiece 100. The rooster 20 is a platform for placing the workpiece 100 such that the wind heated by the heating device 14 collides with the workpiece 100. The hearth 22 guides the wind that has collided with the workpiece 100 from below the rooster 20 to the blower 12. In the present embodiment, the hearth part 22 is integrated with the furnace body 10. The sand removal plate 24 decelerates the wind that has reached the hearth 22 after colliding with the workpiece 100. That is, the sand removal plate 24 according to the present embodiment is a member that is provided between the bottom of the rooster 20 and the blower 12 and prevents the above-described wind flow. Thereby, since the sand contained in the wind falls to the bottom of the hearth part 22, those sands are removed. The electromagnetic valve 26 is disposed on the inner wall of the furnace body 10 and on the upstream side of the blower 12. Air outside the furnace body 10 is sucked into the furnace body 10 through the electromagnetic valve 26. In the present embodiment, the amount of air sucked is a small amount that does not affect the temperature in the furnace. The oxygen concentration inside the furnace body 10, which has been reduced by the heat generated by the burner 40 with a combustion cylinder, which will be described later, rises to about 10% by the intake of air outside the furnace body 10. The door 28 closes the opening of the furnace body 10. The workpiece 100 is inserted from this opening into a space surrounded by the partition wall 18 (hereinafter, a space surrounded by the partition wall 18 is referred to as a “processing chamber” in this embodiment), and is placed on the rooster 20. Heated. The heated workpiece 100 is removed from the processing chamber.

  The configuration of the heating device 14 according to the present embodiment will be described with reference to FIG. The heating device 14 according to this embodiment includes a burner 40 with a combustion cylinder and a heating chamber 42. The tip of the combustion cylinder of the burner 40 with the combustion cylinder is disposed at the center of the heating chamber 42. The burner 40 with a combustion cylinder is a heat source that generates heat. The heating chamber 42 mixes the gas sent as wind from the blower 12 with the high-temperature gas emitted from the burner 40 with the combustion cylinder. The heating chamber 42 has an inlet 50 and an outlet 52. The wind sent from the blower 12 flows in from the inflow port 50. The air heated by the burner 40 with the combustion cylinder is discharged from the discharge port 52. As is apparent from FIG. 3, two air blowers 12 are provided in this embodiment. Since two air blowers 12 are provided, there are two inflow ports 50. In the present embodiment, there is one discharge port 52. The heating device 14 may have an electric heater as a heat source instead of the burner 40 with the combustion cylinder. When the heating device 14 includes the burner 40 with the combustion cylinder, the burner 40 with the combustion cylinder is desirably a burner that can stably burn even with excess air having an air ratio of 1.3 or more.

  With reference to FIG. 3, the structure of the blowing nozzle plate 16 according to the present embodiment will be described. The blowout nozzle plate 16 according to the present embodiment includes a first plate 60, a number of nozzle tubes 62, and a second plate 64. The first plate 60 is a member for connecting the nozzle tube 62 to the heating chamber 42. The first plate 60 has a number of holes. The inside of each nozzle tube 62 communicates with the heating chamber 42 through this hole. At both ends of the nozzle tube 62, a cone-like structure with the tip removed is attached. The inner diameter of the nozzle tube 62 is smaller than the total length of the nozzle tube 62. The central axes of the nozzle tubes 62 are parallel to each other and face the up-down direction. Since the central axis of the nozzle tube 62 is directed in the vertical direction, the opening of the nozzle tube 62 is directed toward the workpiece 100. Since the opening of the nozzle tube 62 faces the workpiece 100, the workpiece 100 is exposed to gas wind. However, in the present embodiment, the nozzle tubes 62 are parallel to each other even if they are not parallel in a strict sense as long as they are parallel with an accuracy that can be realized when the nozzle tube 62 is connected to the heating chamber 42. It is considered. The nozzle tube 62 is fixed to the first plate 60 and the second plate 64 by welding. The inside of the nozzle tube 62 communicates with the heating chamber 42 through each hole of the first plate 60. The second plate 64 is connected to the partition wall 18. The second plate 64 also has a number of holes. The inside of the nozzle tube 62 communicates with the processing chamber through each hole of the second plate 64. Note that the sum of the cross-sectional areas of all the nozzle tubes 62 attached to the first plate 60 is smaller than the opening area of the discharge port of the heating chamber 42 facing the first plate 60.

  Next, the movement of the gas in the heat treatment furnace according to the present embodiment, the transition of the temperature rise of the workpiece 100, and the removal of sand will be described.

  The air blower 12 generates a gas wind by operating. The wind is heated by the heating device 14. The heated wind flows from the heating chamber 42 into the blowing nozzle plate 16. As described above, the sum of the cross-sectional areas of all the nozzle tubes 62 attached to the first plate 60 is smaller than the area of the discharge port of the heating chamber 42 facing the first plate 60. Thereby, the flow velocity of the gas flowing from the heating chamber 42 into the blowing nozzle plate 16 is increased. As a result, the gas is accelerated. Further, the nozzle tube 62 is a tube having an inner diameter smaller than the entire length. Since the inner diameter of the nozzle tube 62 is smaller than the total length, the gas flow flowing from the nozzle tube 62 into the processing chamber is a laminar flow. Since the gas flow is a laminar flow, the gas goes straight down directly in the processing chamber. Since the gases are directed straight down, there is not much reduction in their flow rates due to collisions between the gases. Those gases collide with the workpiece 100. When colliding with the workpiece 100, the speed of the gas remains high. In general, as the gas speed increases, the amount of heat transfer to the workpiece 100 increases. For this reason, also in this embodiment, when high-speed gas is made to collide with the workpiece 100, compared with the case where low-speed gas is made to collide with the workpiece 100, the thermal efficiency for heating the workpiece 100 is improved. Furthermore, depending on the speed of the gas, the air layer on the surface of the workpiece 100 is destroyed by the impact of gas collision. In this case, since the air layer on the surface of the workpiece 100 is destroyed, the temperature increase rate of the workpiece 100 is increased.

  Further, in the present embodiment, most of the gas that has collided with the workpiece 100 and the gas that has passed by the workpiece 100 goes to the hearth 22. This is because the flow velocity is originally high. Since most of these gases go to the hearth 22, the entire workpiece 100 is in full contact with the hot gas. As a result, the temperature distribution in the workpiece 100 approaches evenly.

  Further, the gas ejected from the blowout nozzle plate 16 also applies an impact to the sand adhering to the surface of the workpiece 100 (which was a part of the sand mold at the time of casting) and transfers heat. The impact of the sand causes the sand to fall off from the surface of the workpiece 100 quickly. In addition, as described above, when the air outside the furnace body 10 enters the furnace body 10, the oxygen concentration of the gas circulating inside the furnace body 10 is about 10%. Since the sand is heated by the gas and the oxygen concentration of the gas is about 10%, the alteration of the resin binding the sands is promoted. Since the alteration of the resin is promoted, the loss of sand is also promoted. The dropped sand drifts in the gas that has collided with the workpiece 100 or in the gas that has passed next to the workpiece 100. As a result, the dropped sand is also directed to the hearth 22.

  The gas and sand are reversed at the hearth 22, pass through between the partition wall 18 and the furnace body 10, and rise inside the furnace body 10. A sand removal plate 24 is attached to the hearth 22. The sand removing plate 24 removes a part of the sand floating in the gas. At this time, the gas is decelerated. The decelerated gas passes through between the partition wall 18 and the furnace body 10 and further decelerates while rising in the furnace body 10. The flow velocity at this point in the present embodiment is 5 m / sec or less. As the gas decelerates, the sand floating inside the gas returns to the hearth 22. The sand removed from the gas is discharged out of the furnace through an accumulation hopper provided at the bottom of the hearth part 22. By removing the sand, wear of the equipment in the furnace due to the sand entering the blower 12 is suppressed.

  As described above, according to the heat treatment furnace according to the present embodiment, the deviation of the temperature distribution when the workpiece 100 is heated can be reduced, the internal stress of the workpiece 100 can be well removed, and It is possible to reduce the internal wear of the. Hereinafter, these things are demonstrated concretely.

  An old heat treatment furnace as disclosed in Patent Document 1 uses a heat transfer by convection to heat a workpiece. Since heat transfer by convection is used, the combustion chamber that generates high-speed and high-temperature gas and the heating chamber that heats the workpiece must be at the same temperature. For this reason, in order to quickly heat a workpiece by such a heat treatment furnace, a large capacity axial fan is required. Furthermore, such heat treatment furnaces require trays, baskets and the like for transporting workpieces in the furnace. This means that heat is expended to raise the temperature of the tray or basket. The fact that heat is consumed for the temperature rise of trays and baskets increases the need for large capacity axial fans.

  However, it is difficult to incorporate a large capacity axial fan into the heat treatment furnace. Because it is difficult, it is also difficult to heat the workpiece quickly. Moreover, it is difficult for high-temperature gas flowing at high speed to collide with the workpiece. The maximum gas velocity of heat treatment furnaces that have been around for a long time is about 2 m / min.

  Furthermore, in the case of an old type heat treatment furnace whose axial flow fan sends the gas downward, the gas that hits the workpiece and the gas that passes through the workpiece is the suction section of those gases (they At the entrance of the passage for returning the gas to the axial fan. Since gas collects in the suction part, the temperature of the part of the workpiece away from the suction part is not so high.

  In order to make the temperature distribution in the workpiece close to uniform, the direction in which the axial fan sends out gas may be upward as disclosed in Patent Document 2. In this way, the gas descends from the ceiling of the furnace along the inner wall to the bottom of the furnace.

  In this case, there is a problem that when the workpiece to which the sand is attached is heated, the blades of the axial fan are easily worn. This problem is caused by the close distance between the axial fan and the workpiece. This is because the gas velocity is partially increased between the axial fan and the workpiece when the distance is close. As the gas speed increases, the axial fan sucks sand. This sand makes the blades of the axial fan severely worn. Because of this problem, large capacity axial fans cannot be installed. Incidentally, when the direction in which the axial flow fan sends out gas is upward, the average gas velocity in the whole furnace is lower than when the axial fan is directed downward. Because it is lower, sand floating in the gas is effectively removed.

  As is apparent from the above description, according to the conventional heat treatment furnace, it is difficult to quickly increase the temperature of the workpiece. Even if the temperature can be increased, the temperature distribution in the workpiece is likely to be biased, or the wear of the blades of the axial fan is likely to proceed.

  Furthermore, in the case of the fast heating furnace disclosed in Patent Document 2, the door is opened and closed when the workpiece is taken in and out during the heat treatment operation. Since the door is opened and closed, the furnace temperature decreases due to outflow of gas in the furnace and intrusion of outside air from the outside of the furnace. When the furnace temperature falls, the temperature rise of the workpiece in the heating zone in the furnace becomes worse. Furthermore, if the tempering temperature of the workpiece in the soaking zone is below a specified temperature, the performance of the workpiece is adversely affected.

  On the other hand, the heat treatment furnace according to the present embodiment has a blowout nozzle plate 16. The blowing nozzle plate 16 accelerates the wind heated by the heating device 14. Since the wind is accelerated, gas can collide with the workpiece 100 as a high-speed wind without increasing the capacity of the blower 12. Thereby, the temperature of a workpiece can be raised rapidly. Further, since the gas flows as a high-speed wind, the gas that collides with the workpiece 100 or the gas that has passed through the workpiece 100 reaches the hearth 22 as it is. Since the gas reaches the hearth part 22 as it is, it is suppressed that the gas collects in the portion corresponding to the suction part described above. Since this is suppressed, it is easy to make the temperature distribution inside the workpiece 100 close to uniform. Since it is easy, the internal stress of the workpiece 100 is well removed. Since the internal stress of the workpiece 100 is well removed, the quality of a product completed by further processing the workpiece 100 is high. In addition, since the wind accelerated by the blowout nozzle plate 16 serves as an air curtain, a large amount of external air hardly enters even when the door 28 is opened and closed.

  In the heat treatment furnace according to the present embodiment, the gas circulating at a high speed in the furnace contains high-concentration oxygen, and the gas collides with the sand attached to the workpiece 100 at a high speed. Efficient sand can be removed. Since sand is efficiently removed, the heat treatment time is shortened. When the heat treatment time is shortened, a large energy saving effect is obtained.

  As described above, the heat treatment furnace according to the present embodiment can cause the workpiece 100 to collide with the gas at a high speed even if the capacity of the blower 12 is not so high. Accordingly, the capacity of the blower 12 and the heating device 14 can be reduced as compared with the conventional heat treatment furnace having the same capacity. Since the capacity of the blower 12 and the heating device 14 is small, the heat treatment furnace according to this embodiment is smaller than the conventional heat treatment furnace having the same capacity. The smaller the space required for installation. Since the capacity of the blower 12 and the heating device 14 is small, the structural material of the furnace body 10 can be simplified as compared with the conventional heat treatment furnace having the same capacity. In addition to reducing the space required for installation, the structural material of the furnace body 10 can be simplified, so that the equipment cost is lower than that of a conventional heat treatment furnace having the same capacity.

  Furthermore, the heat treatment furnace according to the present embodiment includes a sand removal plate 24. Since the sand removal plate 24 is provided, the sand floating in the gas is efficiently removed. Since sand is removed, wear in the blower 12 is kept low. In addition, in the heat treatment furnace according to the present embodiment, the blower 12 is disposed at a position that is most downstream as viewed from a place where sand is mixed into the wind (the surface of the workpiece 100). During this time, sand mixed in the wind is removed sequentially. Since the sand is removed, the sand in the wind is considerably less when the wind reaches the blower 12. Since sand is reduced, wear of the blades of the blower 12 is suppressed.

  The embodiments disclosed herein are illustrative in all respects. The scope of the present invention is not limited based on the above-described embodiment, and various design changes may be made without departing from the spirit of the present invention.

  For example, the electromagnetic valve 26 may not be provided. Moreover, the number of the air blowers 12 and the number of the burners 40 with a combustion cylinder are not specifically limited. These numbers are desirably determined according to the size and number of workpieces 100 to be processed. Further, the nozzle tube 62 may not have a conical portion with the tip removed at both ends. The length of the nozzle tube 62 may be equal to or less than its diameter. The central axis of the nozzle tube 62 may be in different directions.

  Note that, as described above, the heat treatment furnace according to the present embodiment is smaller than a conventional heat treatment furnace having the same ability, and thus can be easily installed near the casting machine. If the heat treatment furnace according to the present embodiment is installed near the casting machine and the workpiece 100 is put into the furnace immediately after casting, the heat generated at the time of casting is cooled before the present embodiment is cooled. The heat treatment in the heat treatment furnace is started. In this case, the remaining heat is used effectively, so that energy saving can be achieved. In this case, a complicated structure in which a plurality of heat sources are provided in the furnace, divided into multiple bands, and each of them is controlled is not necessary. In this case, the temperature control can be simplified.

DESCRIPTION OF SYMBOLS 10 Furnace 12 Air blower 14 Heating device 16 Nozzle plate 18 Bulkhead 20 Rooster 22 Furnace floor part 22 Guide part 24 Sand removal plate 26 Solenoid valve 28 Door 40 Burner with a combustion cylinder 42 Heating chamber 50 Inlet 52 Outlet 60 Plate 62 Nozzle Tube 64 Plate 100 Workpiece

Claims (5)

A furnace body having an opening with a door;
A blower housed in the furnace body;
A heating device housed in the furnace and for heating the wind generated by the operation of the blower;
A heat treatment furnace comprising: a table for placing the workpiece so that wind heated by the heating device and impinged on the workpiece is contained in the furnace body;
The heating device is disposed under the blower;
The platform is disposed under the heating device;
An accelerating unit that is disposed between the heating device and the table and accelerates the wind heated by the heating device;
A partition wall enclosed in the furnace body and surrounding the workpiece placed on the table;
A guiding unit that is disposed under the table and guides the wind that has collided with the workpiece from the bottom of the table to the blower;
A decelerating portion disposed under the table and decelerating the wind that has collided with the workpiece;
The heat treatment furnace, wherein the acceleration unit accelerates the wind so that the wind hits the workpiece. The heating device is
A heating chamber having an inlet for the wind and an outlet through which the heated wind is discharged;
A heat source disposed in the heating chamber,
The acceleration unit has a plurality of tubes;
The sum of the cross-sectional areas of the plurality of tubes is configured to be smaller than the opening area of the discharge port,
2. The heat treatment furnace according to claim 1, wherein the plurality of tubes are arranged so as to communicate a space surrounded by the partition walls with the heating chamber.   The heat treatment furnace according to claim 2, wherein central axes of the plurality of tubes are parallel to each other.   The heat treatment furnace according to claim 2, wherein a length of the tube is longer than a diameter of the tube.   2. The heat treatment furnace according to claim 1, wherein the speed reduction portion is provided between the base and the blower, and is a member that blocks the flow of the wind.

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