JPS6343673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to a heating furnace, and more specifically, to a continuous heating furnace suitable for using a light gas such as hydrogen as an atmospheric gas.

2. Prior Art Continuous heating furnaces are generally provided with a temperature increasing zone on the inlet side, a high temperature holding zone in the center, and a cooling zone on the outlet side, and a predetermined temperature curve is provided in the furnace as necessary. Furthermore, the atmosphere inside the furnace is changed to a predetermined atmospheric gas as necessary, so that heat treatment,
It is used in a wide range of fields such as sintering in powder metallurgy and firing ceramics.

Especially in the high-temperature holding zone, the temperature inside the furnace is high, and the furnace walls are generally made of refractories, especially firebricks, but since refractories also conduct heat to a certain extent, the heat inside the furnace escapes to the outside of the furnace. The current situation is that there is considerable energy loss. In particular, when the atmosphere inside the furnace is an atmospheric gas containing hydrogen, hydrogen gas penetrates the refractory and has high thermal conductivity, so it directly heats the outer shell of the furnace and raises its temperature. Heat is dissipated outside the furnace, further increasing energy loss. There is a method of covering the outside of the refractory bricks with insulating bricks, but this method is not sufficient to solve the above problems, and has the additional problem of increasing the outer circumference of the furnace. This causes problems.

3. Object of the Invention The present invention aims to solve the problems of conventional heating furnaces as described above, and to provide a heating furnace with good heat insulation and low energy loss.

4. Structure of the Invention That is, the first invention of the present invention comprises an inner shell made of a heat-resistant metal plate, an outer shell made of a metal plate provided outside the inner shell at a distance from the inner shell, and an inner shell and an outer shell. It has a multi-layer furnace wall structure including a heat insulating material filled in a space formed between the inner shell and a refractory lining layer provided inside the inner shell, and the inner shell on the hearth side. and at least the upper surface of the inner shell of the outer shell is an inclined surface such that the center portion is located at a lower level than both side edges, and there is a space between the inner shell and the lining layer on the hearth side. , the second invention relates to a heating furnace characterized by being provided with a heat-resistant metal support member for supporting this lining layer, for example, the crosspiece 22 in the embodiments described below, and the second invention is the same as the first invention. The present invention relates to a heating furnace characterized in that a space between an inner and outer shell of the heating furnace is connected to a pressure reducing device that reduces pressure in this space.

5 Examples Example 1 First, the details of the first invention will be explained with reference to the attached drawings.

FIG. 1 is a plan view showing an example of a continuous heating furnace for firing IC substrates, and FIG. 2 is a sectional view taken along the line - in FIG. 1. A green (to-be-fired) substrate (not shown) is placed on a refractory tray 31 (not shown in FIG. 1) and is moved by the main pusher 13 in the direction of the arrow in the figure. They are fed into the furnace main body 3 one after another from the first charging chamber 1, pass through a temperature rising zone 3a, a high temperature holding zone 3b, and a cooling zone 3c, and are then heated and held at a high temperature in the furnace according to the temperature curve shown in Fig. 3. The pellets are baked through a cooling process and sent to the first outlet chamber 4, then passed through the second outlet chamber 5 and the first table 6 extending to the second outlet chamber 5, and then the first pallet 8. A conveyor 9 moves upward and is provided parallel to the furnace body 3 above the first guide 7 by a drive device (not shown).
It is sent to a position in contact with the end of the furnace outlet side.

The charge is heated by an electric resistance heating element (not shown) connected to a terminal 3d, the temperature is measured by a thermocouple 3e inserted into the furnace from the ceiling, and the temperature is measured by a control device (not shown). A predetermined temperature curve is maintained.

The trays on the conveyor 9 are sent one after another from the furnace outlet side end to the furnace inlet side end by the tray return pusher 14, and are moved onto the second pallet 11.
Next, a second table 12 is extended over the second guide 10 into the second charging chamber 2 by a drive device (not shown), and then the second table 12 is extended through the second charging chamber 2 to the first charging chamber 1. It is beginning to be sent to

The movement of the trays from the second pallet 11 to the second charging chamber 2 via the second table 12 is carried out by the first subsidiary pusher 15. The movement from the second outlet chamber 5 to the The movement through the first table 6 to the first pallet 7 is effected by a fourth sub-pusher 18.

In the furnace body 3, 60 trays 31 are lined up in one row, and the trays 31 are passed through the furnace body 3 over a period of 8 hours. Further, while the tray is moving on the conveyor 9, the fired substrate is collected from the tray, and a green substrate is placed thereon.

The atmospheric gas in the furnace body 3 is relative to the nitrogen gas 3.
AX gas (ammonia decomposition gas) is a mixed gas mixed at a ratio of 5, and the gas is supplied into the furnace through the cooling zone 3c, the first charging chamber 1 and the first outlet chamber 4.
This is done through the gas introduction hole 3f provided in the ceiling of the building. 3g is an explosion-proof valve.

Most of the atmospheric gas introduced into the furnace body 3 passes through the door 1 between the first charging chamber 1 and the second charging chamber 2.
The gas is sent to the second charging chamber 2 through the gas passage hole 1b provided in a. When the door 2a that opens and closes between the second charging chamber 2 and the outside is opened, the gas released from the second charging chamber 2 to the outside is ignited and becomes a flame.
A frame curtain is formed at the boundary between the second charging chamber 2 and the outside to prevent outside air from entering.

The remaining part of the atmospheric gas is sent to the second outlet chamber 5 through a gas passage hole 4b provided in the door 4a between the first outlet chamber 4 and the second outlet chamber 5. When the door 5a that opens and closes between the second outlet chamber 5 and the outside is opened, the gas released from the second outlet chamber 5 to the outside is ignited and becomes a flame, which separates the second outlet chamber 5 from the outside. A frame curtain is formed at the border to prevent outside air from entering.

As shown in Figure 4, which is a sectional view of the second charging chamber and its surroundings taken along the - line in Figure 1, the atmospheric gas is located at the back of the second charging chamber 2 in the figure. After passing through a first charging chamber (not shown), the first door 1a is opened.
It enters the second charging chamber 2 through the first gas passage hole 1b provided in the floor, and passes through the gas discharge hole 2b provided in the floor to the gas discharge pipe 2c and the control valve 2d provided in the middle thereof. is ignited and discharged. The amount of atmospheric gas supplied into the furnace is adjusted by the control valve 2d.

When the second door 2a is opened, the ignition pipe 33 is provided near the lower end of the second door 2a in the closed state in a direction perpendicular to the moving direction of the charge, and is connected to an ignition pipe 33 having a large number of nozzles 33a. The fuel gas released from the nozzle of the ignition pipe 33 is ignited by the pilot burner 32, and the atmospheric gas is released from the second charging chamber to the outside. is ignited, becomes a flame, and enters the second charging chamber 2.
A frame curtain is formed at the boundary between the air and the outside to prevent outside air from entering, and the air is exhausted through the hood 34.

The transfer of the charge from the second pallet 11 to the second charging chamber 2 is carried out by the first subsidiary pusher 15 (see Fig. 1) with the second door 2a open.
Transfer of the charge from the second charging chamber 2 to the first charging chamber 1 is carried out by the second secondary pusher 16 (see Fig. 1) with the first door 1a open. However, at least one of the second door 2a and the first door 1a is always closed.

The second outlet chamber 5 and its surroundings also have the same mechanism as the second charging chamber 2 and its surroundings.

As shown in FIG. 5, which is a cross-sectional view taken along line V-V in FIG.
It has a double structure with an inner shell 19 and an outer shell 20 made of a carbon steel plate SS41 with a thickness of 9 mm provided apart from each other, and the space between the two is filled with ceramic fiber 21 as a heat insulating material. There is. 19a is inner shell 1
This is the reinforcing rib attached to 9.

In this example, the maximum temperature inside the furnace is 1600°C in the high temperature holding zone 3b, and the temperature of the inner shell 19 rises to several hundred degrees, so SUS310 is used as the material for the inner shell 19. In general, it is preferable to use an appropriate material depending on the temperature inside the furnace.

Furthermore, the inside of the inner shell 19 is lined with refractory bricks 23. By making the side wall of the furnace have a multilayer structure in this way, even if the inner shell 19 is heated by the heated atmospheric gas and the refractory bricks 23, the outer wall 20
Heating is small, and the ceramic fibers 21 filled between the inner and outer walls 19, 20 further increase the insulation effect and prevent the heat inside the furnace from being released outside the furnace. As mentioned above, this effect
Since hydrogen gas easily penetrates the refractory bricks and directly heats the outer shell of the furnace, it is particularly large when the inside of the furnace is made into a hydrogen atmosphere or an atmosphere containing hydrogen.

In the case of a continuous heating furnace where the temperature varies depending on the position in the furnace, the outer shell of the furnace is distorted during operation, causing unevenness on the hearth surface. It may be difficult to transport the substrate (substrates placed on it). Therefore, as shown in Fig. 5, the floor of the furnace shell is made into an inclined surface so that the central part is located at a lower level than both ends, and a heat-resistant steel crosspiece 22 is placed on top of the slope. The inner refractory bricks 23 are laid flat so that the inner refractory bricks 23 are supported by the crosspieces 22. With such a hearth structure, even if strain occurs in the hearth during operation, the strain is absorbed by the floor of the hearth, which means that the hearth bulges only outward. Therefore, the refractory bricks in the hearth can maintain a flat surface, and there is no difficulty in transporting the charge inside the furnace. In this example, a crosspiece 22 made of a heat-resistant steel plate SUS310S and having a thickness of 6 mm and a width of 40 mm as shown in FIG. 6 is used in the high temperature holding part of the furnace body.

By having the above structure, the furnace body 3
In a continuous heating furnace with a total length of 9500 mm, a high temperature holding zone 3b length of 3500 mm, and internal dimensions of a width of 315 mm and a height of 250 mm, under the above operating conditions, an outer shell made of a conventional single steel plate was heated. In the case of a structure, the energy released into the atmosphere in the high temperature retention zone is 1800Kcal/m ²・hr
However, by making the furnace wall structure a double structure of an inner shell and an outer shell, this has been reduced to 1500Kcal/m ² .
hr, and by using the structure of the present invention in which the space between the inner and outer shells is filled with ceramic fibers, this was further reduced by half to 900 Kcal/m ² ·hr compared to the case of the conventional outer shell structure.

Example 2 Next, the second invention of the present invention will be explained.

The second invention further reduces energy loss by reducing the pressure in the space between the inner and outer shells of the first invention to prevent heat from propagating from the inside of the furnace to the outside of the furnace due to air convection or conduction. This is what we are trying to achieve.

As shown in FIG. 7, which shows a cross section of the high-temperature holding zone, the furnace wall is made of an inner shell 24 made of heat-resistant steel plate SUS310S with a thickness of 6 mm and a carbon steel plate with a thickness of 9 mm. It has a double structure with an outer shell 25 made of steel plate SS41, the space between them is filled with ceramic fiber 26, and an inner shell 24.
The inside is lined with firebrick 28. Further, as in the first embodiment, the hearth has a floor part of the outer shell that is inclined so that the central part in the direction perpendicular to the axis of the furnace is located at a lower level than both sides. 6
Heat-resistant steel plate with a thickness of 6 mm and a width of 40 mm as shown in the diagram
The crosspieces 22 made of SUS310S are lined up, and refractory bricks 28 are laid on top of them.
It is supported by 24a is a reinforcing rib attached to the inner shell 24, and a hole 24b passes through it so as not to block the space on both sides of the rib.

In addition to the first aspect of the invention, the outer shell 25 is provided with an exhaust hole 25a, which communicates with a conventional pressure reducing pump 30 via a pipe 29, so that the space between the inner and outer shells is depressurized. be. By using this structure and reducing the pressure in the space to 10 ^-1 Torr, the energy in the high temperature holding zone can be released into the atmosphere under the same conditions as in Example 1.
460Kcal/ ^m2 ． hr could be further reduced by about half compared to that of the first invention in Example 1 (900 Kcal/m ² ·hr).

6 Effects of the invention As explained above, when using the heating furnace according to the first invention, the heat insulation effect is significantly increased compared to when using the conventional heating furnace, and when using the heating furnace according to the second invention, Compared to the heating furnace according to the first invention, the heat insulation effect is greater and energy loss is significantly reduced, and both have great industrial utility value from the viewpoint of energy conservation. Furthermore, the structure of the hearth part,
At least the upper surface of the inner shell is a sloped surface such that the center portion is located at a lower level than both side edges, and a heat-resistant metal support is provided between the sloped surface and the refractory lining layer to support the lining layer. Due to the structure in which the members are interposed, even if the furnace shell is strained during operation, this strain is absorbed by the inclined surface and the surface of the lining layer is not deformed. As a result, there is no difficulty in transporting the objects to be heated within the furnace, and operations can be carried out smoothly over a long period of time.

[Brief explanation of the drawing]

1 to 6 are drawings for explaining an embodiment of the first invention, and FIG. 1 is a plan view of a continuous heating furnace;
Figure 2 is a sectional view taken along the line - in Figure 1, Figure 3 is a graph showing the temperature curve inside the furnace, Figure 4 is a sectional view taken along the line - in Figure 1, and Figure 5 is the 1 is a sectional view taken along line VV in FIG. 1, and FIG. 6 is a plan view showing the shape of the crosspiece. FIG. 7 is a cross-sectional view of a high-temperature holding zone in an embodiment of the second invention. Regarding the symbols used in the drawings, 3.
...Furnace body, 3a...Temperature rising zone, 3b...High temperature holding zone, 3c
...Temperature zone, 19,24...Inner shell, 20,25...Outer shell, 21,26...Insulating material (ceramic fiber),
22... Crosspiece, 23, 28... Refractory lining (firebrick), 25a... Exhaust hole, 29... Pipe, 30... Decompression pump, 31... Tray.

Claims (1)

[Scope of Claims] 1. An inner shell made of a heat-resistant metal plate, an outer shell made of a metal plate provided on the outside of the inner shell at a distance from the inner shell, and formed between the inner shell and the outer shell. It has a multilayer furnace wall structure comprising a heat insulating material filled in a space filled with heat, and a refractory lining layer provided inside the inner shell, and the inner shell and the outer shell on the hearth side. At least the upper surface of the inner shell is an inclined surface such that the center portion is located at a lower level than both side edges, and this lining layer is provided between the inner shell and the lining layer on the hearth side. A heating furnace characterized by being provided with a heat-resistant metal support member for supporting the heating furnace. 2. An inner shell made of a heat-resistant metal plate, an outer shell made of a metal plate provided outside the inner shell at a distance from the inner shell, and a space formed between the inner shell and the outer shell filled with It has a multi-layer furnace wall structure comprising a heat insulating material and a refractory lining layer provided inside the inner shell, and at least the inner shell of the inner shell and the outer shell on the hearth side. The upper surface is an inclined surface such that the center portion is located at a lower level than both side edges, and a heat-resistant layer is provided between the inner shell on the hearth side and the lining layer to support the lining layer. A heating furnace characterized in that a metal support member is provided, and a space between the inner shell and the outer shell communicates with a pressure reducing device that reduces the pressure in this space.