JPH0571643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a safety device in a heat treatment furnace such as a vacuum sintering furnace that uses explosive gas.

(b) Prior art For example, in recent years, methods of using explosive gases such as H ₂ , CO, CH ₄ , and C ₃ H ₈ as the atmospheric gas have been proposed and become popular for sintering cemented carbide. It is being done. However, since this sintering work is normally carried out in a vacuum sintering furnace under a suitable reduced pressure condition, if an unexpected leak occurs in the furnace due to a sudden leak or seal deterioration, the above-mentioned Air (oxygen) may be mixed with the explosive gas, causing an explosion. Therefore, in sintering methods that use this type of explosive gas, the biggest technical challenge is to establish safety measures for the vacuum sintering furnace. Furthermore, heat treatment furnaces that use explosive gases other than vacuum sintering furnaces are also required to ensure safety in the same way.

(C) Purpose The present invention has been made in view of this situation, and even if an abnormality occurs in the oxygen ratio of the gas in the furnace due to leakage, etc. in a heat treatment furnace that uses explosive gas, the present invention can be used to immediately It is an object of the present invention to provide a safety device that can sense this and automatically take appropriate safety measures immediately.

(d) Configuration That is, in order to achieve the above object, the present invention includes an oxygen ratio detection means for detecting the oxygen ratio of explosive gas in a heat treatment furnace, and receives oxygen ratio information from the oxygen ratio detection means. In addition, there is a control means configured to output a danger signal when the oxygen ratio of the gas in the furnace reaches the explosion limit ratio set according to the operating conditions or a ratio in the vicinity thereof, and a control means configured to output a danger signal. an oxygen ratio adjustment means for adjusting the oxygen ratio of the gas in the furnace by inputting a signal, and the oxygen ratio adjustment means is connected to a gas supply path that can selectively supply an inert gas into the furnace. and an electromagnetic valve interposed in a discharge path that communicates with the heat treatment furnace and releases the atmospheric gas in the furnace into the atmosphere. .

(e) Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a safety device system according to the present invention, in which a heat treatment furnace, particularly a vacuum sintering furnace 1 in this case, is communicated with a gas supply device (not shown) through a valve 2 in a gas introduction path a. , a gas exhaust path b is connected to a vacuum pump 4 through a valve 3. The vacuum furnace 1 is provided with an O ₂ sensor 5 as one of the oxygen ratio detection means for detecting the oxygen ratio in the explosive gas sealed in the furnace under reduced pressure. The O ₂ sensor 5 transmits oxygen ratio information to the control means 7 via a converter 6 that converts the detection result into an electrical signal.

The control means 7 receives this information, inputs necessary conditions such as the type of gas used and the furnace volume, and sets the explosion limit ratio, which is set according to the operating conditions of the vacuum furnace 1. is stored in its memory. The term "explosive limit ratio" as used herein refers to the upper or lower limit of the stoichiometrically inherent oxygen ratio of various explosive gases at which they can explode. For example, in the case of H ₂ gas, it is possible to explode within the range of 5% to 75% H ₂ (mixing ratio with air), but it cannot explode if there is an excess or deficiency in the amount of H ₂ gas or oxygen. Therefore, in this case, the ratio calculated from the above ratio as the explosion limit ratio, or a certain set ratio in the vicinity thereof, is stored for the purpose of further increasing safety. Note that since it is normally not expected that the oxygen amount exceeds the upper limit ratio, only the lower limit ratio is sufficient, but the upper limit ratio may be stored if necessary. Then, the control means 7 compares and calculates the oxygen ratio information and the explosion limit ratio in its calculation section, and determines whether the oxygen ratio of the in-furnace explosive gas transmitted by the oxygen ratio information is at or near the lower explosion limit ratio. When the oxygen ratio rises to the oxygen ratio, the output section outputs a danger signal O to the oxygen ratio adjustment means described below.

The oxygen ratio adjusting means includes a gas reservoir 8 which is connected to the vacuum furnace 1 by interposing an electromagnetic valve 9 in a gas supply path c that supplies an inert gas into the furnace, and a gas reservoir 8 which is connected to the vacuum furnace 1 by supplying an inert gas into the furnace. It consists of an in-furnace purge mechanism comprised of a solenoid valve 10 interposed in a discharge path d for discharging air. That is, in this in-furnace purge mechanism, when the dangerous O is simultaneously input to the solenoid valve 9 on the supply furnace c side and the solenoid valve 10 on the discharge path d side and both valves 9 and 10 are opened, the supply path c Inert gas such as high-pressure N ₂ and CO ₂ stored in the gas storage device 8 is introduced into the furnace from 1, while the gas in the furnace is discharged to the outside air from the discharge path d, and the gas in the furnace is This instantly lowers the oxygen ratio.

Next, the operation of the safety device having the above configuration will be explained.

The control means 7 receives the oxygen ratio information from the O ₂ sensor 5, and if its calculation part detects an abnormal increase in the oxygen ratio in the furnace gas due to the occurrence of a leak, etc. , the danger signal O will be output from the output part, and appropriate safety measures will be taken immediately. To explain this in detail with reference to Fig. 2, when the vacuum furnace 1 generates a leak etc. in the depressurization control state, the leaked air mixes with the gas in the furnace, and the oxygen ratio rises to the lower limit ratio as indicated by the arrow Oup in the diagram. If the pressure rises to a nearby set pressure, the control means 7 outputs a danger signal O from its output portion to the electromagnetic valves 9, 10 of the parsing mechanism. Then, the valve 9 is opened and inert gas is sent into the furnace from the gas reservoir 8, while
At the same time, the explosive gas in the furnace is released from the discharge path d where the valve 10 is opened, and the oxygen ratio in the gas in the furnace is rapidly reduced as indicated by the arrow Odown in the figure. In other words, in this system, when the oxygen ratio in the explosive gas exceeds a certain level, the inside of the furnace is rapidly replaced with inert gas to eliminate the risk of explosion.

In this way, with this safety device, even if an abnormality such as a leak occurs, the explosive gas in the reactor is kept within a certain oxygen ratio range where it cannot chemically explode, thereby reducing the risk of an explosion accident. Safety can be ensured.

Although sensors and analyzers based on various principles can be applied to the oxygen ratio detection means used in the safety device of the present invention, recent advances in analysis technology have made it possible to detect the oxygen amount (ratio) even under reduced pressure. It can be easily detected. Furthermore, the internal system configuration of the control means 7 is free as long as it has the necessary information processing function and command output device.

Further, in the above embodiment, a case has been described in which an in-furnace purge mechanism is employed as the oxygen ratio adjusting means, but the present invention is not limited to this. For example, vacuum furnace 1
A danger signal is input to the valves 2 and 3 located in the gas introduction path a and the exhaust path b to open the valves, and while explosive gas is supplied from the gas introduction path a, the vacuum pump 4 is used to vacuum the inside of the furnace. It is also possible to lower the pressure and adjust the oxygen ratio in the furnace gas.

In the above explanation, the case of a vacuum heat treatment furnace that uses an explosive gas as the atmospheric gas under reduced pressure has been described as an example, but the safety device of the present invention can also be applied to other atmospheric furnace or pressurized furnace type heat treatment furnaces. The same applies.

(f) Effects As described above, the safety device of the present invention includes an oxygen ratio detection means, a control means, and an oxygen ratio adjustment means in a predetermined combination state, so that the explosive gas in the heat treatment furnace is always kept constant. Since the oxygen ratio is maintained within a non-explosive range, even if air were to get mixed into the heat treatment furnace for some reason, the risk of an explosion would be prevented. Therefore, it becomes possible to implement a wide range of heat treatment methods, including the vacuum sintering furnace described above, as well as heat treatment methods that use explosive gas.

[Brief explanation of drawings]

FIG. 1 is a system explanatory diagram showing an embodiment of the present invention. FIG. 2 is an explanatory diagram showing an example of the operating mode of the embodiment system. 1... Vacuum furnace, 2, 3... Valve, 4... Vacuum pump, 5... O ₂ sensor, 6... Converter, 7...
...Control means, 8...Gas reservoir, 9, 10...Solenoid valve, a...Gas introduction path, b...Gas discharge path, c...Gas supply path, d...Gas discharge path, O...
…Danger signal.

Claims (1)

[Claims] 1 Oxygen ratio detection means for detecting the oxygen ratio of the explosive gas in the heat treatment furnace, receiving oxygen ratio information from this oxygen ratio detection means, and setting the oxygen ratio of the gas in the furnace according to operating conditions. a control means configured to output a danger signal when the explosion limit ratio reached or a ratio in the vicinity thereof; and an oxygen ratio adjustment that adjusts the oxygen ratio of the gas in the furnace by inputting the danger signal from the control means. a gas reservoir connected to a gas supply path capable of selectively supplying an inert gas into the furnace; and a gas reservoir connected to the heat treatment furnace to control the atmosphere in the furnace. A safety device for a heat treatment furnace, characterized in that it is an in-furnace purge mechanism consisting of an electromagnetic valve interposed in a discharge path that discharges gas into the atmosphere.