JP2010059460A - Heat-treatment furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-treatment furnace with which the thermal-efficiency of a carburizing furnace at high temperature is improved and the whole equipment can be made to be saving-energy by utilizing the waste heat. <P>SOLUTION: The carburizing furnace 1 being this heat-treatment furnace, is provided with a carburizing-diffusion zone 11, in which to an objective material, the carburizing-treatment is applied with the first heating temperature (e.g. 950°C), and the second furnace, in which to the same objective material, a tempering-treatment is applied at the second heating temperature (e.g. 150°C) lower than the first heating temperature, and has a wall 15 between both furnaces for partitioning the first furnace and the second furnace, and an outer wall 16 for partitioning between the second furnace and the outer part, and the first furnace and the second furnace are disposed while adjoining through the wall 15 between both furnaces. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat treatment furnace for heat treating a stainless steel material or the like. More specifically, the present invention relates to a heat treatment furnace having a high temperature furnace that performs heat treatment at least at a high temperature and a low temperature furnace that performs heat treatment at a temperature lower than the processing temperature of the high temperature furnace.

  Conventionally, in a manufacturing process of gears and the like, for example, processing is performed in the order of a forging process → a heat treatment process → a machining process. As the heat treatment process, for example, carburizing treatment, tempering treatment, and the like are performed. Among these, the carburizing treatment is a heat treatment at a high temperature of about 950 ° C., for example. For this reason, for example, a carburizing furnace surrounded by a heat insulating wall made of 200 mm thick heat insulating brick and 50 mm thick rock wool is used. The tempering process is a heat treatment at a lower temperature than the carburizing process. Conventionally, a tempering furnace was provided independently of the carburizing furnace, and heat treatment was performed while controlling the temperature to an appropriate temperature.

As described above, as an energy saving measure in the process including the heat treatment at a high temperature and the heat treatment at a lower temperature than that, it has been proposed to distribute the exhaust gas of the high temperature furnace to the low temperature furnace. For example, Patent Document 1 discloses a heat treatment furnace in which a pair of coupled furnaces directly connected in an exhaust gas passage are stacked. According to the apparatus of this document, for example, a heating furnace for heating before quenching and a tempering furnace are connected by an exhaust gas passage, and high-temperature exhaust gas can be guided to the tempering furnace. In addition, it is said that the temperature can be individually adjusted by a damper provided in the exhaust gas passage.
Japanese Examined Patent Publication No. 4-63124

  However, although the exhaust gas is circulated in the heat treatment furnace described in Patent Document 1, the exhaust gas from the carburizing furnace cannot be circulated to the tempering chamber. This is because the atmospheric gas used in the carburizing process has an adverse effect on the tempering process. For this reason, this heat treatment furnace could not be applied for the purpose of effectively utilizing the heat of the carburizing furnace.

In addition, in an independent carburizing furnace as in the prior art, for example, the waste heat is as large as about 494 W / m ² , so that it cannot be said that the thermal efficiency is good. In order to improve thermal efficiency, it is possible to simply increase the thickness of the furnace wall. However, reducing the internal volume of the equipment can cause a decrease in productivity. Alternatively, increasing the wall thickness outward will increase the equipment size. Furthermore, since the heat capacity of the furnace wall increases, there is a problem that it takes a long time to raise and lower the furnace temperature. Alternatively, it is conceivable to use a heat insulating material with particularly good heat insulating properties, but such a heat insulating material is generally expensive and increases the equipment cost.

  The present invention has been made to solve the problems of the conventional heat treatment furnace. That is, the problem is to provide a heat treatment furnace that can improve the thermal efficiency of a high-temperature carburizing furnace and use the waste heat to save energy in the entire facility.

  The heat treatment furnace of the present invention made for the purpose of solving this problem is a first furnace for subjecting an object to a first heat treatment at a first heating temperature, and the object is lower than the first heating temperature. A second furnace that performs a second heat treatment at a second heating temperature, an inter-furnace wall that partitions the first furnace and the second furnace, and an outer wall that partitions the second furnace and the outside; A 1st furnace and a 2nd furnace are arrange | positioned adjacently through the wall between furnaces.

  According to the heat treatment furnace of the present invention, a certain amount of heat is transferred between these furnaces if a moderately heat-insulating wall is used between the first furnace and the second furnace. Furthermore, since the second furnace is a heat treatment at a temperature lower than that of the first furnace, an outer wall that is a partition from the outside can be made of a material having a normal heat insulating property. Furthermore, since the first furnace and the second furnace are partitioned by the inter-furnace wall, there is no possibility that atmospheric gas flows between them. Therefore, a carburizing furnace can be applied as the first furnace. As a result, the thermal efficiency of the high-temperature carburizing furnace is improved, and the heat treatment furnace can save energy by utilizing the waste heat.

Furthermore, in the present invention, each of the first furnace and the second furnace has a conveying member for conveying the object from the inlet to the outlet, and the outlet of the first furnace and the inlet of the second furnace are provided adjacent to each other. It is desirable that
If it becomes like this, the target object will be heat-processed in a 1st furnace, conveying the inside of a 1st furnace from an entrance to an exit by a conveyance member. Furthermore, since the inlet of the second furnace is adjacent to the outlet of the first furnace, it is easy to transfer from the outlet of the first furnace to the inlet of the second furnace. Therefore, the distance for moving the object is small, and can be transferred by, for example, a robot.

Furthermore, in the present invention, it is desirable that the first furnace is a carburizing furnace that performs a carburizing process, and the second furnace is a tempering chamber that performs a tempering process after the carburizing process.
Normally, tempering is performed at a lower temperature than carburizing. Therefore, the heat treatment furnace of the present invention can be applied to those performing these treatments.

  According to the heat treatment furnace of the present invention, the thermal efficiency of the high-temperature carburizing furnace can be improved, and the entire facility can be made energy-saving by utilizing the waste heat.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to a heat treatment furnace used in a heat treatment process included in a production process for producing metal parts such as gears.

  As shown in FIG. 1, the heat treatment furnace of this embodiment has a carburizing furnace 1, a quenching tank 2, and a cleaning machine 3. As shown in FIGS. 1 and 2, the carburizing furnace 1 is a composite furnace having a carburizing diffusion zone 11 and two return zones 12 adjacent to the left and right sides thereof. FIG. 1 is a sectional view seen from above, and FIG. 2 is a sectional view seen from the front of the carburizing furnace 1. Inside each zone 11, 12, a plurality of mesh belts 13 are provided at the top and bottom.

  In the carburizing furnace 1 of this embodiment, the boundary between the carburizing diffusion zone 11 and the return zone 12 is a furnace wall 15 made of heat insulating brick. Here, a heat-insulating brick having a thermal conductivity of 0.20 W / (m · K) and a thickness of 200 mm is used. An outer wall 16 made of rock wool is arranged between the return zone 12 and the outside. Here, rock wool having a thermal conductivity of 0.06 W / (m · K) and a thickness of 50 mm is used. Furthermore, the upper and lower surfaces of the carburizing furnace 1 are provided with heat insulating walls 17 having appropriate heat insulating properties.

  In this embodiment, the carburizing diffusion zone 11 and the return zone 12 can be controlled in temperature independently. For example, as shown in FIG. 3, the carburizing diffusion zone 11 can be controlled to 950 ° C., and the return zone 12 can be controlled to 150 ° C., respectively. However, the partition wall between them is only the furnace wall 15 having the above-described structure, and the heat insulating property of the heat insulating brick having a thickness of 200 mm is not extremely high. Therefore, a certain amount of heat is transferred from the carburizing diffusion zone 11 having a high temperature to the returning zone 12 having a low temperature.

When the temperature of each zone 11 and 12 is controlled to the above-mentioned level, on the outer surface of the inter-reactor wall 15 (on the return zone 12 side), the temperature exceeds 200 ° C. (for example, 217 ° C.). I know that Therefore, since the return zone 12 can obtain sufficient heat from the carburizing diffusion zone 11, a unique heating means for heating the inside is almost unnecessary. Even if it is provided, it can be very simple. Further, the temperature adjustment of the return zone 12 can be performed by, for example, the flow rate of the flowing gas. At this time, thermal energy is transmitted as shown by arrows in FIG. The amount of heat supplied from the carburizing diffusion zone 11 to the return zone 12 is about 733 W / m ² .

Further, the outside of the return zone 12 is insulated by the outer wall 16. The outside of the outer wall 16 is about 23 ° C., for example. At such a temperature, there is no problem even if the operator touches it, and it may be exposed. At this time, the returning zone 12 to the outside air, as indicated by arrows in FIG. 3, the fact that discharging the heat energy of approximately 162W / m ^2. The amount of this waste heat is very small as compared with the conventional one (about 494 W / m ² ; see problem column). Therefore, it is a heat treatment furnace with very good thermal efficiency.

  Further, since the carburizing diffusion zone 11 and the return zone 12 are partitioned by the inter-furnace wall 15, the atmosphere can be controlled independently. For example, the carburizing diffusion zone 11 may be an RX gas atmosphere, and the return zone 12 may be an air atmosphere. RX gas is a modified gas obtained by modifying natural gas or the like. The exhaust gas from the carburizing diffusion zone 11 is not returned to the zone 12. Therefore, heat can be reused by the heat conduction of the inter-furnace wall 15 even if the carburizing process using atmospheric gas and the returning process not using it. Further, the speed of the mesh belt 13 disposed in each of the zones 11 and 12 can be set independently.

  Next, a heat treatment procedure in the heat treatment furnace of this embodiment will be described. In the heat treatment furnace of this embodiment, each process is performed in the order of carburization, quenching, and tempering. The workpiece conveyed from the previous process is first carburized by the carburizing diffusion zone 11. In the carburizing diffusion zone 11, the upper end in FIG. 1 is an inlet 11a. The workpiece is carried into the carburizing diffusion zone 11 from the inlet 11a by a robot or the like and placed on the mesh belt 13.

  Then, it is conveyed by the mesh belt 13 in the horizontal direction as shown by the broken arrow in FIG. In the carburizing diffusion zone 11, the lower end in FIG. 1 is an outlet 11b. In this embodiment, the inside of the carburizing diffusion zone 11 is heated to about 900 ° C. to 1050 ° C. The workpiece is carburized while being sent to the outlet 11b by the mesh belt 13 over about 3 hours.

  Next, the quenching process is performed on the workpiece after the carburizing process. For this purpose, the workpiece is taken out from the outlet 11b of the carburizing diffusion zone 11 by a robot or the like. Subsequently, as shown by the dashed arrow in FIG. This quenching tank 2 is filled with water or oil. Here, oil is used. The workpiece is quenched by being inserted into this oil. The quenching tank 2 may be disposed near the outlet 11 b of the carburizing diffusion zone 11. When oil is used, the workpiece is generally cleaned by the cleaning machine 3 before tempering.

  A tempering process is then performed on the workpiece that has been quenched. For this purpose, it is placed on the mesh belt 13 in the return zone 12 by a robot or the like. The inlet 12 a of the return zone 12 is the lower end in FIG. 1 and is provided adjacent to the outlet 11 b of the carburizing diffusion zone 11. The mesh belt 13 in the return zone 12 is conveyed upward from the bottom in the figure as shown by the broken arrow in FIG. As a result, the workpiece is sent to the exit 12b, which is the upper end of the return zone 12 in the figure. The return zone 12 is controlled to about 150 ° C., for example, and the processing time is about 1 hour.

  Next, another form of carburizing furnace is shown in FIG. The carburizing furnace 20 has a cylindrical shape as a whole. Inside, a substantially cylindrical carburizing diffusion zone 21 on the inner peripheral side and a substantially cylindrical return zone 22 surrounding the outer periphery are formed. A plurality of turntables are arranged in each of the carburizing diffusion zones 21 and the return zone 22. The turntable in the carburizing diffusion zone 21 and the turntable in the zone 22 can be rotated independently of each other.

  Similarly to the carburizing furnace 1, the carburizing diffusion zone 21 and the returning zone 22 are partitioned by a furnace wall 25 made of heat-insulating brick having a thermal conductivity of 0.20 W / (m · K) and a thickness of 200 mm. ing. Further, an outer wall 26 made of rock wool having a thermal conductivity of 0.06 W / (m · K) and a thickness of 50 mm is provided on the outer peripheral side of the return zone 22. An open / close port 27 that can be opened and closed is formed in the inter-furnace wall 25. The outer wall 26 is formed with a door 28 that can be opened and closed.

  During the carburizing process, the temperature in the carburizing diffusion zone 21 is raised to, for example, 950 ° C., similarly to the carburizing diffusion zone 11 of the carburizing furnace 1. Further, the inside of the return zone 22 is, for example, about 150 ° C., similarly to the inside of the return zone 12 of the carburizing furnace 1. The workpiece is first placed on the turntable in the carburizing diffusion zone 21 on the back side and carburized while being rotated. Subsequently, the workpiece is taken out from the carburizing furnace 20 and subjected to a quenching process. Thereafter, it is placed on the turntable in the return zone 22 and tempering is performed.

  Furthermore, as another arrangement, as shown in FIG. 5, a carburizing furnace 30 in which a carburizing diffusion zone 31 and a return zone 32 are stacked one above the other may be used. A mesh belt 33 is provided inside each of the zones 31 and 32. When processing is performed, the mesh belt 33 in the carburizing diffusion zone 31 conveys the work from the front to the back in the figure, and the mesh belt 33 in the return zone 32 conveys the work from the back to the front in the figure. In this case, the quenching tank 35 should just be arrange | positioned near the exit of the carburizing diffusion zone 11 (back side in the figure). A return zone may also be provided in the upper part of the carburizing diffusion zone 31. Alternatively, return zones may be provided on the top, bottom, left and right of the carburizing diffusion zone.

  Alternatively, as shown in FIG. 6, a three-stage carburizing furnace 40 may be used. In this figure, a 950 ° C. zone 41 at the top, an 845 ° C. zone 42 at the middle, and a 150 ° C. zone 43 at the bottom are shown. A 150 ° C. zone or the like may be further provided on the 950 ° C. zone. In this case, in the relationship between the 950 ° C. zone 41 and the 845 ° C. zone 42, the 950 ° C. zone 41 corresponds to the first furnace, and the 845 ° C. zone 42 corresponds to the second furnace. In the relationship between the 845 ° C. zone 42 and the 150 ° C. zone 43, the 845 ° C. zone 42 corresponds to the first furnace, and the 150 ° C. zone 43 corresponds to the second furnace.

  Alternatively, as shown in FIG. 7, a cylindrical and stacking type carburizing furnace 50 may be used. Here, the carburizing diffusion zone 51 is arranged in the upper part and the zone 52 is arranged in the lower part. Further, a return zone may be arranged on the upper part of the carburizing diffusion zone 51.

  As described above in detail, according to the carburizing furnace of this embodiment, since the return zone is arranged on the outer peripheral side of the carburization diffusion zone, the waste heat from the carburization diffusion zone can be used in the return zone. Furthermore, between the carburizing diffusion zone and the return zone, it is only necessary to place an insulating brick wall made of heat-insulating bricks of an appropriate thickness, so there is no risk of increasing the size of the equipment and increasing equipment costs. The outer wall on the outer peripheral side of the return zone may be made of rock wool of moderate thickness. In addition, the amount of waste heat to the outside of the furnace can be reduced, resulting in good thermal efficiency.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
In each of the above forms, an insulating brick wall is placed between the carburizing diffusion zone and the return zone, and an outer wall made of rock wool is placed outside the return zone. Not limited to things. For example, these materials may be reversed, or the same material may be used. Further, for example, the heat treatment furnace of the present invention is not limited to the one used for the carburizing process and the returning process. For example, an annealing process and a tempering process may be performed. Further, depending on the processing content, there is a heat treatment that does not use the quenching tank 2. As long as it is a heat treatment furnace that performs only such treatment, the quenching tank 2 may not be provided.

It is a plane sectional view showing the carburizing furnace of this form. It is front sectional drawing which shows the carburizing furnace of this form. It is explanatory drawing which shows the temperature change and heat transfer amount inside and outside a carburizing furnace. It is explanatory drawing which shows the carburizing furnace of another form. It is explanatory drawing which shows the carburizing furnace of another form. It is explanatory drawing which shows the carburizing furnace of another form. It is explanatory drawing which shows the carburizing furnace of another form.

Explanation of symbols

1, 20, 30, 40, 50 Carburizing furnace 11, 21, 31, 41, 51 Carburizing diffusion zone 12, 22, 32, 42, 52 Return zone 15, 25 Outer wall 16, 26 Outer wall

Claims (3)

A first furnace for subjecting an object to a first heat treatment at a first heating temperature;
A second furnace for subjecting the object to a second heat treatment at a second heating temperature lower than the first heating temperature;
A furnace wall separating the first furnace and the second furnace;
An outer wall separating the second furnace from the outside,
The heat treatment furnace, wherein the first furnace and the second furnace are arranged adjacent to each other through an inter-furnace wall. In the heat treatment furnace according to claim 1,
Each of the first furnace and the second furnace has a transport member for transporting an object from an inlet to an outlet,
A heat treatment furnace characterized in that an outlet of the first furnace and an inlet of the second furnace are provided adjacent to each other. In the heat treatment furnace according to claim 1 or 2,
The first furnace is a carburizing furnace for carburizing;
The heat treatment furnace, wherein the second furnace is a tempering chamber for performing a tempering process after carburizing.

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