CN118127290A - Atmosphere heat treatment furnace - Google Patents
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- CN118127290A CN118127290A CN202311632933.8A CN202311632933A CN118127290A CN 118127290 A CN118127290 A CN 118127290A CN 202311632933 A CN202311632933 A CN 202311632933A CN 118127290 A CN118127290 A CN 118127290A
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- 238000010438 heat treatment Methods 0.000 title claims abstract description 74
- 238000001514 detection method Methods 0.000 claims description 23
- 230000001105 regulatory effect Effects 0.000 claims description 21
- 230000005540 biological transmission Effects 0.000 claims description 13
- 230000005856 abnormality Effects 0.000 claims description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 7
- 229910052799 carbon Inorganic materials 0.000 claims description 7
- 238000004364 calculation method Methods 0.000 claims description 5
- 230000002159 abnormal effect Effects 0.000 claims description 3
- 238000013459 approach Methods 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 118
- 238000010586 diagram Methods 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 238000001816 cooling Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000000605 extraction Methods 0.000 description 4
- 239000000446 fuel Substances 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000002737 fuel gas Substances 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- 238000000137 annealing Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000009699 differential effect Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 230000009545 invasion Effects 0.000 description 1
- 238000012886 linear function Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
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Abstract
An atmosphere heat treatment furnace comprising: a furnace pressure control unit including a pressure detector for detecting a furnace pressure, a pressure-adjusting gas introduction unit, and a pressure controller for controlling an introduction amount of the pressure-adjusting gas introduced into the furnace by the pressure-adjusting gas introduction unit, the furnace pressure control unit performing sequential control to set the introduction amount of the pressure-adjusting gas to a predetermined amount when a difference between a detected temperature detected by the temperature detector and a target temperature is equal to or greater than a predetermined value, and performing feedback control to adjust the introduction amount of the pressure-adjusting gas by feeding back the detected pressure detected by the pressure detector when the difference between the detected temperature and the target temperature is less than the predetermined value.
Description
Technical Field
The present invention relates to an atmosphere heat treatment furnace suitable for heat treatment of steel materials and the like.
Background
In an atmosphere heat treatment furnace using endothermic gas, a decrease in furnace pressure may cause problems such as atmosphere deterioration due to invasion of external air and abnormal combustion. Therefore, in the atmosphere heat treatment furnace of the related art, a constant amount of an inert gas such as N 2 is supplied as a pressure-adjusting gas into the furnace so that the furnace pressure is higher than the atmospheric pressure (for example, see patent document 1 below).
However, the furnace pressure fluctuates due to heating and cooling conditions and the amount of the supplied endothermic gas, and the furnace pressure decreases during cooling or when the endothermic gas is not supplied. For example, when attempting to maintain the furnace pressure during cooling by supplying a constant amount of pressure regulating gas, it may result in an excess of pressure regulating gas being supplied to the furnace during heating. The excessive gas feed causes an increase in the amount of inert gas (pressure-adjusting gas) used and dilution of the endothermic gas, resulting in an increase in the running cost.
Patent document 1: JP2010-132997A
Disclosure of Invention
In view of the background of the above circumstances, an object of the present invention is to provide an atmosphere heat treatment furnace capable of maintaining a furnace pressure equal to or greater than atmospheric pressure to prevent external air from entering the furnace and to prevent excessive use of pressure-regulating gas.
Therefore, the atmospheric heat treatment furnace according to the first aspect of the present invention is defined as follows.
That is, the atmosphere heat treatment furnace according to the first aspect of the invention is an atmosphere heat treatment furnace comprising:
A furnace body;
A furnace atmosphere control unit configured to adjust a flow rate of an atmosphere adjustment gas supplied into the furnace such that an index value of a carbon potential determined based on a concentration of CO and a concentration of CO 2 in the furnace atmosphere is a predetermined value;
A furnace temperature control unit, which comprises
A temperature detector configured to detect a furnace temperature,
A heating unit, and
A temperature controller configured to adjust a control output to the heating unit such that a detected temperature received from the temperature detector approaches a target temperature; and
A furnace pressure control unit comprising
A pressure detector configured to detect a furnace pressure,
Pressure-regulating gas introduction unit, and
A pressure controller configured to adjust an introduction amount of the pressure-adjusting gas introduced into the furnace by the pressure-adjusting gas introduction unit,
Wherein when the difference between the detected temperature detected by the temperature detector and the target temperature is equal to or greater than a predetermined value, or when the control output to the heating unit is equal to or greater than a predetermined value, the furnace pressure control unit performs sequential control to set the introduction amount of the pressure-adjusting gas to a predetermined amount, and
When the difference between the detected temperature and the target temperature is smaller than a predetermined value, or when the control output to the heating unit is smaller than a predetermined value, the furnace pressure control unit performs feedback control to adjust the introduction amount of the pressure-regulated gas by feeding back the detected pressure detected by the pressure detector.
According to the atmosphere heat treatment furnace in the first aspect defined in this way, since the introduction amount of the pressure-adjusting gas is adjusted by feeding back the detected pressure, the amount of the pressure-adjusting gas used can be reduced as compared with the case where a constant amount of the pressure-adjusting gas is continuously introduced into the furnace.
Here, it is recognized that the detection value (detection pressure) detected by the pressure detector may have a large variation in a specific heating state. In the atmosphere heat treatment furnace according to the first aspect, since sequential control and feedback control are used in accordance with the heating state, wherein the sequential control does not use the detection value detected by the pressure detector, and the feedback control uses the detection value detected by the pressure detector, the furnace pressure can be maintained equal to or greater than the atmospheric pressure to prevent the outside air from entering the furnace and to prevent the excessive use of the pressure-regulating gas, while avoiding the problem caused by the variation in the detection value of the furnace pressure.
Here, a plurality of pressure detectors may be included.
In this case, the furnace pressure control unit may further include a low value selector configured to select a smallest detection value from the detection values received by the respective pressure detectors, and output the smallest detection value as the detection pressure in the furnace (second aspect).
Further, in the case of including a plurality of pressure detectors, the furnace pressure control unit may further include a transmission abnormality determination unit configured to determine that the transmission from the pressure detectors is abnormal when a state in which a difference between detection values transmitted from two selected pressure detectors is equal to or greater than a predetermined value continues for a predetermined time or longer (third aspect).
A fourth aspect of the present invention is defined as follows.
That is, in the atmosphere heat treatment furnace defined in any one of the first to third aspects, the atmosphere heat treatment furnace further includes:
A gas introduction pipe configured to introduce an atmosphere-adjusting gas and a pressure-adjusting gas into the furnace;
a flow rate detector configured to detect a flow rate of the atmosphere-adjusting gas;
A valve opening calculating unit configured to calculate, as a control output, a valve opening of the pressure-regulated gas supply unit required for preventing flashback in the gas introduction pipe; and
And a high value selector configured to output a larger control output of the control output calculated by the feedback control and the control output calculated by the valve opening degree calculation unit as a control output of the pressure-regulated gas supply unit.
According to the atmosphere heat treatment furnace of the fourth aspect defined in this way, since at least the flow rate required to avoid the tempering phenomenon is maintained in the gas introduction pipe, the tempering phenomenon can be avoided when the introduction amount of the pressure-adjusting gas is reduced by the feedback control.
Drawings
Fig. 1 is a schematic overall configuration diagram of an atmosphere heat treatment furnace according to an embodiment of the present invention.
Fig. 2 shows a schematic view of elements related to furnace temperature control of the atmosphere heat treatment furnace of fig. 1.
Fig. 3 shows a schematic view of elements related to furnace atmosphere control and furnace pressure control in the atmosphere heat treatment furnace of fig. 1.
Fig. 4 is a functional block diagram for explaining the structure of the pressure controller.
Fig. 5 is a functional block diagram for explaining the structure of the feedback control execution unit in fig. 4.
Fig. 6A, 6B and 6C show a change in detected pressure and a heating pattern in heat treatment using an atmosphere heat treatment furnace according to an embodiment of the present invention.
Fig. 7A and 7B show a modification of the function further added for preventing flashback in the gas introduction tube.
Fig. 8A and 8B illustrate a variation in which multiple pressure detectors are provided.
Fig. 9 shows an alarm output unit in the case where a plurality of pressure detectors are provided.
Detailed Description
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a schematic overall configuration diagram of an atmosphere heat treatment furnace according to an embodiment of the present invention. In fig. 1, reference numeral 10 denotes an intermittent atmosphere heat treatment furnace for annealing coils, steel strips, and the like, in which a heating chamber 13 is formed inside a box-shaped furnace body 12. An inlet/outlet 14 is formed at one end in the longitudinal direction of the furnace body 12, and a workpiece as an object to be heated is to be introduced into the furnace (heating chamber 13) through the inlet/outlet 14 via a roller group 15. Note that the inlet/outlet 14 may be opened and closed by a door 17 connected to the driving device 16.
A plurality of radiant tube burners 20 and ceiling fans 24 are disposed in the heating chamber 13 in the conveying direction (longitudinal direction), and a gas introduction tube 19 for introducing various gases is connected to the heating chamber 13.
Fig. 2 shows a schematic diagram of the elements related to furnace temperature control in the atmosphere heat treatment furnace 10. As shown in fig. 2, the atmosphere heat treatment furnace 10 includes a temperature detector 26, a plurality of radiant tube burners 20 as heating units, and a temperature controller 43. These constitute a furnace temperature control unit 45 in the present invention.
The temperature detector 26 detects the furnace temperature and transmits temperature information to the temperature controller 43. The type of the temperature detector 26 is not particularly limited, and a known thermocouple, radiation thermometer, or the like may be used in view of a measurable range, responsiveness, or the like.
The radiant tube burner 20 includes a tubular tube body 21 and a burner 22 coaxially disposed in a hollow portion of one end side of the tube body 21. The fuel supply pipe 30 and the air supply pipe 36 are connected to the burner 22, the flow rate adjustment valve 33 is provided on the main pipe 31 side of the fuel supply pipe 30, and the flow rate adjustment valve 39 is provided on the main pipe 37 side of the air supply pipe 36. Manual valves 34 and 40 are provided in the respective branch pipes 32 and 38 of the fuel supply pipe 30 and the air supply pipe 36, and the valve opening is adjusted in advance so that the fuel gas and the combustion air are uniformly supplied to each burner 22.
The temperature controller 43 adjusts the control output of the radiant tube burner 20 such that the detected temperature received from the temperature detector 26 approaches a preset thermal mode (target temperature) during operation. Control signals corresponding to such control outputs are sent to the flow rate adjustment valves 33 and 39 to increase or decrease the opening degrees of these flow rate adjustment valves 33 and 39, thereby controlling the heating power of the burner 22. When cooling the furnace interior, the supply of the fuel gas is stopped, and only air is allowed to flow through the tube 21.
In the present embodiment, the temperature controller 43 outputs information about the difference between the detected temperature detected by the temperature detector 26 and the target temperature to the pressure controller 72 described later.
Such a temperature controller 43 may be implemented by, for example, a Programmable Logic Controller (PLC) including a data processing unit, a storage unit, and a communication I/F unit, or by a temperature regulator. Note that the atmosphere controller 66 and the pressure controller 72, which will be described later, may also be similarly implemented by a PLC or various regulators.
Next, furnace atmosphere control will be described. In the embodiment of the present invention, an endothermic modifying gas is used as an atmosphere gas. The endothermic modifying gas is generally called RX gas, and contains CO, H 2, and N 2 as main components. In the embodiment of the present invention, by PF control, which uses RX gas and controls an index value (PF) of carbon potential, which is determined from the ratio of the square of CO% to CO 2% in furnace atmosphere gas based on the following formula (1), as a target value, an atmosphere in which decarburization and carburization do not occur in the furnace can be obtained.
PF= (CO%) 2/CO2% equation (1)
As shown in fig. 3, RX gas supply pipes 47, N 2 gas supply pipes 48, 49, and 50, and an air supply pipe 51 are connected to a gas introduction pipe 19, the gas introduction pipe 19 is connected to the furnace body 12, a check valve 54 is connected to a gas feed pipe 53, and the gas feed pipe 53 is connected to the furnace body 12.
The RX gas supply pipe 47 supplies the RX gas generated by the RX gas generator 56 to the gas introduction pipe 19, and introduces the RX gas into the furnace through the gas introduction pipe 19, and the flow rate adjustment valve 58 and the flow rate detector 59 are interposed between the gas supply pipe 47 and the gas introduction pipe 19.
The N 2 gas supply pipe 49 supplies N 2 gas from the N 2 gas supply source 61 to the gas introduction pipe 19, and introduces N 2 gas into the furnace through the gas introduction pipe 19, with the flow rate adjustment valve 64 interposed between the N 2 gas supply pipe 49 and the gas introduction pipe 19.
The air supply pipe 51 supplies air from the air supply source 62 into the furnace through the gas introduction pipe 19, and the flow rate adjustment valve 63 is interposed between the air supply pipe 51 and the gas introduction pipe 19.
These RX gas supply pipe 47, N 2 gas supply pipe 49 and air supply pipe 51 are used to introduce various gases into the furnace in PF control using an index value (PF) of carbon potential.
In fig. 3, reference numeral 65 denotes an analyzer, and reference numeral 66 denotes an atmosphere controller.
The analyzer 65 measures the CO 2 gas concentration (CO 2%) and the CO gas concentration (CO%) in the furnace and sends measurement signals to the atmosphere controller 66.
The atmosphere controller 66 is connected to the flow regulating valves 58, 64 and 63 on the analyzer 65, the RX gas supply pipe 47, the N 2 gas supply pipe 49 and the air supply pipe 51. The atmosphere controller 66 receives the measurement signal from the analyzer 65, calculates an index value (PF) of the carbon potential shown in formula (1), and further calculates a control output corresponding to the opening degree of each flow rate adjustment valve such that the PF value calculated as above, which is actually measured, follows a reference value (PF setting mode shown in fig. 6B) of the index value of the carbon potential, which is preselected according to the furnace temperature in the atmosphere heat treatment furnace 10 and the heat treatment content of the work piece. Then, control signals corresponding to these control outputs are input to the respective flow rate adjustment valves 58, 64 and 63, and the flow rates of RX gas, N 2 gas and air introduced into the furnace are adjusted by these flow rate adjustment valves.
Next, the oven pressure control will be described. In this embodiment, the control for maintaining the furnace pressure equal to or greater than the atmospheric pressure is performed separately from the above-described PF control. In this case, the pressure detector 68, the N 2 gas supply pipe 48, and the pressure controller 72 shown in fig. 3 are used.
The pressure detector 68 detects the furnace pressure and transmits a signal corresponding to the detected pressure value (detected value). The detection value may be absolute pressure or a pressure difference from atmospheric pressure. As the pressure detector 68, for example, a pressure gauge may be used.
During furnace pressure control, the N 2 gas supply pipe 48 supplies N 2 gas from the N 2 gas supply source 61 to the gas introduction pipe 19, and N 2 gas is introduced into the furnace through the gas introduction pipe 19, and the flow rate adjustment valve 69 is interposed between the N 2 gas supply pipe 48 and the gas introduction pipe 19. The gas introduction pipe 19, the N 2 gas supply pipe 48, and the flow rate regulating valve 69 correspond to the pressure regulating gas introduction unit according to the present invention.
The pressure controller 72 is connected to the temperature controller 43, the pressure detector 68, and the flow rate adjustment valve 69 on the N 2 gas supply pipe 48, and outputs a control output corresponding to the valve opening degree to the flow rate adjustment valve 69.
As shown in fig. 4, the pressure controller 72 includes a control switching unit 74, a sequential control execution unit 75, and a feedback control execution unit 76.
The sequence control execution unit 75 outputs a predetermined control output to the flow rate adjustment valve 69 as a control output.
On the other hand, as shown in fig. 5, the feedback control execution unit 76 includes a PID control system composed of a proportional action unit 77A, an integral action unit 77B, a differential action unit 77C, and an addition unit 77D, executes feedback control based on a difference between the target pressure value SP1 set by the target pressure setting unit 78 and the detected pressure value PV1 from the pressure detector 68, and calculates a control output MV1 (0% +.mv1+.ltoreq.100%) output to the flow rate adjustment valve 69.
When the control output to the flow rate regulating valve 69 is obtained, the control switching unit 74 determines which of the sequential control execution unit 75 and the feedback control execution unit 76 performs control based on the heating information received from the temperature controller 43.
Specifically, when the difference between the detected temperature and the target temperature is equal to or greater than a predetermined value in the heating information received from the temperature controller 43 (i.e., when the change in the detected pressure is large), the sequential control execution unit 75 outputs a predetermined control output and executes sequential control to set the introduction amount of the pressure-adjusting gas to a predetermined amount.
On the other hand, when the difference between the detected temperature and the target temperature is smaller than the predetermined value (i.e., when the change in the detected pressure is small), the feedback control performing unit 76 feeds back the detected pressure to calculate a control output, and performs feedback control to adjust the introduction amount of the pressure-regulated gas.
Thus, in the embodiment of the present invention, the pressure detector 68, the pressure controller 72, and the gas introduction pipe 19, the N 2 gas supply pipe 48, and the flow rate regulating valve 69 corresponding to the pressure regulating gas introduction unit form the furnace pressure control unit 80 according to the present invention.
Next, a control operation when heat treatment (for one batch) is performed in the atmosphere heat treatment furnace 10 will be described.
When the door 17 is closed and a series of heat treatments is started after the workpiece as an object to be heated is loaded into the furnace (heating chamber 13) through the inlet/outlet 14, N 2 gas for purging is introduced into the furnace through the N 2 gas supply pipe 49, and the heating pattern shown in fig. 6A is started to be followed by the atmosphere heating using the burner 20. In contrast, at the start of heating (a portion indicated by t1 in fig. 6A), the inside of the furnace is in a low temperature range, the temperature difference between the target temperature and the detected temperature based on the heating mode is large, a control output of nearly 100% is output from the temperature controller 43 to the burner 20, and rapid heating is performed.
In a state where such rapid heating is performed, as shown in fig. 6C, there is a case where the detected value detected by the pressure detector 68 fluctuates too much to obtain an accurate furnace pressure. Therefore, during this time, the furnace pressure control unit 80 performs sequential control and introduces a predetermined amount of pressure-regulating gas into the furnace to maintain the furnace pressure equal to or greater than the atmospheric pressure and prevent external air from entering the furnace. Note that the introduction amount of the pressure-adjusting gas by sequential control may be set to a constant flow rate per hour.
Next, when the temperature in the furnace atmosphere increases and the temperature difference between the target temperature and the detected temperature based on the heating mode is small (a portion indicated by t2 in fig. 6A), the RX gas starts to be introduced in the setting mode of the index value based on the carbon potential (the PF setting mode shown in fig. 6B). When the portion t2 is entered, the change in the detection value detected by the pressure detector 68 decreases, and thus the furnace pressure control unit 80 performs feedback control to adjust the introduction amount of the pressure-regulated gas. The amount of the pressure-adjusting gas (the amount of N 2 gas) introduced by the pressure-adjusting gas supply unit can be reduced in accordance with the increase in the furnace pressure caused by the thermal expansion of the atmosphere gas and the increase in the furnace pressure caused by the introduction of the RX gas into the furnace while the feedback control is performed.
In this way, according to the atmosphere heat treatment furnace 10 of the embodiment of the present invention, since sequential control and feedback control are used according to the heating state, in which the sequential control does not use the detection value detected by the pressure detector 68, and the feedback control uses the detection value detected by the pressure detector 68, the furnace pressure can be maintained equal to or greater than the atmospheric pressure to prevent the outside air from entering the furnace and to prevent excessive use of the pressure-regulating gas, while avoiding problems due to variations in the detection value of the furnace pressure.
Next, modifications of the embodiment of the present invention will be described.
Fig. 7A and 7B show modifications to which a function for preventing flashback in the gas introduction tube 19 is further added. In the case where air and RX gas are simultaneously supplied into the furnace through the gas introduction pipe 19, when the total flow rate of the gas flowing through the gas introduction pipe 19 is too small, there is a risk of a phenomenon in which flames flow back through the gas introduction pipe 19 (flashback phenomenon). In order to prevent such a flashback phenomenon, it is necessary to increase the opening degree of the flow rate regulating valve 69 as the pressure regulating gas introducing unit to keep the flow rate equal to or greater than a certain level.
As shown in fig. 7A and 7B, in this modification, a valve opening degree calculation unit 82 and a high value selector 84 are added to the pressure controller 72.
The valve opening degree calculation unit 82 outputs the opening degree of the flow rate adjustment valve 69 as the pressure adjustment gas introduction unit, which is necessary for preventing the flashback phenomenon. Based on a linear function showing a relation between the flow rate of RX gas obtained in advance and the opening degree of the flow rate adjustment valve 69 as the pressure adjustment gas introduction unit (see fig. 7B), the valve opening degree calculation unit 82 outputs the opening degree of the flow rate adjustment valve 69 required to prevent the flashback phenomenon as a control output MV2 (0% +.mv2+.ltoreq.100%) based on the flow rate information of the RX gas. Then, when the control output MV2 obtained by the valve opening-degree calculating unit 82 and the control output MV1 calculated by the furnace pressure control are input to the high-value selector 84, the high-value selector 84 outputs the larger of the two control outputs as the control output to the flow rate regulating valve 69.
Therefore, since at least the flow rate required to avoid the flashback phenomenon is maintained in the gas introduction pipe 19, the flashback phenomenon can be avoided when the amount of N 2 gas for maintaining the furnace pressure is reduced by the feedback control.
Next, another modification different from the embodiment of fig. 7A and 7B will be described.
The atmosphere heat treatment furnace according to the above embodiment is provided with one pressure detector, but a plurality of pressure detectors may be provided as the case may be. In this case, from the viewpoint of preventing outside air from entering the furnace, it is desirable to use the smallest detected value among the detected values received from the respective pressure detectors as the detected furnace pressure.
For example, as shown in fig. 8A, when two pressure detectors 68A and 68B are provided for detecting the furnace pressure, as shown in fig. 8B, a signal extraction unit 86 and a low value selector 88 are provided in the pressure controller 72, signals of detected values transmitted from the pressure detectors 68A and 68B are extracted by the signal extraction unit 86 at predetermined sampling intervals (for example, 100 ms) and a predetermined number of moving average items (for example, 10) to obtain moving average values, and the low value selector 88 that receives these moving average values outputs the smallest moving average of the received moving average values as the detected furnace pressure.
Further, when the furnace pressure is detected using the two pressure detectors 68A and 68B, as shown in fig. 9, an alarm output unit 90 may also be provided to detect and alarm a transmission abnormality caused by a failure of the pressure detectors themselves.
The alarm output unit 90 in fig. 9 includes a signal extraction unit 91 and a transmission abnormality determination unit 92. The signal extraction unit 91 extracts the signals of the detection values transmitted from the pressure detectors 68A and 68B at a predetermined sampling interval (for example, 100 ms) and a predetermined number of moving average items (for example, 10) to obtain a moving average value, and sends the obtained signals of the moving average value to the transmission abnormality determination unit 92.
The transmission abnormality determination unit 92 compares the two moving average values, and when the state in which the difference is equal to or greater than a predetermined value continues for a predetermined time or longer, determines that there is a transmission abnormality from the specific pressure detector, and outputs a transmission abnormality detection signal.
In fig. 9, reference numeral 95 denotes an AND calculator, reference numeral 94 denotes a NOT calculator, AND reference numeral 96 denotes an on-delay timer (on-DELAY TIMER). The alarm output unit 90 may receive not only the signals from the pressure detectors 68A and 68B, but also the signal during the heat treatment, the door closing completion signal, and the off signal from the pressure detectors 68A and 68B; and outputs an alarm output signal when the transmission abnormality detection signal is output from the transmission abnormality determination unit 92 in a state where the signal during the heat treatment and the gate closing completion signal are received without receiving the disconnection signal. Note that, in a period of time after the door is closed and the heat treatment is started, as shown in fig. 6C, since the fluctuation of the detected pressure is large, alarm monitoring is performed after the set time for waiting for stabilization set by the on-delay timer 96 has elapsed.
By using the alarm output unit 90 configured in this way, it can be known from the alarm output signal that one of the pressure detectors 68A and 68B has a high possibility of failure.
As described above, the embodiment in fig. 9 is an embodiment with two pressure detectors. Even when the number of pressure detectors is three or more, a failure of the pressure detectors can be detected by comparing the pressure detectors in groups of two.
Although the embodiment of the present invention has been described in detail above, it is merely an example, and the present invention may be configured in various forms without departing from the scope of the invention.
(1) For example, in the above-described embodiment, the difference between the detected temperature and the target temperature is used as the heating information to appropriately use the sequential control and the feedback control. Or control output information of the heating unit (burner) may be used.
(2) Further, the above-described embodiment is an atmosphere heat treatment furnace in which the inlet/outlet is formed at one end side in the longitudinal direction of the furnace body. Or the present invention may be applied to a through-type atmosphere heat treating furnace in which an inlet is provided at one end and an outlet is provided at the other end in the longitudinal direction of the furnace body. In this case, pressure detectors may be provided in the vicinity of the inlet side and the vicinity of the outlet side, respectively.
The present application is based on japanese patent application No.2022-193501 filed on month 2 of 2022, 12, the contents of which are incorporated herein by reference.
List of reference numerals
10 Atmosphere heat treatment furnace
12 Furnace body
19 Gas inlet pipe
20 Radiant tube burner (heating unit)
26 Temperature detector
43 Temperature controller
45 Furnace temperature control unit
48N 2 gas supply pipe (pressure regulating gas introducing unit)
59 Flow detector
66 Atmosphere controller
69 Flow regulating valve (pressure regulating gas introducing unit)
68 Pressure detector
72 Pressure controller
80 Furnace pressure control unit
82 Valve opening degree calculating unit
84 High value selector
88 Low value selector
92 Transmission abnormality determination unit
MV1 and MV2 control output
Claims (4)
1. An atmosphere heat treatment furnace comprising:
A furnace body;
A furnace atmosphere control unit configured to adjust a flow rate of an atmosphere adjustment gas supplied into the furnace such that an index value of a carbon potential determined based on a concentration of CO and a concentration of CO 2 in the furnace atmosphere is a predetermined value;
A furnace temperature control unit, which comprises
A temperature detector configured to detect a furnace temperature,
A heating unit, and
A temperature controller configured to adjust a control output to the heating unit such that a detected temperature received from the temperature detector approaches a target temperature; and
A furnace pressure control unit comprising
A pressure detector configured to detect a furnace pressure,
Pressure-regulating gas introduction unit, and
A pressure controller configured to adjust an introduction amount of the pressure-adjusting gas introduced into the furnace by the pressure-adjusting gas introduction unit, wherein
When the difference between the detected temperature detected by the temperature detector and the target temperature is equal to or greater than a predetermined value, or when the control output to the heating unit is equal to or greater than a predetermined value, the furnace pressure control unit performs sequential control to set the introduction amount of the pressure-adjusting gas to a predetermined amount, and
When the difference between the detected temperature and the target temperature is smaller than the predetermined value, or when the control output to the heating unit is smaller than the predetermined value, the furnace pressure control unit performs feedback control to adjust the introduction amount of the pressure-adjusting gas by feeding back the detected pressure detected by the pressure detector.
2. The atmosphere heat treatment furnace according to claim 1, further comprising:
a plurality of the pressure detectors, wherein
The furnace pressure control unit further includes a low value selector configured to select a smallest detection value from detection values received by the respective pressure detectors, and output the smallest detection value as a detection pressure in the furnace.
3. The atmosphere heat treatment furnace according to claim 1, further comprising:
a plurality of the pressure detectors, wherein
The furnace pressure control unit further includes a transmission abnormality determination unit configured to determine that transmission from the pressure detectors is abnormal when a state in which a difference between detection values transmitted from two selected pressure detectors is equal to or greater than a predetermined value continues for a predetermined time or longer.
4. The atmosphere heat treatment furnace according to claim 1, further comprising:
A gas introduction pipe configured to introduce the atmosphere-adjusting gas and the pressure-adjusting gas into the furnace;
A flow detector configured to detect a flow rate of the atmosphere-adjusting gas;
a valve opening calculating unit configured to calculate, as a control output, a valve opening of a pressure-regulated gas supply unit required for preventing flashback in the gas introduction pipe; and
A high value selector configured to output, as a control output of the pressure-regulated gas supply unit, a larger control output of the control output calculated by the feedback control and the control output calculated by the valve opening degree calculation unit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2022193501A JP2024080372A (en) | 2022-12-02 | Atmospheric heat treatment furnace | |
| JP2022-193501 | 2022-12-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN118127290A true CN118127290A (en) | 2024-06-04 |
Family
ID=91239607
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311632933.8A Pending CN118127290A (en) | 2022-12-02 | 2023-12-01 | Atmosphere heat treatment furnace |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN118127290A (en) |
-
2023
- 2023-12-01 CN CN202311632933.8A patent/CN118127290A/en active Pending
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