JPH0293019A - Heat treatment - Google Patents

Abstract

PURPOSE:To prevent the inside of a heat treating chamber from rising to an abnormal temp. by continuously introducing the external air into the heat treating chamber when the inside of the heat treating chamber attains a prescribed treatment temp., thereby executing the heating control while maintaining the always cooled state in the furnace. CONSTITUTION:An article 4 to be heat treated is carried into the heat treating chamber 2 and an opening/closing door 3 is closed to attain a hermetic state. A circulation fan 10 is driven to allow hot air to flow and circulate in an arrow direction A while a heater 12 is held turned on. A controller 23 emits a signal to open a suction damper 20 and a discharge damper 21 when a temp. sensor 22 detects that the temp. in the heat treating chamber 2 attains the specified treatment temp. The introduction and discharge of the external air are thereafter executed and the on and off control of the heater 12 is executed. The inside of the heat treating chamber 2 is temp.-controlled within the specified accuracy range, by which the long-term heat treatment is effectively executed.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention performs heat treatment by circulating and supplying hot air into a closed heat treatment container such as a heat treatment furnace and heating and maintaining the object to be treated at a predetermined treatment temperature. It relates to a heat treatment method.

(Prior art and its problems) In general, objects to be treated such as aircraft parts such as passenger aircraft wings are placed in a closed heat treatment container, and a heater installed in the container is operated to blow heated air into the container. A heat treatment method in which an object is circulated in a container to raise the temperature to a preset treatment temperature and the object to be treated is maintained at the treatment temperature for a certain period of time is conventionally known.

In such a heat treatment method, maintaining the treatment temperature includes:
This is done by on/off control of the heater based on the detected temperature inside the furnace.

However, it is extremely difficult to maintain the inside of the heat treatment container at a predetermined temperature for a certain period of time only by controlling the heater on and off, and the temperature inside the container fluctuates, which adversely affects the quality of the processed materials. There was a problem of giving.

That is, conventionally, when the inside of the heat treatment container reaches a predetermined processing temperature, the heater is turned off based on the detected temperature inside the furnace and temperature increase is stopped, and the inside of the heat treatment container reaches the predetermined temperature. When the temperature in the heat treatment container reaches a predetermined processing temperature, the heater is turned on again and the temperature is raised to a predetermined processing temperature. Even though the operation of the heat treatment container has been stopped, the temperature inside the heat treatment container is affected by the Joule heat generated by the operation of the circulation fan installed inside the heat treatment container and the accumulated heat accumulated on the inner wall of the container. This has the disadvantage that the temperature rises abnormally rapidly, and this has become a serious problem that must be solved especially when heat treating aircraft parts that require high quality. In particular, when the processing temperature condition is set at a relatively low temperature of 50 to 80°C, the Joule heat and accumulated heat naturally generated within the heat treatment container have a large influence, making it difficult to maintain the temperature inside the heat treatment container at a constant level. It was extremely difficult to do so.

In order to solve these problems, a heat treatment method has been proposed in which the temperature is controlled by using an auxiliary cooler that can offset the amount of heat such as Joule heat and accumulated heat naturally generated in the heat treatment container ( Utility Model Publication No. 62-13535)
.

However, in the above method, it is necessary to provide an auxiliary cooler completely separate from the cooler provided for cooling the inside of the container after the heat treatment is completed, and disadvantages in terms of cost cannot be avoided.

Furthermore, since the amount of heat such as the Joule heat and accumulated heat described above is not constant, there is also the problem that the capacity of the auxiliary cooler cannot be uniquely determined.

(Means for solving the problem) The present invention continuously introduces outside air when the temperature in the heat treatment chamber reaches a predetermined treatment temperature, and performs heating control while keeping the inside of the furnace in a constant cooling state. This prevents abnormal temperature increases in the processing chamber due to Joule heat, accumulated heat, etc., without using a special auxiliary cooler.

That is, according to the present invention, hot air is circulated and supplied into the closed processing chamber, and the object to be processed is heated to a predetermined processing temperature for a certain period of time to achieve thermal IA.
In the burying method, when the temperature in the sealed processing chamber reaches a predetermined processing temperature, the temperature in the sealed processing chamber is raised by continuously introducing and exhausting outside air and controlling the temperature by heating the ambient air inside the processing chamber. A heat treatment method is provided that is characterized by maintaining the treatment temperature at a constant temperature.

(Example) The method of the present invention will be described in detail below based on the accompanying drawings.

In FIG. 1 showing a closed heat treatment apparatus for suitably carrying out the method of the present invention, this heat treatment apparatus (represented as a whole by 1) consists of a heat treatment chamber 2, and the treatment chamber 2 has an opening/closing door 3. The article 4 to be heat-treated is carried in through this door 3, and the article 4 is carried out after the heat treatment.

A heat insulating layer 5 is formed by disposing a heat insulating material on the inner walls of the heat treatment chamber 2 and the opening/closing ff1I3.

Further, the heat treatment chamber 2 is provided with a circulation fan 10, an air flow passage 11 is formed along the inner wall thereof, and a heating heater 12 is further provided within the air flow passage 11.

That is, in this heat treatment apparatus, hot air circulates within the heat treatment chamber 2 as shown by the arrow A, so that the articles 4 carried into the heat treatment chamber 2 are uniformly heat treated.

Furthermore, the heat treatment chamber 2 is provided with an intake damper 20 and an exhaust damper 21, and is also provided with a temperature sensor 22 such as a thermocouple.

In addition, the heating heater 12, the intake and exhaust damper 2
0.21 and temperature sensor 22 are connected to a control device 23, and these are controlled as described below.

In the method of the present invention, the article 4 to be heat treated is carried into the heat treatment chamber 2, the opening/closing door 3 is closed to make it airtight, the circulation fan 10 is driven, and the heating heater 12 is turned on, while hot air is delivered to the heat treatment chamber 2. circulate within. During this time, both the intake damper 20 and the exhaust damper 21 are in the closed state.

According to the present invention, when the temperature sensor 22 detects that the temperature inside the heat treatment chamber 2 has reached a certain treatment temperature, the intake damper 2
0 and the exhaust damper 21 are opened, and from then on, outside air is continuously introduced and exhausted, and the heating heater 12 is controlled ON-OFF II.

That is, in the present invention, after the temperature inside the heat treatment chamber 2 reaches a certain heat treatment temperature, outside air is always introduced, and the amount of cooling is compensated for by ON-OFF control of the heating heater 12, so that the heat treatment can be carried out at a constant temperature. Temperature is maintained.

In this case, Joule heat, accumulated heat, etc. in the heat treatment chamber 2 are suppressed by cooling by introducing outside air.

For example, FIG. 2 shows a diagram showing the relationship between the temperature in the heat treatment chamber and time when the heat treatment temperature is 100°C.

That is, in the present invention, when the internal temperature of the heat treatment chamber 2 reaches the treatment temperature (100° C.) and outside air is not introduced, the heat treatment chamber 2 is heated for a particularly long time as shown by the broken line in FIG. When the heat treatment is performed, the temperature inside the heat treatment chamber 2 rises due to the action of Joule heat and accumulated heat, and this cannot be avoided only by stopping the heater and dissipating heat from the heat insulation layer 5. .

According to the present invention, after a certain heat treatment temperature is reached, outside air is constantly introduced and discharged, so the amount of heat such as Joule heat and accumulated heat is removed, and the amount of heat shown by the solid line in FIG. 2 is removed. Even when heating is performed for a long time, it is possible to control the heat treatment temperature within a certain precision range.

In the present invention, the temperature at which the introduction and exhaustion of outside air is started does not necessarily have to be strictly controlled; it is only necessary that the temperature in the heat treatment chamber 2 is started when the temperature in the heat treatment chamber 2 reaches a range of ±5°C of the temperature to be heat treated. good.

After the introduction and exhaustion of outside air has started, the heating heater 1
2, the heat treatment chamber 2 is maintained within an extremely strict temperature range, for example within the range of ±1.5°C of the heat treatment temperature.
It is possible to hold the inside.

(Effects of the Invention) According to the present invention, the amount of heat such as Joule heat and accumulated heat can be removed without using a strict cooler such as an auxiliary cooler, which is extremely advantageous in terms of cost.

In addition, since outside air is constantly introduced and exhausted after it reaches the heat treatment chamber, in reality, only ON-OFF control of the heater is performed, and only the drive control of the cooler is performed. No special control means are required.

The method of the present invention is effectively applied to long-term heat treatment in a relatively low temperature range that is highly susceptible to the effects of Joule heat, accumulated heat, and the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a heat treatment apparatus for suitably carrying out the method of the present invention, and FIG. 2 is a diagram showing the relationship between temperature in the heat treatment room and time. 2... Heat treatment chamber 10... Circulation fan 12... Heater 21... Exhaust damper 4... Treated article 11... Airflow passage 20... Intake damper 22... Temperature sensor

Claims (1)

[Claims] (1) In a method of heat treatment by circulating and supplying hot air into a sealed processing chamber and heating the workpiece to a predetermined processing temperature for a certain period of time, when the temperature in the sealed processing chamber reaches the predetermined processing temperature, A heat treatment method characterized by introducing and exhausting outside air, and maintaining the temperature inside a sealed processing chamber at a constant processing temperature while controlling the temperature by heating the atmosphere in the processing chamber.