JPS583192B2 - Atmosphere heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an atmosphere heating furnace, and more particularly to a heating furnace for sintering aluminum powder metallurgy parts.

Conventionally, a hump pack type atmosphere heating furnace as shown in Fig. 1 has been used to sinter aluminum powder metallurgy parts in order to maintain a particularly high purity atmosphere. It is conveyed from the end 2 through the dewaxing section 3, the sintering section 4, and the cooling section 5 to the outlet end 6 by an endless mesh belt or chain conveyor 7, and passes through the dewaxing section 3 and the sintering section 4 in sequence. The heating coils 8 and 9 of the nichrome wire are used to heat the wire to a predetermined temperature for dewaxing and sintering, and then the water cooling jacket 1 is heated while passing through the cooling section 5.
0 cooling water and taken out from the outlet end 6.

Reference numeral 11 indicates a conveyor drive roller driven by a variable motor (not shown), and 12 indicates an indoor roller.

Then, the positions of the dewaxing part 3 and the sintering part 4 are adjusted to the inlet end 3,
It is placed at a higher position than the outlet end 6.

In order to maintain a predetermined gas atmosphere inside the heating furnace configured as described above, an atmospheric gas inlet 13 such as N2, H2 gas, etc. is provided at the furnace outlet end. In the dewaxing section 3, the wax vapor evaporated from the article to be treated is transferred to the conveying direction 1 of the article to be treated 1.
6 and in the direction opposite to arrow 17, and a gas curtain or frame curtain made of N2 gas is provided at the furnace inlet end 2 and outlet end 6, respectively, to prevent outside air from entering the furnace.

Atmospheric gas reaches a high temperature especially in the sintering section 4, so it becomes light and tends to accumulate in the sintering section 4 located at a high place.On the other hand, the outside air that enters from the inlet end 2 or the outlet end 6 is low temperature and therefore heavy. is difficult to enter.

This makes it possible to maintain an extremely high purity gas atmosphere having a dew point of -40 DEG C. or lower, which is required in the sintering section 4 in an N2, H2 and decomposed NH3 gas atmosphere.

In the conventional atmosphere heating furnace configured as described above, the furnace outlet end 6 on the sintering section 4 side is always open, so outside air is rarely allowed to enter when the article to be processed 1 is taken out from this open outlet end. It has been difficult to keep the dew point of the sintered part 4 stable at -40°C or lower at all times because it may get caught up in the furnace.

Therefore, in order to keep the dew point below a predetermined temperature, it was necessary to increase the amount of atmospheric gas supplied.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, and by providing a structure in which the outlet end of the atmosphere heating furnace can be closed, it is possible to maintain a high purity atmosphere in the furnace in a much more stable state than in the past. We are trying to provide an atmosphere heating furnace that allows for

Therefore, the atmosphere heating furnace according to the present invention is characterized in that an outside air shielding outlet inclined passageway is provided at the furnace outlet end, and an outlet shutter is provided in this inclined passageway, which is opened and closed in response to passage of the article to be processed.

Further, in carrying out the present invention, by providing a gas exchange chamber at the outlet that is opened and closed by the outlet shutter, the flow rate of the introduced gas required to maintain the sintered part at the required atmospheric dew point can be further reduced.

The invention will now be explained with reference to the drawings.

2 through 4 illustrate preferred embodiments of the present invention, in which parts similar to the conventional atmosphere furnace shown in FIG. 1 are designated by the same reference numerals as described in connection with FIG.

As shown in FIG. 2, in the atmosphere heating furnace according to the present invention,
A separate endless screen belt conveyor or chain conveyor 20.2 is provided in the dewaxing section 3 and the sintering section 4 respectively.
1, each of the drive rollers 22, 23 of these endless conveyors 20, 21 is driven by a separate variable speed motor (not shown) to vary the speed of each endless conveyor as desired, An optimal combination of dewaxing and sintering time is obtained depending on the shape, composition, density, etc. of the article 1 to be treated.

As described above, since a separate endless conveyor 21 is used to transfer the article 1 to be processed to the sintering section 4, when this endless conveyor 21 is passed outside the furnace as in the prior art described above, an endless conveyor 21 is used. The conveyor 21 has the disadvantage that the purity of the atmospheric gas is deteriorated, and in order to prevent this, the endless conveyor 21 passing through the sintering section 4 is kept in the furnace atmospheric gas at all times without contacting the outside air. .

For this reason, as shown in FIG.
The upper hearth 24 has a heavy bottom structure, and an appropriate communication hole 26 is provided in the upper hearth 24 so that the atmosphere in the upper and lower furnaces becomes almost equal through the communication hole 26.
a, 21a and return parts 20b, 21b to the upper hearth 2
4 by guide rollers 27 and 28, respectively.

Although the guide roller 27 at the inlet end of the dewaxing section endless conveyor 200 is installed outside the furnace, the dewaxing section endless conveyor 20
guide roller 27 at the outlet end of the sintering section endless conveyor 210 and guide roller 2 at the inlet end and outlet end of the sintering section endless conveyor 210
8, 28 are provided at the boundary between the dewaxing section 3 and the sintering section 4, and an in-furnace pit 29 is provided at the furnace outlet end 6.
Each is provided inside.

An outside air shielding inclined passage 31 is connected to the furnace outlet end 6, and a normally closed Roshutter 32 is attached to the outlet end of this inclined passage 31.
An actuator 33 such as a hydraulic cylinder or an air cylinder is connected to the outlet shutter 32 so that it can open and close, and an atmospheric gas introduction pipe 34 is also connected to the inclined passage 31.

A limit switch 3 activated by the article to be processed sliding down the inclined passageway 31 at the front and back positions of the outlet shirtter 32
5.36 is provided, and when the limit switch 35 is activated by the article to be processed, the cutoff valve 3 of the atmospheric gas introduction pipe 34 is provided.
After opening 7, the actuator 33 is actuated to open the outlet shutter 32, and when the limit switch 36 is actuated by the article to be processed, the actuator 33 is actuated to close the outlet shutter 32 and then close the shutoff valve 37. The control circuit 38 is configured and connected.

When operating the atmosphere heating furnace configured as described above, the speeds of the dewaxing section conveyor 20 and the sintering section conveyor 21 are changed depending on the shape, size, material, density, etc. of the article to be processed to obtain the optimum dewaxing time. The article to be processed is dewaxed in the dewaxing section 3, sintered in the sintering section 4, and cooled in the cooling section 5. and comes into contact with the limit switch 35.

At the same time as the limit switch 35 operates, the cutoff valve 37 opens, and N2 is introduced into the inclined passage 31 from the atmospheric gas introduction pipe 34.
The outlet shutter 32 is opened by the actuator 33 in a state where a large amount of gas flows in and the atmosphere can be prevented from entering the furnace, so that the article to be processed is transferred to the outlet shutter 3.
2 and taken out of the furnace.

After the article to be processed passes through the outlet shutter 32, the limit switch 36 is operated and closed, and the cutoff valve 37 is also closed to stop gas inflow from the atmospheric gas introduction pipe 34, thereby completing one cycle.

By combining the limit switches 35 and 36, the ffl shutter 32, and the shutoff valve 37, the furnace is a continuous furnace with both ends open only for a short time when the article to be processed passes through the shutter 32, but other than that, only the inlet end is open. It is of an open end type with a metal end closed type, which makes it easy to maintain the dew point in the sintered part 4, and also significantly reduces the amount of gas consumed.

As shown in Fig. 2, it is possible to secure a considerable atmospheric dew point even with a one-end closed system in which only one shutter 32 is provided on the furnace outlet side, and there is no practical problem. If a stable atmosphere is required, a gas exchange chamber system equipped with a double shutter mechanism as shown in FIG. 4 is suitable.

In the row shown in FIG.
9.40 are spaced apart at appropriate intervals, and both shirts 3
9. A gas exchange chamber 41 is defined for 40 hours, and a small-diameter gas introduction pipe 42 and a gas discharge pipe 43 are connected to constantly reflux N2 gas into this gas exchange chamber 41. A large-diameter gas introduction pipe 44 capable of introducing N2 gas is connected, and a shutoff valve 46 is provided on this large-diameter gas introduction pipe 44.

Limit switches 47 are installed before and after the gas exchange chamber inlet shutter 390 and before and after the gas exchange chamber outlet shutter 400, respectively.
, 48 and 49, 50 are provided so as to be actuated by contact with the articles to be treated sliding down the inclined passage 31, while a compressor (not shown) is connected to the compressor 39, 40 via an electromagnetic three-way valve 67, 68. When the limit switch 47 is closed, the shutter 39 is opened, when the limit switch 48 is closed, the shutter 39 is closed, and when the limit switch 49 is closed, the shutoff valve 46 is opened and the shutter 40 is opened. The control circuit is configured such that the actuator 52 connected to the button is actuated to open the shutter 40, and when the limit switch 50 fails to close, the shutter 40 is closed. Specific examples of this control circuit are shown in FIGS. 5 and 6.

E1 is a power source, to which the normally closed contact 48b of the limit switch 48 is connected in series with the relay R1 and the normally open contact 47a of the limit switch 47, and the normally open contact Rl a of the relay R1 is connected in parallel with the limit switch 47. −
1 connected to electric circuit A, relay R2 and delay relay R
D in parallel with the normally closed contact 50b of the limit switch 50 and the normally open contact 49 of the limit switch 49
A and a circuit in which the normally open point R2a-1 of the relay R2 are connected in parallel, and a circuit B in which the circuit is connected in series are connected in parallel.

On the other hand, the three-way valve 67 and the normally open contact R1 of the relay R1 are connected to the power supply E2.
a-2, solenoid cutoff valve 46 and relay horse normally open contact R2 a
-2. Connect the three-way valve 68 and the normally open contact RD& of the continuous relay RD in parallel to each other.

The delay relay RD is set to the time required for the shutoff valve 46 to open and for the space between the shutters 39 and 40 to be replaced with N2 gas, as will be described later.

By providing the above-mentioned control circuit, before the article to be processed that has entered the inclined passageway 31 from the furnace outlet end 6 contacts the limit switch 47, the shutter shutters 39, 40 and the shutoff valve 46 are all closed, and the gas exchange chamber is closed. The inside of 41 is maintained in an N2 gas atmosphere by the N2 gas introduced through the gas introduction pipe 42 and discharged through the gas exhaust pipe 43.

In this state, when the limit switch 47 is closed due to the object to be processed sliding down the inclined passageway 31 contacting the limit switch 47, the relay R1 is energized and the Rl
a-1 is closed and this electric circuit AIJ is maintained.

At the same time, the contact R1a-2 closes, the three-way valve 67 opens, the actuator 51 operates, the gas exchange chamber inlet shutter 39 opens, and the article to be treated enters the gas exchange chamber 41.
Next, limit switch 48 is contacted, which causes contact 4
8b is opened, relay R1 is demagnetized, R'ia-'z is opened, three-way valve 67 is closed, the air in actuator 51 is released to the atmosphere, and shutter 39 is closed.

Next, when the article to be processed contacts the limit switch 49 and the contact 49a closes, v 7 R2 is energized, the shutoff valve 46 opens, and a large amount of N2 gas is introduced into the gas exchange chamber 41, and this state is Since the contact point R2 a-1 is closed, it is self-held.

Also, at the same time as the limit switch 49 closes, the delay relay RD is energized, and after the space between the shutters 39 and 40 is replaced with N2 gas, the contact RDa is closed, the three-way valve 68 is opened, and the actuator 52 is actuated to open the gas exchange chamber outlet. shirtta 4
0 opens.

As a result, the article to be processed leaves the gas exchange chamber 41 and comes into contact with the limit switch 50.

When the limit switch 50 is activated, the contact 5
0b opens, and both the relay R2 and the delay relay are demagnetized, so the contacts R2 a -2 and RD2 open, the three-way valve 68 closes, and the air in the actuator 52 is released to the atmosphere, the shutter 40 is closed, and the cutoff valve 46 is opened. is closed, thus completing one cycle.

7 to 11 show another embodiment of the gas exchange chamber system equipped with a double shutter mechanism, and in this example, an inclined outlet passage 31 provided at the end of the furnace, and an inlet end and an outlet end thereof. A gas exchange chamber 55 is defined by the provided door or shutter shutter 53,54.

An inclined plate 56 is rotatably provided between the outlet end of the sintering section conveyor 21 and the inlet end of the gas exchange chamber 55, with one end of the inclined plate 56 being pivotally supported by a pivot shaft 57. The inlet shutter 53 is connected to the shutter 53 as described below and is always in the open position, so that the free end of the inclined plate 56 is engaged with the lower side of the inlet end of the gas exchange chamber 55 and is protected from the sintering part conveyor 21. The article to be treated is configured to slide down the inclined plate 56 and enter the gas exchange chamber 55.

The entrance door or shutter 53 and the exit door or shutter 54 are respectively attached to a rotating shaft 59.59' as shown in FIGS. Supporting and rotating shaft 59.
Racks 62 and 62' meshed with pinions 61 and 61' fixed to one end of 59' are operably connected by air cylinders 63 and 63', respectively.

The air cylinders 63 and 63' are connected to a high-pressure air source and to the gas exchange chamber 55 through electromagnetic three-way valves 70 and 70, respectively.
An inlet pipe 64 and an outlet pipe 65 for atmospheric gas such as gas are provided, and a solenoid valve (not shown) of the inlet pipe 64 is kept open.
The solenoid valve 71 of the discharge pipe 65 is normally closed.

Further, a phototube-type limit switch 66 is provided in the gas exchange chamber 55 and is actuated by the article to be treated sliding down the inclined path.

Hereinafter, the armature circuit including the shirt shutters 53, 54, the three-way valves 70, 7σ, etc. will be explained based on FIGS. 10 and 11.

When energized, the first normally open contacts 72a-1, 72 for a predetermined time
Timer 72 that closes a-2, 73a-3, 72a-4
A circuit C in which the timer 72 is connected in series with a circuit in which the contacts 72 and 66 are connected in parallel to the contact 66a which is closed when the contacts 72 and 66 are activated.
, a timer 73 that closes the normally open contact 73a for a second predetermined time when energized, and a delay circuit 74 that delays operation for a third predetermined time.
and the contact 72a-2 of the timer 72 are connected in series. and the contact 7 of the delay relay 75 and timer 72, which closes the contact 75a after a fourth predetermined time has elapsed when energized.
2 a - 3 are connected in series to the power supply E.
3 in parallel.

On the other hand, an electric line F1 in which the contact 72a-4 and the electromagnetic three-way valve 70 are connected in series, an electric line G1 in which the contact 73a and the three-way valve 70' are connected in series, and an electric line H in which the contact 75a and the electromagnetic valve 71 are connected in series. are connected in parallel to the power supply E4.

Next, the operation of the apparatus configured as described above will be explained.

The article to be processed is passed through the entrance shaft 53 which opens through the inclined plate 56.
It slides down through the gas exchange chamber 55.

Here, the photoelectric limit switch 66 detects the article to be processed and the contact 66a closes.

Therefore, timer T2 operates and each contact 72a1 to 72a
．． Close.

Therefore, even if the article to be processed passes through the limit switch 66, the contact 72a-1 remains closed, so the timer 72 remains closed.
is activated.

At the same time, the three-way valve 70 opens and high pressure air flows into the air cylinder 7.
0, the rack 62 is pushed out, the pinion 61 integrated with the rotating shaft 59 rotates, and the inlet shutter 53 closes the inlet of the gas exchange chamber 55.

Then, after the first predetermined time has elapsed, that is, the entrance shirt shutter 53
After the timer 73 is completely closed, the delay circuit 74 is activated.
is activated, the contact 73a closes and the three-way valve 70' opens, supplying high pressure air to the air cylinder 63' to pull back the rack 6z, and the pinion 61 The rotary shaft shutter 54 is opened according to the rotation of '.

After the second predetermined time has elapsed, the contact 73a opens and the three-way valve 70'
When the air cylinder 63' is closed, the air inside the air cylinder 63' is released to the atmosphere.

Therefore, the shirt flap 54 is closed again.

On the other hand, after the 40th predetermined time after the timer 72 is activated,
That is, after the time elapses until the shirt shutter 54 closes, the delay relay 75 is energized and the contact 75a closes.

Therefore, the solenoid valve 71 opens, and the gas introduced into the gas exchange chamber 55 from the gas introduction pipe 64 causes the gas exchange chamber 55 to
The outside air that has entered the interior is expelled from the gas exhaust pipe 65.

Next, after a first predetermined time has elapsed, that is, the time from when the timer 72 is energized to when the gas replacement in the gas replacement chamber 55 is completed, the contacts 72a-1 to 72a-4 open, and the timers 72, 7
3. The delay relay 75 is deactivated and the entrance shutter 53
opens, the outlet shutter 54 closes, and the solenoid valve 71 returns to its closed state, that is, its original state, completing one cycle.

Hereinafter, the present invention will be explained with reference to examples.

Example 1 An aluminum powder metallurgy part was sintered using a continuous aluminum sintering furnace having the structure shown in FIG.

The main specifications of the aluminum sintering furnace used are shown below.

Furnace total length: 8000mm sintered material placement section 1500mm dewaxing section (nichrome wire heating) 2000mm sintering section
2000mm water cooling section 10
00mm Air cooling and inclined passage section 1500mm
Conveyor type: Mesh belt drive speed for both dewaxing section and sintering section: 10 to 200 mm/mi
n Matsuful dimensions: 150mm x 200trr
m Belt width: 180wn Mixed powder molding conditions are mixed powder composition (wt%) Al-4.4Cu-0.5Mg-0.8Si 1.5
Wax molding pressure 5 ton/cm2 Molded shape ISO 2740 tensile test piece (6 mm thickness), sintering was performed in ammonia decomposition gas After various examinations of the sintering conditions, the conditions that yielded the highest strength were the set temperature of the burn-off section. 400℃〃 Mesh belt speed 150 mm/min Set temperature of sintering part 600℃〃 Mesh belt speed 100 mm/min, Tensile strength is 29.5h/7I on average after T6 treatment
IJ was shown.

This is done in a conventional furnace as shown in Figure 1 (the dimensions of each part are the same as described above, except for the sloped part), with the same set temperature in the dewaxing part and the sintering part, and a belt speed of 150 t.
When flowing at rtm/min, the sintering time is slightly shorter, so the average tensile strength after T6 treatment is 25.
It can only reach up to 4 kg/vtit.

On the other hand, when sintering is performed at 100 rrrm/min, it takes 10 min from the time the material to be sintered enters the furnace until it comes out.
However, productivity decreases because it takes time.

Furthermore, in the case of the furnace of the present invention shown in Fig. 2, a total flow rate of 5 m3/hr is sufficient to supply gas at -60°C and keep the dew point of the sintering section 4 below -40°C. There was no change in the dew point even when the article to be treated 1 was taken out.

Note that the inlet end 2 side is always open, and there is a possibility that outside air may enter the furnace when the article 1 is being sintered, but since the atmospheric gas flows from the inlet 13 toward the inlet end 2, sintering is not possible. It will never reach part 4.

Implementation row 2 Using a continuous aluminum sintering furnace having the same structure as shown in FIG. 2 as in implementation row 1, mixed powder composition (wt%) Al-2.5%Cu-0.6%Mg-0.5 %Si molding pressure: 5 ton/cm2 After sintering the blank material with a shape of 130φ x 40H in a N2 gas atmosphere, JIS No. 7 test pieces were cut out from the center and periphery, and T6
The strength after treatment was examined.

As a result of various preliminary experiments, the conditions that yielded the highest strength were: Dewaxing section temperature set at 400°C Mesh belt speed 10 mm/min Sintering section set temperature Mesh belt speed 40 mm/min After T6 treatment The average strength was 34 kg/mm2.

When this is sintered in a conventional furnace of the type shown in Fig. 1, the belt speed is constant, so as mentioned above, the mesh belt speeds in the dewaxing section and the sintering section are set differently to create the optimal mesh belt. You can't get a combination of speeds.

For example, the belt speed is I O rran/m i
When n is constant, dewaxing can be achieved sufficiently, but if the sintering time is too long, the sintered structure becomes coarse and the tensile strength after T6 treatment is 26@/yr on average? decreases to t.

Furthermore, it has a production disadvantage in that it takes a little more than three hours for one cycle from charging the material to be sintered into the furnace to completing sintering.

If the belt speed is kept constant at 40 mm/min, wax enters the sintering section without being sufficiently dewaxed due to insufficient dewaxing time, and wax vapor enters the sintering section, reducing the purity of the sintering atmosphere. Average strength after T6 treatment is 23kg/
It is only up to about mm2.

Also, even if the process is continued, the dew point of the sintered part 4 is always -40℃.
It was kept below.

When the dew point of the raw material N2 gas supplied from the gas inlets 13 and 14 is kept constant at -60°C, the following flow rate is required to maintain the atmospheric dew point in the sintering zone at -40°C or less.

A) Furnace of the present invention with one end closed (Fig. 2) → 9 m3/hr B) Furnace of the present invention with a combination of one end closed and a gas exchange chamber → 6 m
3/hr (combination of FIGS. 2 and 4) Compared to the conventional furnace with both ends open, the one-end closed furnace of the present invention has the advantage of much lower gas consumption.

Furthermore, the furnace of the present invention, which combines a one-end closed type furnace with a gas exchange chamber, can consume even less gas.

Moreover, in case a), the atmospheric dew point of the sintering zone is -4
Although it is limited to about 5'C, in the case of b), it is possible to lower the atmospheric gas dew point to about -53℃, so this method is suitable for sintering that requires a higher purity atmosphere. I made sure of that.

According to the present invention, by configuring the furnace outlet end to be closed, the sintered part could always be stably maintained at a required dew point.

．． Therefore, the required gas consumption is significantly lower, the thermal economy is excellent, and the atmosphere inside the furnace can be easily maintained at a higher purity than before, which significantly reduces the occurrence of defective products and improves yield. .

In particular, by providing a gas exchange chamber at the outlet of the article to be processed, it can be closed to completely block the inflow of outside air from the furnace outlet end, making it easy to maintain the purity of the atmosphere and reducing atmospheric gas consumption. can be further reduced.

[Brief explanation of drawings]

Fig. 1 is a diagrammatic longitudinal sectional view of a sintering atmosphere heating furnace of conventional structure, Fig. 2 is a diagrammatic longitudinal sectional view of a sintering atmosphere heating furnace according to the present invention, and Fig. 3- is a diagrammatic longitudinal sectional view of a sintering atmosphere heating furnace of a conventional structure. A cross-sectional view of the furnace Matsufuru shown,
Figure 4 is a schematic diagram of the gas exchange chamber provided in the inclined passage at the end of the furnace outlet, Figures 5i and 6 are control circuit diagrams of the exchange chamber shown in Figure 4, and Figure 7 is a diagram of the gas exchange chamber. 8 and 9 are schematic diagrams showing other examples, and FIGS. 10 and 11 are schematic diagrams showing the operating parts of the inlet and outlet shutters shown in FIG.
This figure is a control circuit diagram of the gas replacement chamber shown in FIGS. 7 to 9. DESCRIPTION OF SYMBOLS 1... Article to be processed, 2... Inlet end, 3... Dewaxing section, 4... Sintering section, 5... Cooling section, 6... Outlet end, 7... Conveyor , 8, 9... heating coil, 10.
...Water cooling jacket, 11...Drive roller, 12...
・Guide rollers, 13, 14...Atmospheric gas inlet, 1
5... Atmospheric gas discharge port, 18... Gas curtain outlet, 20... Dewaxing section conveyor, 21... Sintering section conveyor, 22, 23... Drive roller, 24... Upper stage Hearth, 25...Lower hearth, 26...Communication hole, 27
, 2B...Guide roller, 29, 30...Furnace pit, 31...Outside air shielding inclined passage, 32...Normally closed Roshutter, 33...Actuator, 34...Atmospheric gas introduction pipe , 35.36...I) Mitt switch, 37... Shutoff valve, 38... Control circuit, 39,4
0...Shutter, 41...Gas replacement chamber, -4 2
... Waste introduction pipe, 43 ... Gas discharge pipe, 44 ...
Gas introduction pipe, 46...Shutoff valve, 47, 48, 49, 5
0...Limit switch, 51.52...Actuator, 53, 54...Shutter, 55...Gas replacement chamber, 56...Slanted plate, 57...Pivot shaft, 58...
・Spring, 59...Rotating shaft, 60...Bearing, 62...
・Rack, 63... Air cylinder, 64... Atmospheric gas introduction pipe, 65... Discharge pipe, 66... Limit switch, 67, 68, 70, 7σ... Solenoid three-way valve, 7
1...Solenoid valve, 72.73...Timer, 74...
Delay circuit, 75...Delay relay.

Claims (1)

[Scope of Claims] 1. In an atmosphere heating furnace in which a conveyance device is provided in a furnace in which the atmosphere inside the furnace is kept constant, and articles are processed while being moved by this conveyance device, there is a device at the outlet end of the heating furnace. An inclined passage having an inclination angle through which the article slides is provided, and the passage includes a detection means for detecting passage of the article and emitting a signal, an exit shirt stopper that opens and closes based on the signal, and an exit shirt stopper that opens and closes based on the signal. and means for supplying atmospheric gas at least when the furnace is opened. 2. The atmosphere heating furnace according to claim 1, wherein a gas replacement chamber is provided adjacent to the outlet opened and closed by the outlet shutter.