JP4993237B2 - Magnesium alloy material heating control method and heating furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heating control method and a heating furnace capable of preventing combustion due to ignition in advance when a magnesium alloy or a material made of a magnesium alloy is heated to a predetermined temperature in order to perform forging, press molding, or heat treatment. Is.
[0002]
[Prior art]
When magnesium alloy or magnesium alloy materials (hereinafter collectively referred to as magnesium alloy materials), such as cast materials and rolled materials, are subjected to forging, press forming or heat treatment, these magnesium alloy materials A heating furnace or a heat treatment furnace is charged and heated to a predetermined target temperature, for example, 300 to 450 ° C. In these heating furnaces, a heating means such as a heater and a temperature sensor for detecting the temperature in the heating furnace, such as a thermocouple, are installed in the heating furnace, and based on the temperature detected by this temperature sensor, The control device controls energization of the heater so that the temperature in the heating furnace falls within the target temperature range. However, if the temperature inside the heating furnace greatly exceeds the target temperature range due to some problem, there is a risk of deterioration of the quality of the material to be heated, damage to the heating furnace, fire of the heating furnace, explosion, etc. . In particular, since a magnesium alloy material easily reacts with oxygen at high temperatures, there is a risk of ignition and combustion when the temperature exceeds 500 ° C. In the heating furnace, various safety measures have been proposed in order not to cause the above problems.
[0003]
For example, in Japanese Patent Laid-Open No. 1-287224, in a heat treatment furnace for a metal strip using a burner, a cooling gas (air or atmospheric gas) is blown into the furnace when the furnace temperature exceeds an allowable range. It is disclosed. In Japanese Patent Laid-Open No. 6-147774, in a continuous heating furnace for seamless steel pipes, when the ambient temperature rises to a temperature higher than a preset temperature by a predetermined temperature, the automatic fire extinguishing function is activated to switch to fuel gas. Supplying N ₂ gas. In JP-A-10-79351, a plurality of temperature sensors are installed in a processing furnace such as a CVD apparatus, for the purpose of temperature management capable of discriminating between abnormalities caused by poor control and abnormalities in temperature sensors. It is disclosed that power supply to the heater is stopped when the number of thermocouples exhibiting an abnormality in the detected temperature is large.
[0004]
[Problems to be solved by the invention]
In heating a magnesium alloy material, the magnesium alloy material is a material that easily oxidizes, and if it exceeds 500 ° C., there is a risk of ignition and combustion. Therefore, when heating a magnesium alloy material, if the temperature in the furnace exceeds the target temperature and reaches an abnormal temperature range, safety measures will be taken before the magnesium alloy material ignites and burns. It is important to do. In addition, it is indispensable to adopt a control method that can reliably implement safety measures even when an abnormality occurs in a temperature sensor that detects the temperature in the heating furnace.
The object of the present invention is to burn the magnesium alloy material by ignition when the magnesium alloy material charged into the furnace for heating becomes an abnormal temperature exceeding the target temperature in the furnace. It is in providing the heating control method and heating furnace of the magnesium alloy raw material which can prevent in advance.
[0005]
[Means for Solving the Problems]
The present invention relates to a method for controlling the heating of a magnesium alloy material charged in a heating furnace, and the temperature in the heating furnace is 10 to 20 ° C. higher than a target temperature T0 set in advance for performing forging, press molding or heat treatment. When the abnormal temperature T1 is reached, heating of the heating furnace is stopped, and after the heating is stopped, the temperature in the heating furnace is higher than the abnormal temperature T1 and 20-30 ° C. lower than the ignition temperature of the alloy, and a preset abnormal temperature T2 If it becomes, it is a heating control method of the raw material made from a magnesium alloy characterized by injecting an inert gas in a heating furnace.
[0006]
Further, the present invention is a heating furnace for heating a charged magnesium alloy material, a temperature sensor installed to detect the temperature in the heating furnace, and injecting an inert gas into the heating furnace. When an abnormal temperature T1 that is 10 to 20 ° C. higher than a preset target temperature T0 for performing forging, press molding, or heat treatment is received by receiving the temperature information of an inert gas injection device and a temperature sensor, a heating stop command is issued to the heating means. A control unit having a logic unit that issues a command to inject an inert gas to an inert gas injection device when the temperature reaches a preset abnormal temperature T2 that is higher than the abnormal temperature T1 and lower by 20 to 30 ° C. than the ignition temperature of the alloy And a device.
In the heating furnace, it is desirable to install a plurality of temperature sensors so as to be located 20 to 50 mm away from the magnesium alloy material. Further, a temperature sensor for controlling the heating means may be provided separately from the temperature sensor for monitoring the temperature in the heating furnace. Further, the inert gas injection device may be provided with a fluid pressure driven valve that opens and closes according to a command from the control device in a pipe connecting the container for storing the inert gas and the inside of the heating furnace. Further, the fluid of the fluid pressure driven valve is preferably nitrogen gas supplied from a container for storing nitrogen gas, but is not limited as long as it is supplied so as not to cause a sudden pressure fluctuation, compressed air, argon gas But you can. The inert gas is preferably argon gas, but may be carbon dioxide gas.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view showing an embodiment of a heating furnace of the present invention. In FIG. 1, the heating furnace 1 has a horizontally long furnace body 2, and inside the furnace body 1, a transfer device such as a chain conveyor 3 that proceeds at a predetermined speed is installed. A transfer plate 4 is placed on the chain conveyor 3 at a predetermined interval. A magnesium alloy material 5 to be heated (hereinafter referred to as a workpiece 5) is loaded on the transport plate 4. A heater 6 for heating the inside of the heating furnace 1 to the target temperature T0 is installed at a predetermined interval above the furnace body 2. Further, a plurality of control temperature sensors 7 a and monitoring temperature sensors 7 b for measuring the temperature in the furnace body 2 are installed in the furnace body 2 at predetermined intervals in the longitudinal direction of the furnace body 2. . The control temperature sensor 7a is used to control the inside of the furnace body 2 to the target temperature T0, and the monitoring temperature sensor 7b is used to monitor the temperature inside the furnace body 2. Thermocouples can be used as the plurality of temperature sensors 7a and 7b. Further, these temperature sensors 7 a and 7 b are connected to the control device (control device 10 shown in FIG. 2) of the heating furnace 1, and the detected temperature is input to the control device 10.
[0008]
The plurality of temperature sensors 7 a and 7 b are installed on the upper wall of the furnace body 2, and the temperature detection part has a tip part in the vicinity of the upper part of the work 5, preferably 20 to 50 mm away from the work 5. It is arranged so that the temperature in the immediate vicinity of the workpiece 5 can be detected. At the bottom of the furnace body 2, a plurality of nozzles 8 for injecting an inert gas, preferably argon gas, into the furnace body 2 are installed in the longitudinal direction of the furnace body 2 at a predetermined interval. The nozzle 8 may be a pipe having a small diameter. A cover 9 is provided for uniformly heating the work 5 without directly transferring the heat from the heater 6 to the work 5, and uses a heat-resistant thin plate made of stainless steel or the like. Although not shown in the figure, a loading port is provided in the front part of the horizontally long furnace body 2 and a discharge port is provided in the rear part, and an opening / closing door is provided in each.
[0009]
FIG. 2 shows an example of a control system diagram and a piping route diagram of the heating furnace 1 necessary for carrying out the present invention. In FIG. 2, reference numeral 10 denotes a control device that controls the operation of the heating furnace 1, and is composed of a sequence controller or a microcomputer. The control device 10 controls the energization control of the heater 6 based on the temperature detected by the control temperature sensor 7a, and the opening / closing control of the fluid pressure driven valve 11 based on the temperature detected by the monitoring temperature sensor 7b. , And drive control of the chain conveyor 3, loading / unloading of the furnace body 2, opening / closing of the opening / closing door of the discharge port, and the like. 12 is a solenoid valve, 13 is a container that stores high-pressure argon gas, and 14 is a container that stores high-pressure nitrogen gas that supplies the solenoid valve 12 with nitrogen gas for opening and closing the valve of the fluid pressure driven valve 11. is there. 15a and 15b are pipes for supplying argon gas, and 16 is a pipe for supplying nitrogen gas. The high pressure argon gas storage container 13, the high pressure nitrogen gas storage container 14, the fluid pressure drive valve 11, the electromagnetic valve 12, the nozzle 8, the pipe 14a, and the pipe 14b constitute an inert gas injection device.
[0010]
Then, the heating control method of the heating furnace of this invention is demonstrated. First, the heater 6 is energized in accordance with a control command from the control device 10, and the temperature in the heating furnace 1 is heated to a target temperature T0, for example, in the range of 300 to 450 ° C. when forging. In order to control the inside of the heating furnace 1 to the target temperature T0, the control device 10 controls energization of the heater 6 based on the temperature detected by the control temperature sensor 7a. Subsequently, a predetermined number of workpieces 5 are loaded on the transport plate 4 by a handling robot or the like installed in the previous process of the heating furnace 1. Next, according to a control command from the control device 10, the opening / closing door of the charging furnace 1 is opened, the chain conveyor 3 is driven, and the conveying plate 4 loaded with the work 5 is loaded into the heating furnace 1. The loading operation of the transfer plate 4 loaded with the work 5 is controlled to be performed at predetermined time intervals, and a plurality of transfer plates 4 are loaded in the heating furnace 1. The workpiece 5 charged in the heating furnace 1 is heated for a predetermined time in the heating furnace 1 heated to the target temperature T0, and then discharged together with the transport plate 4 from the discharge port according to a control command of the control device 10, It is conveyed to the next forging or press molding process. In order to prevent oxidation and ignition of the work 5 charged in the heating furnace 1, argon gas is separately supplied into the heating furnace 1 from an argon gas supply device (not shown). An atmosphere with an argon gas concentration of 1 to 5% is preferable.
[0011]
Next, a control method when the temperature in the heating furnace 1 rises from the target temperature T0 and reaches an abnormal temperature due to some trouble when the workpiece 5 is heated in the heating furnace 1 will be described. The control device 10 constantly monitors the temperature in the heating furnace 1 by inputting the temperature values detected by the plurality of monitoring temperature sensors 7b at predetermined time intervals (for example, 0.1 seconds). When the controller 10 detects a preset abnormal temperature T1 (eg, 460 ° C.) in which at least one detected temperature of the plurality of monitoring temperature sensors 7b is higher than the target temperature T0, the controller 10 immediately Stops energization, that is, issues a command to stop heating and activates the alarm device. The value of the abnormal temperature T1 is preferably a temperature that is about 10 to 20 ° C. higher than the target upper limit value of the heating temperature, and the temperature at which the quality of the workpiece 5 does not deteriorate at this T1 temperature. As described above, when the monitoring temperature sensor 7b detects the abnormal temperature T1 that is higher by about 10 to 20 ° C. than the target heating temperature T0, the heating of the heater 6 is stopped, so that the temperature abnormality in the heating furnace 1 is accelerated. Can be detected. Although the abnormal temperature T1 may be erroneously detected due to a malfunction of the monitoring temperature sensor 7b, when at least one monitoring temperature sensor 7b detects the abnormal temperature T1, the heating of the heater 6 is stopped and an alarm is issued. It is safer to operate the device and check for abnormalities in the furnace 1 by a human. Further, since the monitoring temperature sensor 7b detects the abnormal temperature T1, the temperature in the heating furnace 1 does not drop suddenly even when the energization of the heater 6 is stopped. There is no fear of decline.
[0012]
After the control device 10 issues a command to stop energization of all the heaters 6 as described above, at least one of the monitoring temperature sensors 7b has preset the temperature in the heating furnace 1 higher than the abnormal temperature T1. When the abnormal temperature T2 (for example, 480 ° C.) is detected, the control device 10 issues a control command for switching the electromagnetic valve 12 from “open” to “close”. Then, the nitrogen gas that has passed through the electromagnetic valve 12 from the high-pressure nitrogen gas storage container 14 and flows into the drive chamber of the fluid pressure drive valve 11 until now and has closed the valve of the fluid pressure drive valve 11 is shut off. Then, the valve of the fluid pressure driven valve 11 is “open”. When the valve of the fluid pressure driving valve 11 is “open”, argon gas is injected into the heating furnace 1 from the plurality of nozzles 8 through the pipes 15 a and 15 b from the high pressure argon gas storage container 13. By injecting argon gas into the heating furnace 1 in a short time in this way, the inside of the heating furnace 1 is in an oxygen deficient state, and even when the temperature in the heating furnace 1 reaches the abnormal temperature T2, the workpiece 5 Ignition can be prevented. The abnormal temperature T2 is set to a temperature lower than the ignition temperature of the workpiece 5, preferably at least 20 to 30 ° C. lower than the ignition temperature of the workpiece 5. The supply pressure of the argon gas may be about 2 MPa.
[0013]
As described above, the reason for using high-pressure nitrogen gas as a drive source for driving the fluid pressure driven valve 11 is that, if high-pressure nitrogen gas is used, unlike the compressed air in the factory, there is no occurrence of pressure fluctuation and This is because the fluid pressure drive valve can be operated. In addition, by adopting the fluid pressure driven valve opening / closing system as described above, the solenoid valve 12 is “closed” in the event of a malfunction of the control device, and argon gas is supplied, which is safe. In addition, the supply pressure of nitrogen gas should just be about 0.5 MPa.
[0014]
Although the embodiment of the present invention described above has been described with respect to heating of a magnesium alloy material, the present invention can also be applied to heat treatment of a magnesium alloy material, flammable metal and its alloy material.
[0015]
【Effect of the invention】
The present invention described above has the following effects.
Even when the heating temperature of the magnesium alloy material exceeds the target temperature, the heating heater is stopped at the abnormal temperature T1 lower than the ignition temperature, and when the abnormal temperature T2 higher than the abnormal temperature T1 and lower than the ignition temperature is reached, the heating furnace Since the two-stage safety control of injecting an inert gas such as argon gas into the inside is performed, combustion due to ignition of the magnesium alloy material can be reliably prevented .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a heating furnace of the present invention.
FIG. 2 is an explanatory diagram showing an example of a control system diagram and a piping route diagram of the heating furnace of the present invention.
[Explanation of symbols]
1: Heating furnace 2: Furnace 3: Chain conveyor 4: Transport plate 5: Magnesium alloy material 6: Heater 7a: Temperature sensor for control 7b: Temperature sensor for monitoring 8: Nozzle 9: Cover 10: Controller 11: Fluid pressure drive valve 12: Solenoid valve 13: Inert gas storage container 14: Nitrogen gas storage container 15a, 15b: Piping 16: Piping

Claims (6)

In the heating control method of the magnesium alloy material charged in the heating furnace, an abnormal temperature T1 in which the temperature in the heating furnace is 10 to 20 ° C. higher than a target temperature T0 set in advance for performing forging, press molding or heat treatment ; the stops the heating of the heating furnace, the temperature in the heating furnace after stopping the heating becomes abnormal temperature T2 set 20 to 30 ° C. lower advance than the ignition temperature of higher and the alloy than the abnormal temperature T1, the furnace A method for controlling the heating of a magnesium alloy material, wherein an inert gas is injected into the inside. A heating furnace for heating a charged magnesium alloy material, a temperature sensor installed to detect the temperature in the heating furnace, and an inert gas injection capable of injecting an inert gas into the heating furnace a device, receives the temperature information of the temperature sensor, the heating means than the target temperature T0 becomes 10 to 20 ° C. higher abnormal temperature T1 set in advance in order to perform the forging or press forming or heat treatment issues a heating stop command, the abnormal temperature And a control device having a logic unit that issues a command to inject the inert gas into the inert gas injection device when the preset abnormal temperature T2 is higher than T1 and lower by 20 to 30 ° C. than the ignition temperature of the alloy. A heating furnace characterized by that.   The heating furnace according to claim 2, wherein a plurality of temperature sensors are installed so as to be located 20 to 50 mm away from the magnesium alloy material.   4. The inert gas injection device according to claim 2, further comprising: a fluid pressure driven valve that opens and closes according to a command from a control device in a pipe that connects the container for storing the inert gas and the inside of the heating furnace. heating furnace.   The heating furnace according to claim 4, wherein the fluid of the fluid pressure driven valve is nitrogen gas supplied from a container for storing nitrogen gas.   The heating furnace according to any one of claims 2 to 5, wherein the inert gas is argon gas.

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