JPH0627040B2 - Degreasing method for ceramic molded products - Google Patents

Description

TECHNICAL FIELD The present invention relates to a degreasing method for ceramic molded articles.

[Prior Art] Generally, in the manufacturing process of ceramics, molding is performed in a state where fluidity is imparted by adding an organic engaging agent to the ceramic powder. Various molding methods are known in addition to press molding, extrusion molding, and injection molding has the advantage that a ceramic molded product having a complicated shape can be obtained. However,
In order to perform injection molding, the material needs to have high fluidity, and therefore the amount of the organic binder added increases, and a step of degreasing that removes the organic binder that is no longer needed after molding is required.

By the way, in the degreasing process, it is important to set the heating conditions such as the heating temperature, the supply amount of the gas that forms the atmosphere in the furnace, and the amount of oxygen in the gas that forms the atmosphere in the furnace. If so, the ceramic molded product may be cracked or the surface layer may be peeled off.

For example, if the ceramic molded product is excessively heated or the temperature is rapidly raised, the amount of decomposition soot generated by the decomposition of the organic binder per unit time becomes excessive, and inside the ceramic molded product. The gas pressure causes a problem that the ceramic molded product is cracked, swelled, or the surface layer is peeled off.

In order to solve such a problem, conventionally, a temperature sensor such as a thermocouple is used to detect the temperature in the furnace for heating the ceramic molded product, and the temperature in the furnace is set in accordance with a preset heating program corresponding to the temperature in the furnace. The temperature was controlled.

However, the amount of decomposition gas generated by heating the organic binder in the ceramic molded product does not correspond to the temperature one-to-one. Therefore, even if the temperature inside the furnace is controlled based on the temperature inside the furnace, the amount of decomposition gas generated may become excessive.

In order to solve such a problem, a method of detecting the weight of the ceramic molded product instead of the temperature in the furnace and controlling the temperature in the furnace based on the change in weight has been proposed (Japanese Patent Laid-Open No. 61-61). 163172).

[Problems to be Solved by the Invention] However, in order to determine the degreasing state by detecting the weight of the ceramic molded product, the rate of change of the weight of the ceramic molded product must be calculated, and the degreasing work is performed every time. It is necessary to measure the weight of the ceramic molded part. As a result, the load of the control system program for calculating the change rate increases, and the work time of the degreasing process also increases.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a degreasing method for a ceramic molded product in which the determination of the degreased state of the ceramic molded product is simplified in the degreasing step.

[Means for Solving the Problems] In the present invention, in order to achieve the above object, in the degreasing step, a monitor member, which is kept at a temperature equal to or lower than the temperature at which the organic binder is redissolved, is disposed in the furnace. The heating condition in the furnace is controlled based on the change in the state of the monitor member.

[Operation] According to the above configuration, the degreasing state of the ceramic molded product is indirectly determined based on the state change of the monitor member arranged in the furnace without directly detecting the state of the ceramic molded product. The heating conditions in the furnace can be set regardless of the shape, weight, etc. of each individual ceramic molded product, and the condition setting becomes easy.

[Example] A furnace 1 for degreasing a ceramic molded product is equipped with a heater 2 for setting temperature conditions in the furnace 1, as shown in FIG. Air is supplied into the furnace 1 through the valve 3, and an inert gas such as nitrogen is supplied through the valve 4. The openings of these valves 3 and 4 can be continuously adjusted. The gas forming the atmosphere in the furnace 1 is discharged to the outside through the discharge passage 5, and the discharge passage 5 is provided with a safety valve 6. Further, an oxygen concentration detector 8 is arranged in the discharge path 5. The output of the oxygen concentration detector 8 (8a is a sensor portion, 8b is a main body portion) is input to the management computer 9, and based on the concentration of oxygen discharged from the furnace 1, the set temperature of the heater 2 and the valves 3, 4 are set. And the opening degree of are adjusted. The heater 2 is controlled by a thyristor 10 connected to the management computer 9 via an interface, whereby the heating and heating conditions in the furnace 1 are set. Further, the valves 3 and 4 are driven by opening degree adjusters 11 and 12 such as step motors which are connected to the management computer 9 via an interface, respectively, and the air supply amount and the inert gas supply amount into the furnace 1 are controlled. And are adjusted.

By the way, the management computer 9 also uses the state of the monitor member disposed in the furnace 1 as control data. That is, as shown in FIG. 2, a reflecting mirror 25 is provided as a monitor member in the furnace 1, and light from a light source 26 such as a He-Ne laser provided outside the furnace 1 is reflected through a window 27. The mirror 25 is irradiated and the light reflected by the reflecting mirror 25 is observed through the window 28 by the light receiver 29 outside the furnace 1. The reflecting mirror 25 is wrapped in a water cooling jacket and cooled to 50 ° C. This temperature is set to be equal to or lower than the temperature at which the aggregate of the decomposition gas adhering to the reflecting mirror 25 is decomposed again. The light receiver 29 is connected to the management computer 9, and the management computer 9 determines the degreased state of the ceramic molded article 20 according to the amount of light received by the light receiver 29, and supplies the air supply amount and the inert gas supply amount. , Control the temperature.

The control is performed as follows. As shown in FIG.
First, immediately after the start of degreasing, only air is supplied (thick broken line), and the temperature in the furnace 1 rises. At this time, the reflector 2
The reflectance (dashed double-dotted line) of 5 is large, and most of the light from the light source 26 reaches the light receiver 29. When the temperature further rises and the organic binder starts to decompose, the decomposed gas near the surface of the reflecting mirror 25 is cooled and cohesively adheres to the reflecting mirror 25, so that the reflectance is lowered. When the reflectance starts to drop sharply in this way, the management computer 9 adjusts the opening degree of the valve 3 so as to reduce the air supply amount into the furnace 1, and supplies the inert gas (thin broken line). The opening degree of the valve 4 is adjusted so as to increase. Further, the heater 2 is controlled via the thyristor 10 so as to reduce the temperature rise rate in the furnace 1. At this time, the oxygen concentration (dashed line) decreases. Also, the total amount of gas supplied into the furnace 1 is set to increase. When such control is performed, the total amount of gas in the furnace 1 increases,
The atmosphere in the furnace 1 is rapidly updated, the decomposed gas in the surface layer of the ceramic molded product is removed, the escape path of the decomposed gas from the inside of the ceramic molded product is formed, and the swelling of the ceramic molded product occurs. Can be prevented. Further, by rapidly updating the atmosphere, the temperature in the furnace 1 is lowered, the ceramic molded article is cooled, and the decomposition of the organic binder is suppressed. Furthermore, since the amount of inert gas increases and the amount of oxygen decreases, the amount of decomposition gas generated is suppressed. That is, since the increase in gas pressure inside the ceramic molded product is suppressed, it is possible to prevent the ceramic molded product from bulging or cracking. In this way, until the organic binder begins to decompose, it is mainly an atmosphere of only air, the supply amount of the inert gas is increased with the increase in the generation amount of the decomposition gas, and the degreasing progresses sufficiently, It is trying to increase the air supply again. Therefore, the cost in the degreasing process can be reduced as compared with the case where only a relatively expensive inert gas is used.

In the above embodiment, the mixing ratio of air and inert gas is variable, but only the air is supplied into the furnace 1 and the atmosphere is controlled by removing oxygen from the air by a method such as adsorption. Good. Further, in the above embodiment, the reflecting mirror 25 is used as the monitor member and the light reflectance at the reflecting mirror 25 is observed. However, a transparent plate is arranged as the monitor member to observe the light transmittance. You may further,
Instead of light, the reflectance or transmittance of ultrasonic waves or the like may be observed. Alternatively, the degreased state of the ceramic molded product may be indirectly determined by measuring the weight of the monitor member.

EFFECTS OF THE INVENTION As described above, in the present invention, in the degreasing process of a ceramic molded article, a monitor member kept at a temperature equal to or lower than the temperature at which the organic binder is redissolved is disposed in the furnace, and the state of the monitor member is It controls the heating conditions in the furnace based on the changes, and indirectly detects the degreased state of the ceramic molded product based on the change of the state of the monitor member installed in the furnace without directly detecting the state of the ceramic molded product. Therefore, the heating conditions can be set independently of the shape and weight of each ceramic molded product, the load of the control program can be reduced, and the work amount of the degreasing process can be reduced. As a result of degreasing by the above method, it was possible to obtain a ceramic molded product without cracking or swelling.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an embodiment of the present invention, FIG. 2 is a configuration diagram of main parts of the same, and FIG. 3 is an operation explanatory diagram of the same. 1 ... Furnace, 2 ... Heater, 3, 4 ... Bulb, 8 ... Oxygen concentration detector, 9 ... Management computer, 20 ... Ceramic molded product, 25 ... Reflector, 26 ... Light source, Two
7, 28 ... Window, 29 ... Receiver.

Claims (1)

[Claims] 1. In a degreasing process of heating a ceramic molded product composed of ceramic powder and an organic binder in a furnace to remove the organic binder, the temperature is maintained at a temperature equal to or lower than a temperature at which the organic binder is decomposed again in the furnace. A degreasing method for a ceramic molded article, comprising disposing a dripping monitor member and controlling heating conditions in the furnace based on a change in the state of the monitor member.