JPH0645839Y2 - Oxidizing atmosphere high temperature furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an oxidizing atmosphere high temperature furnace for performing high-temperature treatment of a heated object such as ceramics.

[Conventional technology]

In an oxidizing atmosphere high-temperature furnace that performs high-temperature processing of heat-treated objects, the processing temperature reaches 1500 ° C or higher, so a heating element is usually installed inside the furnace, and temperature control is performed by observing the coloring of the heating element through the window of the furnace wall. Done. A radiation thermometer is often used to observe the heat generation temperature of the heating element.

[Problems to be solved by the device]

The maximum achievable temperature of the conventional heating element is 1800 ° C. On the other hand, if a zirconia heating element is used as the heating source, it is possible to heat up to a maximum temperature of 2000 ° C in an oxidizing atmosphere.

However, the zirconia heating element is an insulator at room temperature,
Although the electric resistance decreases as the temperature rises, as shown in Fig. 2, it has a practical conductivity of 800 ° C or higher, so it does not function as a heating element from room temperature to several hundreds of degrees Celsius, and the temperature rises. There is a problem that it is not possible to manage the temperature depending on the time. It should be noted that a high temperature of 2000 ° C can be dealt with by using zirconia fiberboard as a fireproof heat insulating material for the furnace wall.

An object of the present invention is to provide an oxidizing atmosphere high temperature furnace that solves the above problems.

[Means for Solving the Problems]

In order to achieve the above object, in an oxidizing atmosphere high temperature furnace of the present invention, a zirconia heating element that is permanently installed in the furnace body, a preheating heating element that can be inserted into and taken out of the furnace body, and the preheating heating element inside the furnace body. A first temperature sensor that is inserted into and removed from the furnace, a second temperature sensor that detects the temperature inside the furnace due to the heat generation of the zirconia heating element, and a second temperature sensor that detects the temperature measurement limit by the first temperature sensor. And a control mechanism for switching to monitoring the temperature inside the furnace by a temperature sensor.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a hearth 2 is openably and closably provided at the bottom opening of a furnace body 1 using a high temperature refractory heat insulating material such as zirconia fiber board.

The structure of the furnace is not limited, but in the case of the embodiment, the furnace body 1
Is installed in the machine frame 11, and the hearth 2 is held by the lifter 12. Therefore, the lifter 12 is mounted on the hearth 2 at the lowered position, the heated object M is housed in the furnace body 1 at the rising end of the lifter 12, and the lower surface opening of the furnace body 1 is provided at the hearth 2. Covered.

In this plan, a zirconia heating element 5 is permanently provided in the furnace body 1, and a nichrome wire heating element, a kanthal heating element or a silicon carbide heating element capable of heating and raising the temperature to 800 ° C. or less is used as the preheating heating element 3. A thermocouple 4 is installed at the core of the heating element 5, and the preheating heating element 3 containing the thermocouple 4 is removably inserted into the furnace body 1 through a small hole 13 opened at the bottom of the furnace body 1. . In addition, the zirconia heating element 5 is hung vertically between the ceiling and the bottom of the furnace body 1 near the furnace wall, and a window hole 14 is provided in a part of the furnace wall adjacent to the heating element 5.
A radiation thermometer 6 for observing the zirconia heating element 5 is installed outside the furnace main body 1 toward 14. The thermocouple 4 measures the temperature in the furnace below 80 ° C by the preheating heating element 1
The temperature sensor and radiation thermometer 6 are the second temperature sensor for measuring the furnace temperature of 800 ° C. or higher by the zirconia heating element 5. However, not only the radiation thermometer is used, but a zirconia resistor thermometer may be installed in the furnace.

The thermocouple 4 and the radiation thermometer 6 are connected to a digital program temperature controller 8 via a signal converter 7 which converts different analog signals for each measured temperature into a continuous signal, and the temperature controller 8 In this case, a preheating power regulator 9 and a zirconia heating element power regulator 10, which are switched between the preheating heating element 3 and the zirconia heating element 5 and are energized, are connected. The temperature controller 8 is a control mechanism that performs switching control by monitoring the thermocouple 4 and the radiation thermometer 6 before and after a set temperature (about 800 ° C.) according to a predetermined program.

In the embodiment, when the heating of the object to be heated M is started, the preheating heating element 3 is caused to generate heat by the energization from the regulator 9 to raise the temperature in the furnace. The temperature inside the furnace is a preset temperature (about 800
(° C) is reached, the input signal of the signal converter 7 is changed to the thermocouple 4
The signal from the radiation thermometer 6 is switched to the signal from the radiation thermometer 6, and the switching control of the digital program temperature controller 8 switches the power supply from the regulator 10 to heat the zirconia heating element 5. At the same time, the preheating heating element 3 is pulled out from the furnace. The withdrawal of the preheating heating element 3 may be artificially performed after the energization of the zirconia heating element 5 is switched, but it can be automatically performed using a switching command of the controller 8.

After that, the object to be heated M is heated by the heat generated by the zirconia heating element 5, and heating up to the maximum temperature of 2000 ° C. is possible. After the heat treatment of the object to be heated M, when temperature control is required at the time of temperature decrease, the preheating heating element 3 is inserted into the furnace when the temperature becomes equal to or lower than the set value, and the heating is performed by energization.

[Effect of device]

As described above, according to the present invention, by using the preheating heating element and the zirconia heating element in a switching manner, it becomes possible to accurately control the temperature in the furnace during the temperature rise and the temperature decrease.
Further, by using the zirconia heating element, it is possible to realize a high temperature furnace in an oxidizing atmosphere which reaches a maximum temperature of 2000 ° C. by utilizing its characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention, and FIG. 2 is a view showing heat generation temperature characteristics of a zirconia heating element. 1 ... Furnace main body, 2 ... Hearth floor 3 ... Preheating heating element, 4 ... Thermocouple, 5 ... Zirconia heating element, 6 ... Radiation thermometer, 7 ... Signal converter, 8 ... Digital program temperature control Total 9 …… Power regulator for preheating 10 …… Power regulator for zirconia heating element 13 …… Small hole, 14 …… Window hole

Claims (1)

[Scope of utility model registration request] 1. A zirconia heating element that is permanently installed in a furnace body, a preheating heating element that is inserted into and removed from the furnace body, and a first temperature sensor that is inserted into and removed from the furnace body together with the preheating heating element. And a second temperature sensor that detects the temperature inside the furnace due to the heat generated by the zirconia heating element, and control that detects the temperature measurement limit by the first temperature sensor and switches to monitoring the temperature inside the furnace by the second temperature sensor. And a high temperature furnace in an oxidizing atmosphere.