JP2007263480A - Muffle furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a muffle furnace capable of controlling atmospheric condition in a muffle body and manufacturing a product of an excellent quality. <P>SOLUTION: The muffle furnace consists of the muffle body 20 in which a treatment space L for conducting a thermal treatment to a workpiece W is formed, a heating part 21 for heating inside of the muffle body 20, a conveyance mechanism 15 for conveying the workpiece W and a gas heating mechanism 22 for heating atmospheric gas 50. The gas heating mechanism 22 provided near the muffle body 20 includes a gas supply chamber 25 with a gas supply hole part opening toward inside of the treatment space L and a gas supply source 27 for supplying the atmospheric gas 50 from outside of the muffle body 20 to the gas supply chamber 25 via a duct line 26. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a muffle furnace for subjecting a workpiece to a heat treatment such as sintering.

Generally, as a furnace for performing various heat treatments, a batch furnace or a continuous furnace for performing heat treatment while conveying a workpiece is known. On the other hand, in recent years, in a continuous furnace, a muffle furnace in which a certain atmosphere gas is sealed is frequently used in order to stably perform the heat treatment.
The muffle furnace includes a muffle body, a heating mechanism that heats the inside of the muffle body, a transport mechanism that transports the work to the muffle body, a discharge mechanism that discharges atmospheric gas in the muffle body to the outside, and a cooling work. A muffle furnace equipped with a cooling device is known.
Conventionally, in such a muffle furnace, gas supply mechanisms are provided between the cooling device and the muffle furnace and at several places in the cooling device to prevent outside air from entering the furnace and are carried into the muffle body by the transfer mechanism. A protective atmosphere necessary for heat treatment such as sintering of the workpiece is formed. (See Patent Document 1).
JP 2002-195754 A

By the way, in the above-mentioned conventional muffle furnace operated at a relatively low temperature, the heat transfer mechanism to the work is dominated by convection heat transfer, and the temperature distribution in the muffle body is also due to the drift of the atmospheric gas. There was a problem that it was easily disturbed and it was difficult to heat the workpiece uniformly.
For this reason, in a muffle furnace operated at a relatively low ambient temperature (about 500 ° C. or less), there has been a problem that heat treatment is not satisfactorily performed on the workpiece and quality varies.
In particular, when heat treatment is performed at a constant temperature for a certain period of time, the temperature of a predetermined section in the muffle body needs to be equalized, but depending on the flow of atmospheric gas, a temperature deviation may occur in the muffle body. There is a problem that it is difficult to keep the section in a soaking state, and it is difficult to satisfy a predetermined heat treatment condition at a constant temperature.

  The present invention has been made in consideration of such circumstances, and its purpose is to control the atmospheric conditions in the muffle body, and to maintain the inside of the muffle body in a soaking state. An object of the present invention is to provide a muffle furnace that can perform the above-described process well.

In order to achieve the above object, the present invention proposes the following means.
The invention according to claim 1 is a muffle body in which a processing space for heat-treating a workpiece is formed, a heating unit that heats the inside of the muffle body, and conveyance that conveys the workpiece in the one direction in the muffle body. And a gas heating mechanism that heats the atmospheric gas in the processing space. The gas heating mechanism is disposed in the vicinity of the muffle body and has a gas supply hole that opens toward the processing space. And a gas supply source for supplying atmospheric gas to the gas supply chamber from the outside of the muffle body through a pipe line.

  According to the muffle furnace according to the present invention, the atmosphere gas is directly supplied from the gas supply chamber in the portion of the processing space in the muffle body where the gas supply chamber is provided. And soaking is performed on the workpiece.

  According to a second aspect of the present invention, in the muffle furnace according to the first aspect, at least a part of the pipeline of the supply mechanism is disposed in the vicinity of the heating unit, and the heating unit is disposed in the pipeline. It also serves as a heating part for the atmospheric gas.

  According to the muffle furnace according to the present invention, the heating mechanism heats the atmospheric gas in the pipe line, and the atmospheric gas that has reached substantially the same temperature as the furnace control temperature passes through the gas supply chamber into the muffle body. Supplied.

    According to a third aspect of the present invention, in the muffle furnace according to the first or second aspect, the gas supply chamber is provided on at least one of an upper side and a side of a portion of the muffle main body that is soaked in the tropical zone. In addition, the gas supply hole is disposed at a position corresponding to the work in the soaking zone of the processing space, and while maintaining the furnace pressure constant while suppressing the flow rate of the atmospheric gas, the work has a uniform temperature distribution. It is characterized by doing.

  According to the muffle furnace according to the present invention, the gas supply chamber is provided at least either above or on the side of the muffle body which is set to be soaking, so that the temperature is substantially the same as the soaking control temperature. Ambient gas is sprayed uniformly over the entire workpiece at a constant flow rate, and the workpiece has a uniform temperature distribution, so that a uniform temperature treatment is performed. Since the furnace pressure fluctuation is minute, there is no intrusion of outside air into the furnace, and stable operation can be performed while reducing the consumption of the atmospheric gas.

  According to the present invention, the atmospheric conditions in the muffle body can be controlled, the inside of the muffle body can be kept in a soaking state, and a product that has been well heat-treated can be reliably manufactured. Can do.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view of the heat treatment facility according to the present embodiment.
The heat treatment facility 10 includes a muffle furnace 11, a cooling device 12, a discharge mechanism 13, and a transport mechanism 15 that transports the workpiece W.
As shown in FIG. 2, the muffle furnace 11 includes a support frame 16 provided on the floor and an outer shell body 17 provided on the support frame 16 and having a rectangular cross section perpendicular to the conveyance direction of the workpiece W. And.
In addition, the cross section perpendicular | vertical to the conveyance direction of the workpiece | work W of the outer shell 17 may be circular.

A muffle body 20 having a rectangular or semicircular cross section, a heating unit 21 provided outside the muffle body 20, and a gas heating mechanism 22 are provided inside the outer shell body 17.
As shown in FIG. 3, the muffle body 20 is composed of an upper wall portion 20a, a side wall portion 20b, and a lower wall portion 20c, and the inside of the muffle body 20 is a processing space L in which heat treatment is performed on the workpiece. Yes.
The heating unit 21 includes an upper heater 24A and a lower heater 24B. The heater 24A is above the muffle body 20 and the lower heater 24B is below the muffle body 20 with respect to the conveying direction of the workpiece W. It extends vertically and is supported in the outer body 17.

 As shown in FIG. 2, the upper heater 24 </ b> A extends from the rear side in the transport direction (workpiece outlet side) to the center portion in the muffle main body 20 and from the central portion to the front side in the transport direction (workpiece carry-in side). Are arranged at substantially equal intervals, and the interval between the rear side in the transport direction and the center portion in the muffle body 20 is narrower than the interval between the center portion and the front side in the transport direction. . The lower heater 24B is also arranged similarly to the upper heater 24A.

The gas heating mechanism 22 includes a pipe line 26 disposed on the upper surface or side surface in the vicinity of the muffle main body 20, and a gas supply source (gas supply mechanism) 27 that supplies the atmosphere gas 50 to the pipe line 26. .
In FIG. 5, the gas supply chamber 25 includes a plate 25 a disposed horizontally above the processing space L in the muffle body 20, a wall portion 25 b provided on the front side in the transport direction, and a rear side in the transport direction. It is comprised from the wall part 25c provided in the upper wall part 20a, and the side wall part 20b.

As shown in FIG. 4, a plurality of gas supply holes 28 are formed in the plate 25 a, and the atmospheric gas 50 that is uniformly heated with respect to the workpiece to be conveyed is supplied from above the processing space L. (See FIGS. 3 and 5).
In particular, the gas supply hole 28 in the soaking zone L1 of the processing space L is preferably formed at a position corresponding to the workpiece W (for example, above the workpiece W).
The gas supply hole 28 can be formed either above or laterally of the processing space L, but is preferably formed above.

For example, as shown in FIG. 2, the pipe line 26 is disposed in the vicinity of the upper heater 24A, and as shown in FIG. 5, the pipe line 26 is sequentially folded in the width direction of the upper wall portion 20a to be in a meandering state. Is arranged.
A gas supply source 27 that supplies an atmospheric gas 50 such as nitrogen gas is connected to the end of the conduit 26 on the front side in the transport direction. In FIG. 2, the pipe line 26 constitutes a heat exchanger that preheats the atmospheric gas 50 by the heat from the upper heater 24 </ b> A, and the discharge mechanism 13 is provided on the front side in the transport direction of the muffle furnace 11.

Next, the effect | action of the heat processing equipment 10 comprised in this way is demonstrated.
As shown in FIG. 2, in the muffle furnace 11, the gas supply source 27 supplies the atmospheric gas 50 to the pipeline 26 from the front side in the transport direction.
The upper heater 24 </ b> A heats the atmospheric gas 50 flowing through the pipe line 26. As shown in FIG. 3, the heated atmospheric gas 50 is supplied into the gas supply chamber 25 and supplied into the processing space L in the muffle body 20 from the gas supply holes 28 formed in the plate 25a.

In FIG. 2, the upper heater 24 </ b> A and the lower heater 24 </ b> B are arranged at an optimal interval, and the atmospheric gas 50 is heated and heated to the furnace control temperature.
Similarly, the workpiece reaches the maximum temperature and enters the processing space L, where the uniformly heated atmospheric gas 50 is sprayed.
As a result, a turbulent flow is formed in the processing space L, and a soaking zone L1 in which the temperature of the workpiece is maintained within a predetermined temperature deviation is obtained.

  The atmospheric gas 50 ejected from the gas supply chamber 25 into the processing space L flows through the muffle body 20 to the front side in the transport direction, and is discharged from the discharge mechanism 13 to the outside of the furnace.

The transport mechanism 15 passes the workpiece W through the muffle body 20 installed inside the muffle furnace 11. At this time, the workpiece W is heated and heated.
At this stage, impurity gas may be generated from the workpiece W. The generated impurity gas is accompanied by the atmospheric gas 50 and is discharged from the discharge mechanism 13.
Then, the workpiece W is cooled by the cooling device 12.

In such a heat treatment facility 10, in the soaking zone L <b> 1 in the processing space L, the gas supply hole 28 is disposed at a position corresponding to the workpiece W from the front side in the transport direction to the rear side in the transport direction. Therefore, the temperature deviation of the atmospheric gas 50 can be suppressed, and the workpiece W can be heat-treated in an isothermal state for a predetermined time.
Further, since the gas supply hole portion 28 is disposed at a position corresponding to the workpiece W in the soaking zone L1 of the processing space L, the heat loss due to heating is small, so that the atmosphere gas 50 is suppressed to the minimum flow rate, and the furnace It is possible to keep the internal pressure constant.

  The various dimensions of the heat treatment equipment 10 according to this embodiment are such that the size of the plate 25a is 485 mm × 1500 mm, the size of the gas supply hole 28 is 10 mm, and the plate of the gas supply hole 28 The opening ratio with respect to 25a is 0.6% or more and 2.0% or less, and the gas supply holes 28 are provided in 95 places (5 places × 19 rows) in the plate 25a. Further, nitrogen gas is used as the atmosphere gas 50, and the ejection speed of the atmosphere gas 50 is set to 1 m / S or more and 2 m / S or less.

 As another example, the size of the plate 25a is 420 mm × 3000 mm, the size of the gas supply hole 28 is 8 mm in diameter, and the gas supply hole 28 is 175 places (5 places × 35 in the plate 25a). The opening ratio of the gas supply holes 28 to the plate 25a is 0.6% or more and 2.0% or less. Further, dry air is used as the atmosphere gas 50, and the ejection speed of the atmosphere gas 50 is set to 1 m / S or more and 2 m / S or less.

 Here, the opening ratio is obtained based on the economic efficiency of the flow rate of the atmospheric gas 50 while properly forming the jet from the gas supply hole 28. As for the ejection speed, when the distance between the plate 25a and the workpiece W is 80 mm or less, the need for ventilation in the furnace such as prevention of intrusion of outside air by the furnace pressure stabilization and removal of impurity gas generated in the furnace, and reduction of the use amount of the atmospheric gas 50 It is selected from the economy.

 In these cases, in a continuous muffle furnace operated at an in-furnace control temperature of 400 ° C. or less, the temperature deviation of the temperature equalizing body L1 can be within ± 5 ° C. This is effective because the inside of the muffle body 20 can be well ventilated by preventing the outside air from entering the inside.

  In the said embodiment, although the case where the heat processing equipment 10 was comprised from the one muffle furnace 11 was demonstrated, the heat processing equipment 10 may be comprised from the 2 or more muffle furnace 11, and about a cooling device. Can be arbitrarily combined.

  Moreover, in the said embodiment, although the heating part 21 demonstrated the case where it comprised from the upper heater 24A and the lower heater 24B, you may use the heater heated from the side wall part 20b side, and a side wall part. It is also possible to configure the heating unit 21 by arbitrarily combining a heater that heats from the 20b side, an upper heater 24A, and a lower heater 24B.

  Moreover, in the said embodiment, although the case where the gas supply chamber 25 was provided above the part made into the soaking zone L1 of the muffle body 20 was demonstrated, the gas supply chamber 25 is soaking zone L1 of the muffle body 20 It is possible to provide for either or both of the upper side and the side.

  Moreover, in the said embodiment, although atmospheric gas 50 was supplied from the conveyance direction front side of the pipe line 26, and demonstrated the case where it flowed to the conveyance direction back side, distribution | circulation of the atmospheric gas 50 in the pipe line 26 is carried out. It is possible to adopt either a configuration from the front side in the transport direction to the rear side or from the rear side in the transport direction to the front side.

  In the muffle furnace operated at 500 ° C. or less according to the present invention, the atmospheric conditions in the muffle body can be controlled, the work can be kept in a uniform temperature state, and the heat treatment is performed well. Since the product can be manufactured, industrial applicability is recognized.

1 is a side sectional view of a continuous muffle furnace according to a first embodiment of the present invention. It is a sectional side view of the muffle furnace of the continuous muffle furnace shown in FIG. It is sectional drawing of the direction perpendicular | vertical to the conveyance direction of the continuous muffle furnace shown by FIG. It is a bottom view of a gas supply chamber. It is a perspective view of a heat exchanger.

Explanation of symbols

W Work L1 Soaking area 11 Muffle furnace 20 Muffle body 21 Heating unit 22 Gas heating mechanism 24A Upper heater (heating unit)
24B Lower heater (heating unit)
25 Gas supply chamber 26 Pipe line 27 Gas supply source (gas supply mechanism)
28 Gas supply hole 50 Atmospheric gas

Claims (3)

A muffle body in which a processing space for heat-treating the workpiece is formed, a heating unit for heating the inside of the muffle body, a transport mechanism for transporting the workpiece in the one direction in the muffle body, and an atmosphere in the processing space A gas heating mechanism for heating the gas,
The gas heating mechanism is disposed in the vicinity of the muffle body, and includes a gas supply chamber having a gas supply hole that opens into the processing space, and the gas supply chamber from outside the muffle body via a conduit. A muffle furnace comprising a gas supply source for supplying atmospheric gas to the furnace. In the muffle furnace according to claim 1,
A muffle furnace, wherein at least a part of the pipeline of the supply mechanism is disposed in the vicinity of the heating unit, and the heating unit also serves as a heating unit for the atmospheric gas in the pipeline. In the muffle furnace according to claim 1 or 2,
The gas supply chamber is provided at least either above or on the side of the muffle body that is leveled, and the gas supply hole is disposed at a position corresponding to a work in the leveled zone of the processing space. And
A muffle furnace characterized in that the work has a uniform temperature distribution while maintaining the furnace pressure constant while suppressing the flow rate of the atmospheric gas.

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