JPS62151508A - Method for controlling slow cooling of batch operated annealing furnace - Google Patents

Abstract

PURPOSE:To eliminate the quick cooling in slow cooling and to obtain an adequate slow cooling rate by once disconnecting an operation signal of a temp. controller from a control system in a slow cooling stage and setting and maintaining a cooling source at a min. control state then resetting the above-mentioned operation signal to the control system. CONSTITUTION:The temp. of a batch operated annealing furnace 10 is detected by a thermocouple 28 and the air for combustion is controlled with a control motor 18 of a damper 20 by a programmed temp. controller 32; at the same time, gaseous fuel is regulated with a pressure equalizing valve 14 to make a soaking operation. The above-mentioned temp. controller 32 is thereafter changed over from the soaking state to the slow cooling state and the cooling source is controlled with a control motor 24 of a damper 26 in the stage of starting the slow cooling operation. The operation signal of the temp. controller 32 is once disconnected from the control system for the prescribed with a timer 34 upon changing over to the above-mentioned slow cooling stage and the control state of the cooling source is set and maintained in the temp. deviation range where the output voltage of the temp. controller 32 is min. The operation signal is reset to the control system after said output value attains the min. value.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to a batch type annealing furnace for slow cooling a+l? Regarding the i1 method, it is particularly suitable for use in small-walled annealing furnaces where the volume of the object to be annealed is large relative to the furnace volume, such as rolling rolls and large-sized vehicles, and where the furnace atmosphere gas temperature easily reacts to disturbances. The program temperature controller that controls the heat source during soaking is set to 01 in the opposite direction during slow cooling, and the slow cooling rate is controlled by controlling 7J] K+. This paper relates to an improvement in a slow cooling control method for a furnace. [Conventional technology l A small batch type annealing furnace is used to roll rolls and large fr!
When annealing objects to be annealed, such as hanging objects, conventionally, as shown in Fig. 4, for example, as shown in Fig. 4, the ambient temperature is uniformly heated at a constant rate to a temperature set according to the purpose of annealing and the composition of the object to be annealed. When the set temperature is reached, the object to be annealed is soaked for a certain period of time so that the internal temperature is uniform. The so-called natural cooling inside the furnace 7J1 method, in which the material is taken out of the furnace, is used. In this furnace natural cooling 71 method, as shown in Fig. 4, the opening degree of the control damper of the heat source, such as the combustion air supply, is controlled by a program temperature controller during the stomach temperature process and the soaking process. During the furnace cooling stage, river control (no stringing is performed)41. In this in-furnace natural cooling method, the cooling rate is extremely fast, and the material to be annealed is heated until it is taken out of the furnace. As the time is longer, there is a problem with workability.In order to solve this problem, the slow cooling rate after soaking can be set, and a program temperature controller can be used to control the cooling source, such as a cooling fan. A method has been proposed in which the opening degree of a damper is controlled to obtain a set slow cooling rate.One such conventional slow cooling control method is shown in Figs. 5 and 6. As shown, the program temperature Tf!J meter that controls the heat source during soaking is switched to the controlled object during slow cooling, and the fiA degree deviation from the set hot water temperature is operated in the opposite direction to control the cooling blower. By this method, slow cooling can be performed at any speed.In other words, in this method, during soaking, the program temperature WJ saving output is set in the direction of reducing the heat source for positive temperature deviations. , operates in the direction of increasing the heat source for negative temperature deviations,
On the other hand, during slow cooling, for positive temperature deviations, the controller operates in the direction of opening the separate control/roll damper for air blowing, causing I have to. In addition, as another method of slow cooling control, as shown in Fig. 7,
A method has also been proposed in which the cooling blower is rotated at the same time as switching from the soaking state to the slow cooling stage, and the control damper is opened step by step with a timer, while the heat source is controlled by a program temperature controller to perform slow cooling. ing. [Problems to be Solved by the Invention] However, when the output of the former program temperature controller is switched from the heat source to the control damper of the cooling feed Elf,
In the conventional slow cooling control method, which uses temperature deviation from the set temperature by reverse operation, etc. ; Suni program 4th adjustment,
-1 output is in a state where the heat source is fully throttled, and from this state it is switched to the slow cooling stage (when moxibustion is performed, the output of the program temperature controller becomes close to the fully open value. As a result, the cooling air blower is controlled by the control damper). is in a fully open state, and the atmosphere inside the furnace is likely to react to external disturbances, especially when annealing a relatively large product relative to the internal volume in a small annealing furnace. Due to the reversal of the temperature controller output, a 2-cooling phenomenon occurs in which the ambient temperature drops to m'fla immediately after switching to the slow cooling stage.This rapid cooling phenomenon decreases by 1 in a short period of time, but after decay However, since the ambient temperature is considerably lower than the set value, the ambient temperature will approach the set value with the control gun closed.As a result, the object to be annealed will be cooled to 7J].
-The air volume required for the annealing becomes insufficient, the temperature gradient of the object to be annealed becomes gentle, and a large temperature difference occurs between the ambient temperature and the object to be annealed. On the other hand, in the latter slow cooling control method, which listens to the control damper in stages using a timer during the slow cooling stage, the interval between the control damper opening IX is The hunting phenomenon cannot be prevented unless the minimum 5% is set to 5 or more steps.As a result, the number of controlled parts increases. [Objective of the Invention] The present invention has been made to eliminate the above-mentioned conventional problems, and is capable of solving the 8-cooling phenomenon at the start of slow cooling. The purpose of the present invention is to provide a slow cooling control method for a batch type annealing furnace that can reduce the temperature difference between 4 degrees and the temperature of the object to be annealed to an appropriate slow cooling rate of 1q. The present invention provides a program temperature [means for controlling] the heat source during scorching heat.
11. A method for controlling slow cooling of a batch type sintering furnace in which the slow cooling rate is controlled by controlling the cooling source by moving the controller in the opposite direction during slow cooling, At the same time as switching from the soaking state to the slow cooling stage, 1) Turn off the F3 program on the FI program, turn off the 11110 system, and turn off the cooling source. , B] Temperature fl at which the output value of the programmable temperature controller is the minimum; i Set and hold within the difference range, and after the output value reaches the minimum value, 1) Return the operation signal θ to the control system again. In this way, the above objective has been achieved. [Effect 1] The present invention can be used for batch baking as described above. '[When controlling the slow cooling of the i-furnace, at the same time as switching from the scorching state to the slow cooling stage,
The operation of the program temperature controller is once disconnected from the control system (and the control state of the cooling source is set and maintained within the temperature range difference range where the output I direct of the program temperature controller is minimized. Therefore, at the start of gradual cooling, the cooling source is not operated at full capacity at the 113 output of the program temperature control Iη regulation, and the 2-cooling phenomenon can be demonstrated.Also, when the output value is the minimum Since the operation signal is later returned to the control system, it is possible to smoothly return to the control of the cold 7.1I source using the 1g 4U controller. [Example] See the drawings below. An embodiment of control equipment for a batch type small-sized annealing furnace in which the slow cooling control method according to the present invention is adopted will be described in detail.In this embodiment, as shown in FIG. A burner 12 is disposed on the furnace wall.The combustion gas supplied to the burner 12 is controlled by a pressure equalizing valve 14.The combustion gas supplied to the burner 12 at 111 degrees The combustion air is generated by a combustion air blower 16, and the combustion air is controlled by a control damper 20 on the Narita side, whose opening degree is controlled by a control motor 18.Thereby, the combustion air is controlled by a control damper 20 on the Narita side. On the other hand, a cooling blower 2 is used to cool the annealing furnace 10.
2 is provided, and the annealing furnace 1 is connected from the cooling vent 22 to the annealing furnace 1.
The flow of cooling air FI"! supplied to the furnace wall is a+lI6n by the control damper 26 whose damping is controlled by the control motor 24. A thermocouple 28 for measuring the ambient temperature is provided.The output of the thermocouple 28 is input to and recorded in a temperature recorder 30, and a program temperature controller for controlling according to the present invention is provided. The program temperature controller 32 inputs the program to the temperature controller 32, which controls the operation output according to the temperature deviation from the set value of the ambient temperature, and adjusts the operation output during temperature rise and uniformity as shown in FIG. 5 above. When the temperature is hot, the control motor 18 is moved in the direction of squeezing the hunt roll damper 20 against the positive temperature deviation.
is feedback-controlled to control the flow of combustion air supplied to the burner 12 so that the temperature during heating and soaking matches the set temperature. On the other hand, when transitioning from the soaking state to the slow cooling stage, the output to the control motor 18 is stopped, the cooling blower 22 is started, and the control motor 24 is controlled via the timer 34.
The control damper 26 outputs an operation signal in the opposite direction to that during temperature rise and soaking so that the set temperature is obtained during slow cooling.
The opening degree of ) to PIt L, the output is stabilized to a value that matches the set temperature, and is prevented by returning to the control system.The temperature at the beginning of this gradual cooling stage, the program temperature controller output, and the cooling blower An example of the relationship between the opening degrees of the control damper is shown in FIG. The control damper 26 is held at a constant 17i1 degree (for example, the minimum opening degree) for several minutes), and the output of the program temperature controller 32 is not disconnected from the control system. , which allows the program to adjust; I32
The output of the pipe decreases to a value corresponding to the temperature deviation. When the program temperature controller 32 is returned to the control system again at point B after a period of time has elapsed, the output stably acts in the direction of making the ambient temperature match the set temperature. As a result, the temperature of the object to be annealed changes in accordance with the set temperature, and good slow cooling control can be achieved. As shown in FIG. 3, if the opening degree of the control damper 26 from the slow cooling start point Δ is too large, the output of the 1-gram temperature controller 32 becomes 0%, and the ambient temperature decreases. Therefore, the time required to reach the set temperature at -V becomes significantly longer. Conversely, if the opening degree of the control damper 26 becomes too small, the time gradient of the output of the programmer t\temperature control unit 32 becomes gentle, and a rapid cooling phenomenon occurs after returning to iQ. Therefore, the maximum jq opening degree is such that a stable state is maintained for several minutes in a range exceeding 0%. In a small batch type annealing furnace using a boudan gas burner as the heat source, when annealing the rolling roll after overlay welding, the slow cooling conditions are set so that the slow cooling rate is 20°C per hour from the soaking section 19600"c. At this time, when switching from soaking to slow cooling, the output of the 1 gram temperature control t132 was 15%, that is, the operating output of the control damper 26 of the cooling blower 22 was From this state, according to the present invention, the output of the program temperature controller 32 was disconnected from the control system, and the opening degree of the cooling blower 22 to the roll damper 26 was maintained at 15% for 30 minutes. Meanwhile, the atmospheric temperature in the furnace was 10°C lower than the set polishing temperature, and at the same time, the output of the program temperature controller 32 became 85% (the operating output of the control damper 26 of the cooling blower 22 was 15%). By restoring the output of the program temperature controller 32 at this point, rapid cooling development did not occur and the slow cooling rate of the object to be annealed could be maintained as set. (Effects of the Invention) As explained above. According to the present invention, it is possible to prevent the rapid cooling of the atmosphere in the furnace at the start of slow cooling.Therefore, the temperature difference between the ambient temperature and the object to be annealed can be compressed to arbitrarily control the slow cooling rate. In particular, when the annealing time is shortened, the present invention has excellent effects such as efficient work.

[Brief explanation of drawings]

FIG. 1 shows the output of the program drum temperature controller at the start of slow cooling and the control damper of the cooling blower in an embodiment of AD control equipment for a batch type annealing furnace in which the slow cooling control method according to the present invention is adopted. A diagram showing an example of the relationship between the opening degree and each temperature,
Fig. 2 is a pipe diagram including a partial block diagram showing the overall groove configuration of the embodiment, and Fig. 3 is the set opening of the control damper of the cooling blower at the starting point of slow cooling in the embodiment. Diagram No. 4121 shows an example of the relationship between the output of the program temperature controller and the output of the program temperature controller. The figure shows an example of the relationship among the operating states of the heat pattern, program temperature controller, heat source, and cooling pressure in an example of the conventional slow cooling A1 control method.
6 is an enlarged diagram showing the section ■ in FIG. 5, and FIG. 7 is a diagram showing the heat pattern, program temperature controller, heat source, and cooling in another example of the conventional slow cooling control method. An example of the relationship between the operating status of the blower claw is shown! It is a #' diagram. 10... Annealing furnace, 12... Burner, 16... Combustion air blower, 18.24... Control motor, 20.2
6... Control damper, 22...
Cold 7. I] Air blower +ii, 28...Thermocouple, 32...Program temperature controller, 34...
...Timer, A...Start point of slow cooling. Agent Takaya Ron, Keisuke Matsuyama Figure 1 Figure 2 Figure 3 Figure 4 Seki Figure 5 Figure 6 Gol! l19L view Figure 7

Claims (1)

[Claims] (1) A batch type annealing furnace in which the slow cooling rate is controlled by operating the programmed temperature controller that controls the heat source during soaking in the opposite direction during slow cooling to control the cooling source. In the slow cooling control method, at the same time as switching from the soaking state to the slow cooling stage, the operation signal of the programmed temperature controller is temporarily disconnected from the control system, and the control state of the cooling source is changed.
A batch type annealing furnace characterized in that the output value of a program temperature controller is set and maintained within a temperature deviation range that minimizes the output value, and after the output value becomes the minimum, the operation signal is returned to the control system again. Slow cooling control method.