JPH03260591A - Continuous sintering furnace - Google Patents

Abstract

PURPOSE:To easily clean a contaminated furnace wall by using a heat-resistant stainless metal plate as the furnace wall material constituting the innermost surface of a degreasing zone and using an alumina refractory material as the furnace wall material of sintering and cooling zones. CONSTITUTION:A degreasing zone 2, a sintering zone 3 and a cooling zone 4 are successively formed to a tunnel-shaped continuous sintering furnace 1 from the inlet 1a thereof toward the outlet 1b thereof. A corrosion- and heat- resistant stainless alloy plate 7 is provided to the degreasing zone 2 as the furnace wall material constituting the innermost surface thereof and an alumina refractory material 8 for heat insulation and reinforcement is provided to the outside of the alloy plate 7. The thermally decomposed matter of a volatilized binder adheres to a furnace wall but, since the furnace wall of the degreasing zone is formed from the corrosion- and heat-resistant stainless alloy plate 7, the adhered flows downwardly along the wall surface of the degreasing zone to prevent the wall surface from the penetration of the adhered or swelling.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a continuous sintering furnace for continuously degreasing and sintering a green body formed from a mixture of sinterable ceramic powder and an organic binder.

[Conventional technology]

In order to produce molded products of ceramic and sintered bodies, a mixture mainly consisting of sinterable ceramic class powder and an organic substance is prepared using a powder pressing method, a doctor blade method, an extrusion method, an injection molding method,
Ceramic green bodies of various shapes are made by slip casting, etc., and then sintered in a patch-type or continuous-type sintering furnace.

When using a batch-type sintering furnace, if the amount of material to be sintered increases, it will require manpower to carry it into and out of the furnace, resulting in poor efficiency.
To produce large quantities of sintered bodies such as industrial parts such as electronic parts and automobile parts, a continuous sintering furnace whose inner wall is made of alumina refractory is used to efficiently degrease and sinter the furnace. .

When sintering in a continuous sintering furnace, a ceramic green body formed by various methods is sintered into a plate-shaped body made of alumina or silica.

Place them on top of each other and store them in their respective bowls.

These pots are stacked in multiple stages, and the stack is pushed by a pusher at the entrance of the furnace, fed into the furnace one by one, and moved on the rails laid in the continuous sintering furnace, and is moved to the degreasing zone, In the sintering zone, a method is used in which the materials are heated and sintered at respective temperatures and then cooled in a cooling zone.

[Problem to be solved by the invention]

However, styrene-based, acrylic-based, wax-based,
When a ceramic green body is formed by mixing a thermoplastic organic substance such as a propylene oligomer with ceramic powder as a binder and is degreased and sintered using a continuous sintering furnace, the organic substance used as a binder is contained in the green body. Since a large amount of table material is used, a large amount of organic decomposition products adheres to the furnace walls in the degreasing zone. There was a problem in that this deposit melted and dripped from the furnace wall soil, etc., and decomposition products accumulated in the exhaust hole of the degreasing zone and leaked out from the joints and the like.

In addition, organic decomposition products that adhere to the surface of the alumina refractory material used as furnace wall materials are tar-like substances that are difficult to remove even during regular cleaning, and furthermore, if they drip onto the rails, This has the disadvantage that stacked pots that move on rails cannot be moved smoothly.

The present invention has been made in view of the above circumstances, and when the ceramic green body is degreased and sintered in a continuous sintering furnace, cleaning of the furnace wall contaminated by organic substance decomposition products generated from the ceramic green body is carried out. To provide a continuous sintering furnace which is large in capacity and does not cause decomposition products of organic substances to drip onto rails and prevent smooth movement of stacked pots.

[Means to solve the problem]

In the continuous sintering furnace of the present invention, a stainless steel heat-resistant metal plate is used as the furnace wall material constituting the innermost surface of the degreasing zone, and a refractory material made of alumina is used as the furnace wall material of the sintering zone and the cooling zone. This was the solution.

〔Example〕

FIG. 1 is a longitudinal sectional view showing an embodiment of a tunnel-shaped continuous sintering furnace l according to the present invention, in which a degreasing zone 2, a sintering zone 3, and a cooling zone 4 are arranged from the inlet 1a toward the outlet 1b. Formed sequentially.

Inside the continuous sintering furnace 1, rails 6 are laid from the inlet 1a to the outlet 1b, which accommodate ceramic green bodies and move pots (not shown) stacked in multiple stages by pushing them one by one with a pusher 5.

The degreasing zone 2, as shown in the cross-sectional view in FIG.
Corrosion-resistant stainless steel is used as the furnace wall material that makes up the innermost surface.
A heat-resistant alloy plate 7 is attached, and an alumina refractory material 8 is provided on the outside of the alloy plate 7 for heat insulation and reinforcement.

The alloy plate 7 is formed in an arch shape with a slightly pointed tip to prevent attached organic decomposition products from dripping and to allow the decomposition products to flow down along the sides.

Further, ventilation holes 9 are provided on both outer sides of the alloy plate for blowing high-temperature air from the sintering zone 3 to maintain the temperature inside the furnace. The ventilation holes 9 can also be formed in the upper and lower parts of the degreasing zone 2, but in this case, measures against dripping of organic decomposition products are required.

An electric heater 10 for internal heating is provided on the outer side of the alloy plate.
is provided. It is also possible to heat the inside of the furnace by attaching a burner to the ventilation hole 9 instead of the electric heater 10.

As shown in the cross-sectional view of FIG. 3, the sintering zone 3 has a furnace wall made of an alumina refractory material 8, as in the conventional furnace. Also, to heat the inside, use an electric heater lO
' and/or burner 1 installed in the ventilation hole 9'
1 is used.

As shown in FIG. 4, the cooling zone 4 uses an alumina refractory material as the material constituting the inner surface, as in the conventional cooling zone. Further, ventilation holes 9' may be provided to recover waste heat and use it as an auxiliary heat source for the degreasing zone 2.

Furthermore, the ceramics used have a melting point or decomposition temperature of 800°C or higher, preferably 1400°C or higher, and particularly preferably 1400°C or higher.A melting point, decomposition temperature, or sublimation temperature of 800°C or higher is preferable. If it is less than C, deformation or blistering occurs during degreasing.

Examples of ceramics used include alumina,
Examples include silica, silicon carbide, silicon nitride, zirconia, cordierite, and aluminum nitride. Furthermore, a small amount of boron, beryllium, carbon, yttrium oxide, cerium oxide, magnesium oxide, lithium oxide, etc. may be added as a sintering aid. The amount of this sintering aid added is
Usually, the amount is 20 parts by weight or less per 100 parts by weight of the ceramic.

The particle size of the above ceramics has an average particle size of 0. 1-20
A thickness of 0 μm is used, but a thickness of 0.1 to 150 μm is preferred, and a thickness of 0.1 to 100 μm is particularly preferred. If the average particle size is less than 0.1 μm, uniform dispersion is difficult during kneading, and if it exceeds 200 μm, shape retention during sintering will be poor and the density after sintering will be low, making it difficult to use the machine. target strength decreases.

In addition, binders include ethylene polymers, styrene polymers, propylene polymers, ethylene-vinyl acetate copolymers, and copolymers whose main component is alkyl (carbon number 6 or less) methacrylate (50wt% or more). For example, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate), copolymers containing alkyl (carbon number 6 or less) acrylate as a main component (5 Qw t% or more) (for example, polymethyl acrylate,
polyethyl acrylate, polybutyl acrylate). However, "system polymer" refers to a homopolymer of the monomer, and a monopolymer containing the monomer as the main component (at least 50 wt.
%) and means a copolymer with other monomers. A number-average device for these synthetic resin binders [vapor pressure osmomet method]
er)] is usually 2,000-500,000, preferably 4,000-500,000.

In order to mold a green body using the above ceramics and binder, ceramic powder and binder are mixed in a predetermined ratio (usually 5 to 40 parts by weight of binder to 100 parts by weight of ceramic powder), and a powder pressing method is used. A ceramic green body is molded by a doctor blade method, or an injection molding method after forming into pellets.

In order to sinter these ceramic green bodies in the continuous sintering furnace 1, a large number of green bodies are placed in a mortar, further stacked in multiple stages, and then placed one by one into the continuous sintering furnace from the entrance using a busher 5. The degreasing zone 2, sintering zone 3,
It is made to pass through the cooling zone 4.

At this time, the temperature of the degreasing sheath 72 is preferably 300-600'C, particularly 300-500'C. If the temperature exceeds 600°C, the alloy plate will deteriorate, and if the temperature is less than 300'C, the amount of residual binder in the degreased body will increase, causing blisters and cracks in the sintering zone.

The temperature of the sintering zone 3 varies depending on the type of ceramic used, and is in the range of 700 to 1800°C.

In addition, the length of the continuous sintering furnace is 10 to 30 m, and the ratio of the lengths of the degreasing zone, sintering zone, and cooling zone is 70:2.
The range is from 0:10 to 50:25:25. In addition, the moving speed of the stacked pots pushed by the butcher is 0.25 to 2 m/hour, especially 0.25 to 1 m/hour.
m/hour is preferred. If the speed exceeds 2 m/hour, harmful deformation, blistering, and cracking will occur in the sintered body. Also, the speed is 0. If the speed is less than 25 m/hour, sintering takes time and economical efficiency is lost.

The binder contained in the green bodies in the mortar moved by the bushier 5 is thermally decomposed and volatilized in the degreasing zone.

The thermal decomposition products of the volatilized binder adhere to the furnace wall, but since the furnace wall in the degreasing zone is made of a stainless steel corrosion-resistant and heat-resistant alloy plate 7, the deposits flow downward along the wall surface. , will not penetrate or swell the wall surface. Furthermore, it is easy to remove deposits from the walls during periodic inspections, and the inside of the furnace can be maintained under constant conditions. The degreased green body is sintered in the sintering zone and cooled in the cooling zone, but the binder is volatilized in the degreasing zone. ,
Conventional alumina refractories are used.

〔Effect of the invention〕

As described above, in the continuous sintering furnace of the present invention, the inner surface of the degreasing zone where almost all the organic binder is volatilized is formed of a corrosion-resistant and heat-resistant alloy plate made of stainless steel. Organic decomposition products are removed by flowing down and cleaning is easy. In addition, although the inner surfaces of the sintering zone and cooling zone are made of alumina refractories, organic decomposition products are volatilized in the degreasing zone, so there is almost no volatilization in the sintering zone and cooling zone. Kimono will not stick to it. Therefore, the inner surface of the continuous sintering furnace is kept almost constant, the temperature of the furnace can be easily adjusted, and decomposed products do not drip onto the rails. Therefore, the moving speed of the mortar moving through the furnace is maintained at a constant speed, and there are many advantages such as ease of quality control without causing unevenness in the product.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the continuous sintering furnace of the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. −■ Cross-sectional view taken along the line, Figure 4 is the ■− of Figure 1.
■It is a sectional view taken along the line. 1... Continuous sintering furnace. 1a... Entrance, l
b...Outlet, 2...Degreasing zone, 3.
... Sintering zone, 4 ... Cooling zone, 5
...Butsusha-6...Rail, 7...
...Alloy plate, 8...Alumina refractory material, 9
・9'・9'・・・Ventilation hole, 10・10'...
...Electric heater, 11...Burner.

Claims (1)

[Claims] In a continuous sintering furnace, a green body formed from a mixture of a binder mainly composed of organic substances and ceramics is passed through a degreasing zone, a sintering zone, and a cooling zone to degrease and sinter it. A continuous sintering furnace characterized in that a stainless steel heat-resistant alloy plate is used as the furnace wall material constituting the furnace wall, and a refractory material made of alumina is used as the furnace wall material in the sintering zone and the cooling zone.