JPH0516540B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used to accurately determine the carbon content, silicon content, and carbon equivalent of molten cast iron.
This invention relates to a thermal analysis device that can accurately detect the initial temperature and eutectic temperature from the cooling curve of molten cast iron.

[Conventional technology] Conventionally, the carbon content, silicon content,
As a thermal analysis device for determining carbon equivalent, the correlation between the primary crystal temperature and eutectic temperature obtained from the cooling curves of various molten cast irons and the component elements is determined in advance by multiple regression analysis method, A thermal analysis device is known that determines the component element content and carbon equivalent from the primary crystal temperature and eutectic temperature obtained. but,
Conventional thermal analyzers determine that when the temperature on the cooling curve stagnates within a predetermined temperature range for a predetermined time, the temperature is determined to be the primary crystal temperature or the eutectic temperature. However, in order to improve the detection accuracy of primary crystal temperature and eutectic temperature in devices using this method, it is necessary to make the set temperature range as narrow as possible. Unless the conditions are shortened, the stagnation point cannot be detected.
Therefore, it has not yet been possible to detect the primary eutectic temperature with sufficient accuracy.

[Problems to be Solved by the Invention] The present invention has been made to improve these conventional drawbacks, and is an object of the present invention to detect the primary crystal temperature and eutectic temperature of molten cast iron at high speed and with high precision. The purpose is to

[Means and effects for solving the problems] FIG. 1 is a block diagram showing the concept of the present invention.

The thermal analysis device for molten cast iron of the present invention includes a temperature measuring device 10 that measures the temperature of the molten metal in time series during the cooling process, and a temperature measuring device 10 that inputs signals from the temperature measuring device, analyzes the data, and performs predetermined processing. A data analysis device 20 that outputs a signal to an output device, and an output device 30 that receives a signal from the data analysis device and displays the signal based on the signal, the data analysis device 20 includes: a primary crystal temperature range determination unit 21 that detects that the temperature data output from the temperature measuring device is within a preset primary crystal temperature existence range; a eutectic temperature range determination unit 22 that detects that the temperature is within the existing range; a stagnation area detection unit 23 that detects a period between the current value and the previous time as a stagnation area of temperature; and a stagnation area detected by the primary temperature range determination unit, where the stagnation area is a plurality of temperature stagnation areas. The section detected by the primary crystal temperature detection section 24 which takes the representative temperature in the continuous stagnation section as the primary crystal temperature when it occurs continuously over the sampling period, and the eutectic temperature range judgment section. a second temperature decrease in which the stagnation zone occurs continuously over a plurality of sampling periods, and the temperature gradient between two sampling points within the continuous stagnation zone is smaller than the first temperature decrease rate; and a eutectic temperature detection section 25 which determines the representative temperature between the two sampling times as the eutectic temperature when the temperature is less than or equal to the eutectic temperature.

The primary crystal temperature range determining unit 21 sets in advance upper and lower temperature ranges in which primary crystal temperatures measured for a large number of samples exist, and determines that the measured temperature data is within the set primary crystal temperature range. judge. In addition, the eutectic temperature range determining unit 22 similarly sets the upper and lower limits of the temperature at which the eutectic temperature can exist, and determines whether or not the measured data exists within this eutectic temperature range. .

In the cooling curve of molten cast iron, what characterizes the primary crystal temperature and the eutectic temperature is the rate of change in temperature in the cooling curve. That is, the primary crystal temperature or eutectic temperature is
It exists in a range where the temperature gradient of the cooling curve is small due to the physicochemical properties of the crystal. In the present invention, when the temperature gradient at any temperature data point is within a range smaller than a predetermined first temperature decrease rate, the range where that temperature point exists is detected as a stagnation area.

The primary crystal temperature is within the temperature range detected by the primary crystal temperature range determination section, and when the stagnation section detected by the stagnation section detection section occurs for a predetermined number of consecutive samples, the representative of the stagnation section is determined. Represented by points. As this representative point, the temperature at the beginning or end of the stagnation section, or the average value of the temperatures may be used.

The detection of the eutectic temperature is performed in an area detected by the eutectic temperature range determination unit, within which there is a stagnation area detected by the stagnation area detection unit,
When the length of the stagnation section is greater than or equal to a plurality of sampling numbers, and the temperature gradient between two points separated by a predetermined number of samples in the stagnation section is equal to or less than a second temperature reduction rate that is smaller than the first temperature reduction rate,
The temperature at the representative point between the two points is defined as the eutectic temperature. In this way, the eutectic temperature is detected not only by the stagnation section determined by the differential slope method, but also by determining when the slope of the macroscopic curve in the stagnation section is less than a predetermined value. The temperature at a representative point in the stagnation section where the rate of temperature decrease is less than or equal to the second temperature decrease rate within the continuous stagnation section is defined as the eutectic temperature. As the representative point of the section, for example, one of the two points or a point that gives the average value of the temperatures of the two points is selected.

[Examples] Hereinafter, the present invention will be described in detail based on specific examples. FIG. 2 is a block diagram showing the configuration of a measuring device according to a specific embodiment of the present invention. 2 is a cup for taking out a portion of the molten metal and measuring its cooling curve. A thermocouple 4 made of alumel-chromel is provided at the bottom of the cup 2, and the power generated by the thermocouple 4 is inputted to a thermometer 6 via a conductor. The thermometer 6 samples the analog electromotive force every 0.4 seconds, converts it into a digital signal, and outputs it to the parallel/serial converter as an encoded code expressed in binary coded decimal (BCD). The parallel/serial converter 8 converts the BCD data into serial data and outputs it to the serial data input port of the microcomputer 10. A printer 12 and a CRT 16 for outputting predetermined measurement results are connected to the microcomputer 10, and a floppy disk device 14 storing a predetermined program is connected thereto.

FIG. 3 is a flowchart showing the processing steps of the microcomputer 10 used in the apparatus of the present invention. Step 100 is a step for setting initial values of various parameters. In step 102, the axes of a graph for displaying the temperature data measured on the CRT 16 are displayed. step
At 104, temperature data is read from the thermometer 6. When the measured temperature data reaches a predetermined temperature or higher in step 106, it is assumed that molten metal has been poured into the cup 2, and measurement is started. If the temperature is below the predetermined temperature, the process returns to step 104 since molten metal has not yet been poured into the cup 2.

At step 108, the parameter I that stores the sampling number of the measurement data is updated by 1. step
Read temperature data at 110. Next, in step 112, it is determined whether the measurement of the cooling curve has been completed. The conditions for determining the end of the measurement of the cooling curve are that the number of measurements is greater than or equal to a predetermined number of times, or that the measured temperature is less than or equal to a predetermined temperature. The temperature data measured in step 114 is displayed on the CRT 16. That is, temperature data is measured and displayed on the CRT 16 in real time. Next, in step 116, the maximum temperature of the cooling curve is detected. The cooling curve shows that after pouring into cup 2, the temperature rises rapidly to the maximum temperature, and then the cooling process continues. Therefore, by detecting the temperature change,
Maximum temperature can be detected. step 118
If the maximum temperature is not detected in step 108
Go back and repeat the cycle. If the maximum temperature is detected, the process moves to step 120.

In step 120, the temperature difference ΔT between the two points is determined.
Next, the process moves to step 122, where it is determined whether the detection of the primary crystal temperature has been completed, and if not, the process proceeds to step 122.
Move to 124. In step 124, the range in which the primary crystal temperature exists is determined. The judgment condition is the following equation.

2070〓<T<2300〓 If the measured temperature T is within the primary crystal temperature range, the process moves to step 140.

Steps 140, 142, and 144 correspond to a stagnation section detection section that detects stagnation sections. ΔT at step 140
is smaller than 1, that is, the temperature gradient is ±2.5〓/
sec range (range below the first temperature decrease rate in the present invention), it is defined as a stagnation zone.
That is, in step 142, the number of sampling points in the stagnation section is counted to detect the stagnation section. If the above conditions are not met, a register for counting sampling points is reset in step 144 in preparation for the detection of the next stall interval.

Steps 144 and 146 correspond to a primary crystal temperature detection section which determines the primary crystal temperature when the number of stagnation points in the stagnation section detected by the stagnation section detection section is seven or more.
If the number of stagnation points is 7 or more in step 146,
The average temperature in that section is detected as the primary crystal temperature TL.

In step 148, the primary crystal temperature TL is displayed on the CRT. The primary crystal temperature was detected through the above processing steps.

Next, the process of detecting the eutectic temperature will be described. Next, cooling progresses further and in step 128, if the measured temperature data exists within the eutectic temperature range,
Move to step 170. The determination conditions of this eutectic temperature range determination section are as follows.

2028〓<T<2070〓 Steps 170, 172, and 174 are stagnation section detection units having the same functions as those described above.

Steps 176, 178, and 180 proceed to step 178 if the number of stagnation points existing in the stagnation section is 20 or more in step 176, which is the eutectic temperature detection section, that is, if the stagnation time is 8 seconds or more. In step 178,
It is determined whether the temperature difference between two points separated by two sampling numbers is 1〓 or less (lower than the second temperature decrease rate in the present invention), and when the condition is met, the step
At 180, the temperature at the later sampling point is detected as the eutectic temperature. Then, in step 182, the eutectic temperature TE is displayed on the CRT.

Through the above steps, if the cooling curve is typical, the primary crystal temperature TL and the eutectic temperature TE are detected, and it is determined in step 112 that the measurement is complete.

On the other hand, if the cooling curve is not typical, for example if no primary crystal temperature is detected in step 126, then parameter A is set to 1 in step 127. Also, if the primary crystal temperature is detected but the eutectic temperature is not detected, the step
At 130, parameter A is set to 2.

When the cooling curve measurement is completed, proceed to the step
Move to 190. If the parameter A is 0, this means that the primary crystal temperature and the eutectic temperature have been detected, and the process moves to step 206 to calculate the silicon content, carbon content, and carbon equivalent, and calculate these values. Display in 208. Further, in step 210, the cooling curve, primary crystal temperature, eutectic temperature, carbon content, silicon content, carbon equivalent, etc. are output to the plotter. The output diagram is shown in FIG.

On the other hand, if it is determined in step 192 that parameter A is 1, the process moves to step 194.
That is, this is a case where the primary crystal temperature is not detected. In this case, in step 194, trace back from the final measurement point to the highest temperature, find the longest stagnation section within that range, and find the number of stagnation points in that stagnation section.
The conditions for determining this stagnation section are the same as the conditions for the stagnation section detection section described above. If the number of stagnation points is 27 or more at step 196, move to step 198,
Let the representative point of the stagnation zone be the eutectic temperature. Next, proceed to step 200 to further find the longest stagnation interval between the maximum temperature and the eutectic temperature just found.
Find the number of stagnation points that exist in that stagnation section. If the number of stagnation points is 5 or more in step 202, the process moves to step 204 to obtain the primary crystal temperature TL. In this way, when the primary crystal temperature and the eutectic temperature are not detected under the above-mentioned primary crystal determination conditions and eutectic determination conditions, the eutectic temperature and the primary crystal temperature are determined using another, somewhat relaxed, determination condition. Detected.

Also, if the value of A is 2 in step 220,
This is a case where the primary crystal temperature is detected but the eutectic temperature is not detected. In that case, proceed to step 222.
The same processing as step 194 is performed. step
224 and the number of stagnation points is 27 or more, step 226
The average temperature in the stagnation zone is detected as the eutectic temperature. In this way, in this embodiment, in addition to the detection method using the device of the present invention, a detection method based on other conditions is added to ensure the detection of primary crystal and eutectic temperatures.

[Effects of the Invention] According to the present invention, when the temperature gradient between two adjacent points on a cooling curve is below a predetermined range, that range is defined as a temperature stagnation zone. Furthermore, the range in which the primary crystal temperature exists and the range in which the eutectic temperature exists are set in advance. The stagnation time, which is one of the conditions for determining primary crystals and eutectics, is different. Further, the eutectic temperature is determined only when a stagnation area where the temperature reduction rate is smaller than the first temperature reduction rate continuously appears for multiple sampling periods, and a second temperature smaller than the first temperature reduction rate within this stagnation area. Since the representative temperature within the stagnation zone where the temperature decrease rate below the decrease rate appears is detected as the eutectic temperature, even if the difference between the current value and the previous value in a certain sampling period is smaller than the second temperature decrease rate due to some disturbance. Even so, the probability that multiple sampling periods before and after this sampling period will continue to have a temperature reduction rate equal to or lower than the first temperature reduction rate is small, so it is possible to eliminate such measurement errors. The eutectic temperature can be detected with high accuracy. By using such conditions, the primary crystal temperature and eutectic temperature could be detected with high accuracy. Moreover, the device of the present invention has the following features:
Since the above detection is automated, primary crystal and eutectic temperatures can be detected reliably and quickly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the concept of the apparatus of the present invention. Figure 2 shows a specific example of the present invention.
1 is a block diagram showing the configuration of a thermal analysis device according to an example. FIGS. 3 and 4 are flowcharts showing the processing of the microcomputer used in the apparatus of the same embodiment. FIG. 5 is an output diagram of the apparatus of this embodiment.

Claims (1)

[Scope of Claims] 1. A temperature measuring device that measures the temperature in the cooling process of molten metal in time series; A signal from the temperature measuring device is input, the data is analyzed, and after predetermined processing, the data is output to an output device. A data analysis device that outputs a signal; and an output device that inputs a signal from the data analysis device and displays the signal based on the signal, the data analysis device comprising: a data analysis device that outputs a signal from the temperature measurement device; a primary crystal temperature range determining unit that detects that the temperature data is within a preset primary crystal temperature range; and a unit that detects that the temperature data is within a preset eutectic temperature range. a crystal temperature range determination unit; and when the difference between the current value and the previous time of temperature data input every predetermined sampling period is less than or equal to a predetermined first temperature reduction rate, the difference between the current value and the previous time is determined. a stagnation area detection unit that detects the period as a temperature stagnation area; and a stagnation area detected by the primary temperature range determination unit, where the stagnation area occurs continuously over a plurality of sampling periods. a primary crystal temperature detection section that takes a representative temperature within the continuous stagnation section as the primary crystal temperature; and an section detected by the eutectic temperature range determination section, where the stagnation section falls into a plurality of sampling periods. between the two sampling time points when the temperature gradient between the two sampling time points within the continuous stagnation interval is equal to or less than a second temperature reduction rate that is smaller than the first temperature reduction rate; A thermal analysis device for molten cast iron, comprising a eutectic temperature detection section whose representative temperature is a eutectic temperature.