JP2016151517A - Carbon potential calculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calculation device in which abnormality such as sensor degradation occurred in oxygen sensors for detecting Oconcentration of atmosphere inside a furnace is detected.SOLUTION: The carbon potential calculation device comprises: a setting unit 20 that sets an input upper limit value of the Oconcentration to be detected by a sensor unit 10; a plurality of oxygen sensors 11 (first oxygen sensor 11a, second oxygen sensor 11b) that detect the Oconcentration of the atmosphere inside the furnace; and a determination unit 40 that compares a deviation difference which is a difference value of the Oconcentration detected by each of the oxygen sensors 11a, 11b, or a deviation difference which is a difference value of a CP value calculated using the Oconcentration detected by the oxygen sensors 11a, 11b, with an abnormality determination threshold stored in a storage unit 50, and determines that the oxygen sensor 11 has degraded when the deviation difference exceeds the abnormality determination threshold, and outputs an abnormal signal.SELECTED DRAWING: Figure 1

Description

The present invention relates to a carbon potential calculation device that calculates a carbon potential (CP value) of an atmosphere in a furnace based on an O ₂ concentration in a heat treatment furnace such as a carburizing furnace or a carbonitriding furnace.

  Conventionally, tempered steel is remarkably superior in terms of the combination of strength and toughness, but its wear resistance is inferior to that of carburized and quenched, and fatigue failure due to repeated stress is a problem. In such a component, the strength at the surface is important because fatigue cracks are generated near the surface. Therefore, from this point of view, a gas carburizing method is generally known as a surface hardening treatment for an article that requires strength against wear resistance and fatigue fracture.

  The gas carburizing method is a heat treatment furnace (continuous gas carburizing furnace or batch type gas carburizing furnace) that uses a mixed gas of hydrocarbon-based gas and air as a raw material for an endothermic or gas-generating furnace. Using the modified gas (endthermic gas) obtained by modification using the carrier gas as a carrier gas, an enriched gas (hydrocarbon gas such as propane or butane) for supplying a predetermined carbon potential is supplied into the carburizing chamber together with the carrier gas. The carbon potential is indirectly calculated by measuring the concentration or partial pressure of the gas components that make up the carburizing room atmosphere, and the amount of enriched gas supplied is adjusted based on the result. Carburization is controlled by this.

Then, for proper supply amount control of enriched gas in the heat treatment furnace, the CO ₂ concentration in the furnace atmosphere gas detected by the CO ₂ sensor, carbon potential (Carbon Potential Based on this CO ₂ concentration, or less, There is known a carbon potential calculation device that simply calculates a “CP value” (refer to Patent Document 1 below for details).

Japanese Patent No. 3973795

However, since the CO ₂ sensor used in the conventional carbon potential calculation device including the device of Patent Document 1 uses the infrared absorption method as the concentration detection method, it takes time to detect the CO ₂ concentration. There's a problem. Therefore, since the CO ₂ concentration used for calculating the CP value is a value delayed for a predetermined time immediately after detection, the CP value in the furnace atmosphere could not be observed in real time.

Further, since the CO ₂ sensor is very expensive, for example, when the heat treatment furnace is a continuous type, each treatment zone (preheating zone, carburizing zone, diffusion zone, temperature drop / holding zone, quenching zone) in the furnace is infrared. Since the detection unit is installed and the input voltage from each infrared detection unit is switched each time and detection processing is performed, the time until the CO ₂ concentration detected in the furnace atmosphere is known is further delayed. There was a problem that.

  Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a carbon potential calculation device capable of calculating a CP value in a heat treatment furnace to be measured in a state close to real time. Is.

In order to achieve the above object, the carbon potential calculating apparatus according to claim 1 is based on the O ₂ concentration, CO concentration, and temperature in the furnace atmosphere detected by a sensor unit installed in the heat treatment furnace. In the carbon potential calculation device for calculating the carbon potential (CP value) of the atmosphere,
A sensor unit having two oxygen sensors for detecting the atmosphere in the furnace;
A calculation processing unit that calculates a CP value using a CO concentration that is a preset fixed value and an O ₂ concentration detected by the sensor unit;
It is provided with.

The carbon potential calculation device according to claim 2 is the carbon potential calculation device according to claim 1,
The calculation processing unit includes deviation difference calculation means for calculating a deviation difference of a voltage value corresponding to the O ₂ concentration detected by each oxygen sensor,
It is characterized by comprising a determination unit for determining an abnormality and outputting an abnormality signal when the deviation difference calculated by the deviation difference calculating means exceeds a preset abnormality determination threshold value.

The carbon potential calculation device according to claim 3 is the carbon potential calculation device according to claim 1,
The calculation processing unit includes deviation difference calculation means for calculating a deviation difference between CP values calculated according to _two O ₂ concentrations detected by the oxygen sensors,
The apparatus includes a determination unit that determines an abnormality and outputs an abnormality signal when the deviation difference calculated by the deviation difference calculation means exceeds a preset abnormality determination threshold value.

  According to a fourth aspect of the present invention, there is provided the carbon potential calculation device according to the second or third aspect, further comprising an alarm unit that outputs an alarm to the outside when an abnormal signal is input from the determination unit. .

According to the carbon potential calculation apparatus of the present invention, the oxygen sensor provided as a sensor unit for detecting the state of the furnace atmosphere is superior in gas concentration detection response in the furnace atmosphere as compared to the CO ₂ sensor. When calculating the CP value in the furnace atmosphere, a value closer to real time can be obtained. In addition, since it is possible to detect the presence or absence of deterioration of the oxygen sensor based on the O ₂ concentration detected by each oxygen sensor, it is possible to perform maintenance immediately when the deterioration of the oxygen sensor is recognized.

It is a schematic block diagram which shows the structure of the carbon potential calculation apparatus which concerns on this invention. It is the schematic of the front panel of the apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited by this embodiment, and all other forms, examples, operation techniques, etc. that can be implemented by those skilled in the art based on this form are included in the scope of the present invention. .

The carbon potential calculation device (hereinafter simply referred to as “CP value calculation device”) of the present invention is a measurement target such as a gas concentration or temperature in a furnace atmosphere in a heat treatment furnace such as a carburizing furnace or a carbonitriding furnace. This device detects various conditions and calculates the carbon potential (CP value) in the furnace atmosphere. It has multiple oxygen sensors with excellent detection response, and calculates the CP value from the O ₂ concentration detected by the oxygen sensor. At the same time, the presence or absence of deterioration of the oxygen sensor is determined by using the O ₂ concentration detected by each oxygen sensor and the deviation difference of the CP value calculated from the O ₂ concentration.

  First, the configuration of the CP value calculation apparatus of this example will be described with reference to FIGS. As shown in FIG. 1 or FIG. 2, the CP value calculation apparatus 1 includes a sensor unit 10, a setting unit 20, a calculation processing unit 30, a determination unit 40, a storage unit 50, a display unit 60, and an alarm unit. 70.

The sensor unit 10 includes a plurality of oxygen sensors 11 (in this example, a first oxygen sensor 11a and a second oxygen sensor 11b) that detect the O ₂ concentration in the furnace atmosphere in the heat treatment furnace 100 to be measured by a voltage value (mV). ) And a temperature sensor 12 (three types of K thermocouple, R thermocouple, and S thermocouple in this example) for detecting the temperature (° C.) in the furnace atmosphere, and O ₂ detected by each sensor. The concentration and temperature value are output to the calculation processing unit 30.

  In FIG. 1, the sensor unit 10 includes one temperature sensor 12, but may be provided separately for each oxygen sensor 11. Further, in FIG. 1, the sensor unit 10 is described as a constituent requirement of the CP value calculation device 1, but actually the detection unit of the sensor unit 10 is arranged at a predetermined location of the heat treatment furnace 100, which is separate from the device. In this state, the CP value calculation device 1 is electrically connected.

Since the oxygen sensor 11 uses the oxygen ion conductivity of the zirconia solid electrolyte instead of the infrared absorption method like the CO ₂ sensor, the oxygen sensor 11 has excellent responsiveness at the time of gas concentration detection, for example, O ₂ in the furnace atmosphere. The time until acquiring the density is about 5 seconds. On the other hand, in view of the fact that it takes about several minutes until the CO ₂ sensor used in the conventional apparatus detects the CO ₂ concentration, the CP value acquired by this apparatus is compared with the conventional apparatus. It is possible to obtain a CP value closer to that immediately after density detection.

  As shown in FIG. 2, the setting unit 20 is composed of various operation keys provided in plural at predetermined locations on the front panel of the apparatus. Setting contents include CP values such as switching of display contents displayed on the display unit 13, selection setting of the oxygen sensor 11 in the sensor unit 10, and input setting of a CO concentration (fixed value) appropriately determined according to the gas used. Various settings related to the calculation process can be performed.

The calculation processing unit 30 uses the O ₂ concentration detected by the first oxygen sensor 11a and the second oxygen sensor 11b, the CO concentration set by the setting unit 20 and the CP value calculation formula stored in the storage unit 50 to calculate the CP value. Detected by the CP value calculation means 31 for calculating the difference in deviation of the O ₂ concentration (voltage value) from the first oxygen sensor 11a and the second oxygen sensor 11b input from the sensor unit 10 or by the oxygen sensors 11a and 11b. Displacement difference calculating means 32 for calculating a deviation difference of the CP value calculated by the CP value calculating means 31 based on the O ₂ concentration is provided.

The CP value calculation means 31 performs a CP value calculation process based on various detection data from the sensor unit 10 (O ₂ concentration and temperature in the furnace atmosphere) and the CO concentration (fixed value) set by the setting unit 20. ing.

Here, a calculation method of the CP value will be described. The CO concentration used in the CP value calculation process is appropriately set as a fixed value from the setting unit 20 depending on the type of gas used in the heat treatment furnace 100. In the following equations, “t” is the temperature (° C.) in the furnace atmosphere detected by the temperature sensor 12, and “CO” is the CO concentration that is a fixed value set by the setting unit 20. “PO ₂ ” is the oxygen partial pressure calculated from the O ₂ concentration in the furnace atmosphere.

First, As1 (saturated carbon content of austenite) is calculated using the following formula 1, and PO ₂ (oxygen partial pressure) measured using the following formula 2 is calculated. Next, As2 (saturated carbon content of austenite) is calculated from the relationship between the saturated carbon content of austenite and the temperature using the following equation 3 obtained by regression analysis.

Then, using the PO ₂ and As ₂ calculated in the above formulas ₂ and 3, the CP value is calculated from the following formula 4 or 5. In addition, when using Equation 5, the saturation carbon amount (As2) of austenite is added to the value obtained by dividing the CO concentration (CO) by the square root (PO ₂ 1/2) of the oxygen partial pressure calculated in Equation 2 above. Used when the obtained value (L) is L ≧ 2.7622.

And in this apparatus, any of the following determination processes 1-4 can be employ | adopted as a method of determining CP value. The determination processes 1 and 2 are processes when one of the two oxygen sensors 11 is selected. The determination processes 3 and 4 are processes when both the oxygen sensors 11a and 11b are used. A desired determination processing method is set from the setting unit 20.
(Decision process 1)
A method of selecting either one of two oxygen sensors 11 and calculating a CP value from the O ₂ concentration detected by the selected oxygen sensor 11.
(Decision process 2)
One of the two oxygen sensors 11 is selected, a CP value is calculated from the O ₂ concentration detected by the selected oxygen sensor 11, and a predetermined number of times before the calculated latest CP value (for example, five times). A method of using an average value of past data as a true CP value.
(Decision process 3)
When CP values corresponding to the respective O ₂ concentrations measured by the first oxygen sensor 11a and the second oxygen sensor 11b are calculated and the deviation difference determination result by the determination unit 40 is within the normal range, two CP values are obtained. The value obtained by averaging the values is used as the true CP value.
(Decision process 4)
Of the CP values calculated according to the respective O ₂ concentrations detected by the first oxygen sensor 11a and the second oxygen sensor 11b, average values of past data from the latest CP value to a predetermined number of times (for example, five times) are obtained. A method of using the value obtained by further averaging the two obtained CP values as the true CP value.

The deviation difference calculating means 32 calculates the deviation difference of each O ₂ concentration (voltage value) detected by the first oxygen sensor 11a and the second oxygen sensor 11b and outputs it to the determination unit 40. Further, the deviation difference calculation means 32 calculates the deviation difference of the CP value calculated by the CP value calculation means 31 based on the O ₂ concentration detected by each sensor of the sensor unit 10 and outputs it to the determination unit 40. The deviation difference calculating means 32 is configured to calculate the absolute value of the difference value of the O ₂ concentration (voltage value) detected by the first oxygen sensor 11a and the second oxygen sensor 11b or the CP value calculated from the two O ₂ concentrations. The absolute value of the difference value is “deviation difference”.

The deviation difference calculation means 32 of this example is the above-described two types of deviation difference calculation processing (that is, processing for calculating deviation of O ₂ concentration (potential difference) or processing for calculating deviation of CP value). However, a configuration in which the user arbitrarily selects a processing method from the setting unit 20 and executes the selected processing method may be employed.

  The determination unit 40 compares the deviation difference calculated by the deviation difference calculation unit 32 with the abnormality determination threshold value stored in the storage unit 50, and when the deviation difference exceeds the abnormality determination threshold value. It is determined that any one of the oxygen sensors 11 has deteriorated, and an abnormal signal is output to the alarm unit 70.

The determination processing contents of the determination unit 40 will be described in detail. The deviation difference calculated by the deviation difference calculation unit 32 is compared with the abnormality determination threshold value stored in the storage unit 50. It is determined whether or not the number is exceeded. At this time, when the deviation difference exceeds the abnormality determination threshold, one or both of the first oxygen sensor 11a and the second oxygen sensor 11b are deteriorated and an accurate O ₂ concentration cannot be detected. In order to determine and notify the user of the deterioration of the oxygen sensor 11, an abnormal signal is output to the alarm unit 70. On the other hand, when the deviation difference does not exceed the abnormality determination threshold value, it is determined that the deterioration of the oxygen sensor 11 is not recognized, and no abnormality signal is output.

As described above, the determination unit 40 functions as a function for determining whether or not the oxygen sensor 11 has deteriorated. The deviation difference obtained by directly comparing the O ₂ concentrations (voltage values) detected by the oxygen sensors 11a and 11b or the oxygen sensors 11a. The deviation difference obtained by comparing the CP values calculated based on the O ₂ concentration detected in 11b is compared with a preset abnormality determination threshold, and oxygen is determined depending on whether the deviation difference exceeds the abnormality determination threshold. Whether or not the sensor 11 has deteriorated can be determined. In addition, since a plurality of oxygen sensors 11 are provided, a more accurate CP value can be obtained by using the above-described CP value determination method.

The storage unit 50 includes various storage devices. In addition to the abnormality determination threshold used by the determination unit 40 for abnormality determination, the storage unit 50 includes a drive control program necessary for driving and controlling each unit included in the CP value calculation device 1. Remember. Further, depending on the specification of the CP value determination process described above, the storage unit 50 stores the past data (predetermined number of times) of the O ₂ concentration detected by the oxygen sensor 11 and the past data (predetermined number of times) of the calculated CP value. You may make it do.

As shown in FIG. 2, the display unit 60 includes a light emitting display device that displays numerical values or characters in a plurality of seven segments and various display devices such as LEDs (light emitting diodes). In addition to the configuration shown in FIG. 2, the display unit 60 may be configured by a liquid crystal display, an inorganic or organic EL display, or the like. The display unit 60 is lit / flashed according to various settings from the setting unit 20 or an alarm output from the alarm unit 70. Further, the display unit 60, corresponding display of CP value based on O ₂ concentration calculated in the calculation processing unit 30, such as has been the O ₂ concentration and temperature detected by the sensor unit 10 to the setting by the setting unit 20 form Is displayed.

  The alarm unit 70 is configured by a sounding device such as a buzzer or a display device such as an LED, for example. When an abnormal signal is input from the determination unit 40, an alarm output (sounding, lighting / blinking, etc.) for notifying the outside is provided. I do. Further, the alarm unit 70 may be a personal computer (PC) used when a manager who manages the heat treatment furnace 100 monitors the operation state of the furnace.

In the CP value calculation apparatus 1 described above, the O ₂ concentration in the furnace atmosphere in the heat treatment furnace 100 detected by the oxygen sensor 11, the temperature in the furnace atmosphere detected by the temperature sensor 12, and the setting unit 20 are set. The CP value is calculated by the calculation processing unit 30 based on the CO concentration.

Further, when determining whether or not the oxygen sensor 11 has deteriorated, calculation is based on the deviation of the O ₂ concentration (voltage value) detected by the first oxygen sensor 11a and the second oxygen sensor 11b or the detected O ₂ concentration. The deviation difference of the CP value is compared with the abnormality determination threshold value stored in the storage unit 50. Then, when the deviation difference exceeds the abnormality determination threshold, it is determined that any of the oxygen sensors 11 is deteriorated, and an abnormality signal is output to the alarm unit 70 to notify the outside that there is an abnormality.

As described above, the above-described CP value calculation apparatus 1 has a plurality of oxygen sensors 11 (first oxygen sensor 11a and second oxygen sensor 11b) that have better gas concentration detection response than the CO ₂ sensor used in the conventional apparatus. ) comprising a, also deviation which is a difference value of each oxygen sensor 11a, the detected O ₂ concentration excursion difference or the oxygen sensor 11a is a difference value, CP value calculated from the O ₂ concentration detected by 11b and 11b The difference is compared with the abnormality determination threshold value stored in the storage unit 50, and when the deviation difference exceeds the abnormality determination threshold value, the oxygen sensor 11 determines that there is deterioration and outputs an abnormality signal to the alarm unit 70. A determination unit 40 is provided.

Thereby, since it is possible to detect the presence or absence of deterioration of the plurality of oxygen sensors 11, if it is determined that there is deterioration, maintenance can be performed immediately. Further, since the oxygen sensor 11 is superior in response to gas concentration detection in the furnace atmosphere as compared with the CO ₂ sensor, even if the heat treatment furnace 100 is a continuous carburizing furnace, When calculating the CP value, a value closer to real time can be obtained.

1 ... Carbon potential calculation device (CP value calculation device)
DESCRIPTION OF SYMBOLS 10 ... Sensor part 11 ... Oxygen sensor (11a ... 1st oxygen sensor, 11b ... 2nd oxygen sensor)
DESCRIPTION OF SYMBOLS 12 ... Temperature sensor 20 ... Setting part 30 ... Calculation process part 31 ... CP value calculation means 32 ... Deviation difference calculation means 40 ... Determination part 50 ... Memory | storage part 60 ... Display part 70 ... Alarm part 100 ... Heat treatment furnace

Claims (4)

In the carbon potential calculation device for calculating the carbon potential (CP value) of the furnace atmosphere based on the O ₂ concentration, CO concentration, and temperature in the furnace atmosphere detected by a sensor unit installed in the heat treatment furnace,
A sensor unit having two oxygen sensors for detecting the atmosphere in the furnace;
A calculation processing unit that calculates a CP value using a CO concentration that is a preset fixed value and an O ₂ concentration detected by the sensor unit;
A carbon potential calculation device comprising: The calculation processing unit includes deviation difference calculation means for calculating a deviation difference of a voltage value corresponding to the O ₂ concentration detected by each oxygen sensor,
2. The apparatus according to claim 1, further comprising a determination unit that determines that an abnormality is detected and outputs an abnormality signal when the deviation difference calculated by the deviation difference calculation unit exceeds a preset abnormality determination threshold value. The carbon potential calculation apparatus described. The calculation processing unit includes deviation difference calculation means for calculating a deviation difference between CP values calculated according to _two O ₂ concentrations detected by the oxygen sensors,
2. The apparatus according to claim 1, further comprising: a determination unit that determines that an abnormality is detected and outputs an abnormality signal when the deviation difference calculated by the deviation difference calculation unit exceeds a preset abnormality determination threshold value. Carbon potential calculation device. The carbon potential calculation device according to claim 2, further comprising an alarm unit that outputs an alarm to the outside when an abnormal signal is input from the determination unit.

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