JPH0833360B2 - Method for determining crystallization temperature of high temperature melt - Google Patents

Description

The present invention relates to a method for determining the crystallization temperature of a high temperature partition such as powder for continuous casting.

[Prior Art] In general, powder for continuous casting is used not only for the quality of the slab such as surface inclusion defects and cracks in the slab, but also for the progress of solidification of molten steel in the mold, frictional force with the mold It is known that it also has a great influence on the basic factors.In particular, the freezing point temperature, and further the temperature that is an index of crystallization that is a turning point of large viscosity, that is, the crystallization temperature is an important control item. There is.

[Problems to be solved by the invention]

By the way, the freezing point temperature of such a high temperature melt is determined based on the viscosity-temperature measurement data.

However, the conventional viscometer does most of the measurement work manually, and it takes a lot of time for one measurement, and moreover, it is necessary to perform many measurements in a short cycle time when estimating the freezing point temperature. However, it is difficult to obtain sufficient measurement data, and the measured values vary due to the deviation of the measurement timing due to the long measurement time. There is a problem in that sufficient reliability cannot be obtained with respect to the estimated value of the temperature and further the estimated value of the crystallization temperature (the temperature which is an index of crystal precipitation).

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vibrating vibrometer of a vibrating bar method, which requires relatively short measurement work time, among various types of viscometers that have been conventionally proposed. An object of the present invention is to provide a method for determining the crystallization temperature of a high-temperature melt, which enables automation of viscosity measurement work, enables viscosity measurement in a fine cycle, and enables accurate estimation of the crystallization temperature based on these measurement data.

[Means for solving problems]

In the present invention, the high temperature melt is cooled according to a predetermined temperature pattern while maintaining its internal temperature uniform,
After determining the freezing point of the high temperature melt by measuring the viscosity of the high temperature melt and the temperature at that time in the process, the viscosity-temperature characteristic and the freezing point in the molten state of the high temperature melt are determined based on the obtained viscosity-temperature data. The process includes the steps of setting temperature ranges in which the viscosity-temperature characteristics in a region having a higher temperature than that including each obtain substantially linearity, and obtaining the intersections on the extension lines of the viscosity-temperature characteristics for the respective temperature ranges.

[Action]

According to the present invention, the viscosity can be measured many times in a short cycle, and the solidification temperature based on the viscosity-temperature data, and further, the estimated value of the crystallization temperature based on the solidification temperature can be obtained with high reliability.

〔Example〕

Hereinafter, the method of the present invention will be specifically described with reference to the drawings showing an embodiment thereof.

FIG. 1 is a schematic view of an automatic viscosity measuring apparatus used for carrying out the method for determining the crystallization temperature of a high temperature melt according to the present invention, in which 1 is a heating furnace, 2 is a viscosity meter, and 3 is a measuring apparatus body. Shows.

The heating furnace 1 is composed of an electric furnace or the like, has an opening 1a at the center of the upper wall, and has a crucible 11 for containing an object to be measured and a heater 12 for heating and melting the object to be measured. In addition, a feeder 13 for supplying an object to be measured with viscosity to the crucible 11 is installed on the outside of the furnace, and the object to be measured with viscosity inside the supplier 13 is provided in the furnace wall of the heating furnace 1. It is put into the crucible 11 through 1b and heated and melted to a predetermined temperature by the heater 12.

The heater 12 is controlled by the furnace controller 14 which operates based on the control signal from the arithmetic and control unit 31 of the measuring apparatus main body 3, and the result is obtained by the furnace temperature detection probe 15a and the temperature detection probe 15b of the viscosity object to be measured. The detected temperature is fed back to the furnace controller 14 through the multi-thermometer 32 and the arithmetic and control unit 31. Further, the cut-out amount of the viscosity-measured object from the feeder 13 is also adjusted by the arithmetic control unit 31 through the sequencer 33 of the measuring device main body 3.

The viscometer 2 has a shaft 22 having an upper end connected to a vibration source 21 composed of a cone type speaker and the like, hangs down a heat shield plate 23 having a water cooling jacket, and vibrates at the lower end. The vibrating piece 24 is provided with a displacement gauge 25 for detecting the amplitude of the vibrating piece 24 in the vicinity of the upper end of the shaft 22. The position raised outside the
24 is moved up and down through the opening 1a to a position where it is immersed in the viscosity measured object in the crucible 11.

The vibration source 21 is configured to vibrate the vibrating plate by an electric means such as an electromagnet or a drive coil, and transmit the vibration to the vibrating piece 24 through the shaft 22. The frequency and amplitude of the vibrating plate are measured. The calculation control unit 31 of No. 3 sets the vibration source 21 through the oscillator 35 and the power amplifier 36. The resonance frequency of the vibration system is mainly used as the frequency, and the amplitude at that time is also used as the amplitude.

The displacement meter 25 is arranged so as to detect the amplitude of the vibrating piece 24 through the shaft 22, and the detection signal is detected by the controller 26.
Also, it is taken into the arithmetic and control unit 31 through the multimeter 34 of the measuring device body 3.

Reference numeral 16 is a standard viscosity liquid, which is used to determine the characteristics of the viscosity measuring device 2 itself by immersing the vibrating piece 24 therein before starting the viscosity measurement, detecting the temperature and amplitude at that time.

Then, the arithmetic and control unit 31 of the measuring device body 3 outputs a signal for adjusting the cut-out amount of the viscosity-measurable object to the feeder 13 via the sequencer 33 as described above, and also the probe 15 for temperature detection.
The internal temperature of the heating furnace 1 and the temperature of the melted viscosity measured object in the crucible 11 are taken in through a and 15b, and a control signal is sent through the furnace controller 14 to set the temperature of the viscosity measured object to the viscosity measurement temperature. Then, the vibration source 21 is oscillated by a predetermined number of signals via the oscillator 35 and the power amplifier 36, and the amplitude of the vibrating piece 24 in the air at that time, in the viscosity measured object, in the standard viscosity liquid, etc. Is taken in as the detection value of the displacement meter 25, and the viscosity is calculated.

The calculation of the viscosity η by the calculation control unit 31 is based on, for example, the vibration amplitude E of the vibrating piece 24 in the measured object under the resonance frequency detected by the displacement meter 25, according to the following equation (1). Done.

However, [rho: the density of the viscosity measured R _M: resistance of the viscometer inherent mechanical impedance fa: resonance frequency f in the air: the resonance frequency S in the viscosity measured in: area of both surfaces of the vibrating element Note that R _M ² / πfaS ² in the equation (1) is a device constant, and this is K, and Is an attenuation factor, so if this is set to Λ ₀ , the above equation (1) can be rewritten as equation (2).

ρη = KΛ ₀ (2) Resonance frequency fa in air and vibration amplitude Ea in air give vibrations of different frequencies to the vibrating piece in the atmosphere before the start of measurement, and the frequency at which the vibration becomes maximum is the resonance frequency. fa, and the amplitude at that time is defined as Ea. Regarding K and n, before starting the measurement, dip the vibrating piece in two or more kinds of standard viscosity liquids and give the vibrating piece vibrations of different frequencies. The frequency at which the maximum amplitude is f is f, and the amplitude at that time is E And the standard viscosity liquid density ρ, viscosity, etc., are obtained in advance.

The temperature and viscosity of the object to be measured, which are obtained by the arithmetic control unit 31, are displayed and recorded by the CRT and the printer each time.

Next, an example of the procedure for measuring the viscosity will be described according to the temperature patterns shown in FIGS. FIG. 2 is a temperature pattern of the viscosity-measured object, where the horizontal axis represents time and the vertical axis represents temperature.

The setting control of the temperature pattern as shown in FIG. 2 for the viscosity measured object is to detect the temperature directly through the probe 15b inserted into the viscosity measured object in the crucible 11 and to make it follow a predetermined temperature pattern. Although the setting control may be performed from the arithmetic control unit 31 through the furnace controller 14, the temperature response of the viscosity-measurable object is slow, and it takes a long time until the internal temperature becomes uniform. Therefore, normally, the relationship between the object to be measured and the furnace temperature and set time required to set and maintain the object to be measured is obtained in advance and the temperature of the object to be measured is controlled so that it follows a predetermined temperature pattern. It is desirable to set the required furnace temperature control pattern above and to control the furnace temperature accordingly, so that the temperature of the viscosity-measurable object can be made to follow the temperature pattern as shown in FIG. 2, but the following explanation will be given. The temperature pattern of the viscosity measured object shown in FIG.

First of all, after adjusting the equipment and supplying the measured material into the crucible 11 and the feeder 13, the control unit 31 outputs a control signal to the furnace controller 14 to measure the measured material. The temperature of this melt is heated to the highest temperature T _M (or higher temperature) of the temperatures at which viscosity measurement should be performed, and that temperature T _M is kept heated to homogenize the internal temperature. Try. After a certain period of time, the vibrating piece 24 is vibrated at its resonance frequency and the viscosity measuring device 2 is lowered to measure the melt level. Next, the vibration of the vibrating piece 24 in air is measured. The vibrating piece 24 is immersed in the melt to a predetermined depth, and the first viscosity measurement is performed as it is. Perform the second viscosity measurement with a certain time interval while maintaining the viscosity measurement temperature at T _M. After that, measure the viscosity a predetermined number of times while gradually lowering the temperature to the temperature at which the viscosity should be measured. When the temperature is decreased to a temperature T _N that is slightly higher than the predicted freezing point of the viscosity-measuring object, the temperature is continuously decreased with a constant gradient, and then the viscosity is measured in small cycles in a cycle shorter than the previous viscosity measurement cycle. I do When the amplitude of the vibrating piece is attenuated to a predetermined value or less, it is determined that the viscosity measurement target is solidified, and each device is stopped to complete the measurement work.

After that, the viscosity measured object is again heated and melted through the furnace controller 14, the vibrating piece 24 taken in the viscosity measured object is extracted, and the probe 15b for temperature measurement is extracted, and the post-processing is completed. Allow the object to be measured to cool as it is.

 Each work will be specifically described below.

A. Pre-measurement setup work Mainly for inspection of various equipment, supply of viscosity-measurable material into the feeder 13 and the crucible 11, and the like. The supply amount of the viscosity-measurable object into the crucible 11 is determined so that a level at which the viscosity measurement is not hindered in the crucible 11 when melted can be secured.

B ₁ .Measurement of melt level When vibrating the vibrating piece 24 at the resonance frequency and operating the elevating means to lower the vibrating piece 24, the amplitude suddenly changes when the lower end of the vibrating piece 24 comes into contact with the melt surface. The output signal of the displacement meter 25 at that time is read, and the position of the vibrating piece 24 is determined to be the level position based on the position of the elevating means.

Note that this level determination may be calculated based on the amount of the substance to be measured to be put into the crucible 11, the internal volume of the crucible 11, and the density of the substance to be measured.

B ₂ .Amplitude measurement of vibrating piece in air Driving the lifting means of the viscometer 2 to raise the vibrating piece 24 from the estimated position on the surface of the melt to a certain height in the heating furnace 1, and vibrate in air. The amplitude at that time is detected by the displacement meter 25, the detection signal is input to the multimeter 34 via the controller 26, the eddy current is converted into a distance and taken into the arithmetic control unit 31, and the amplitude is stored and the CRT is also stored. Then, it is displayed and recorded through the printer 37.

C _1. Immersion of the vibrating piece, and the first viscosity measurement Determine the descending amount of the vibrating piece 24 from the level of the viscosity measured object in the crucible 11 detected earlier, and place the vibrating piece 24 at the predetermined depth in the melt. Immerse yourself. As soon as the vibrating piece 24 is completely immersed in the melt up to a predetermined position, the first measurement is performed.

That is, the temperature of the melt is detected by the temperature measuring probe 15b, and this is read into the calculation control unit 31 through the multi-thermometer 32, and at the same time, the output of the displacement meter 25 is calculated as the amplitude through the controller 26 and the multimeter 34. The value is read into the control unit 31 and the viscosity is calculated according to the equation (1).

After that, the frequency is changed, the amplitude is read each time, the average amplitude is calculated, and the viscosity is measured.

When the C ₂ .2 nd viscosity measured first as melt temperature even after the viscosity measurement end of a certain time has elapsed while maintaining constant, reads the temperature and amplitude again by repeating the operations described above to obtain the viscosity 2 Perform the second viscosity measurement.

C ₃ ~ C _n .3 ~ _nth viscosity measurement After that, the furnace controller 14 is controlled so as to decrease the furnace temperature at a predetermined gradient, and after a certain time, the furnace controller 14 is controlled again to keep the temperature at that time for a certain time. The temperature of the melt is maintained to be uniform, and the viscosity is measured for the third time.

After that, each time the melt temperature is lowered with a predetermined gradient, the temperature is maintained for a certain period of time repeatedly, and the viscosity is measured n times.

D _{1 to} D _n .Small-scale measurement After the required number of times of viscosity measurement is completed, the viscosity is repeatedly measured in short cycles while lowering the furnace temperature at a predetermined gradient.

The viscosity measuring operation itself is substantially the same as that described above.

E. Freezing point determination Then, when the absolute value of the amplitude value at the resonance frequency of the vibrating piece 24, which is the output of the displacement meter 25, becomes less than or equal to a predetermined set value, the amplitude of the vibrating piece 24 is measured first. The ratio to the amplitude value at the resonance frequency of the resonator element 24 in the air is set value K.
When it becomes lower than that, in other words, when the following expression (3) is satisfied, it is determined that the melt has solidified.

However, K: About 13 to 1/10 F, G. Finishing process After the freezing point is judged, the viscosity measured object is reheated, returned to the molten state, and the vibrating piece 24 and probe 15b taken in this are extracted. The lifting and lowering means pulls up the viscosity measuring device 2 and pulls the vibrating piece 24 out of the furnace.

Next, the procedure of the crystallization temperature determination process based on the viscosity-temperature data obtained by the above-described procedure will be described.

a. Determination of solidification temperature Based on the amplitude measurement value at the resonance frequency in the viscosity-temperature data of the viscosity-measuring object obtained in the above process, or the resonance frequency and the amplitude measurement value at this resonance frequency, the above equation (1) is used. Calculated viscosity η, log η, ρ η, or l
The temperature when ogρη deviates from the preset value K ₁ is defined as the solidification temperature. To show this concretely, the viscosity-temperature data is represented by the reciprocal of the absolute temperature (1 / T) of the object to be measured on the horizontal axis.
3, and the above-mentioned logρη is plotted on the vertical axis, which is as shown in FIG. 3. However, as logη, K ₁ corresponding to K as shown in the equation (3) is given as a set value, and logρη The value on the horizontal axis when the value of exceeds K ₁ is ta ℃ and is the freezing point temperature.

Although 1 / T is shown on the horizontal axis, the temperature t may be used instead of this, and logρη is taken on the vertical axis, but the present invention is not limited to this, and η, logη, ρη described above are substantially taken. Are the same.

b. Determination of viscosity-temperature characteristics during melting In Fig. 4, the reciprocal 1 / T of the absolute temperature T of the viscosity object to be measured is plotted on the horizontal axis and log ρ η on the vertical axis as in the graph shown in Fig. 3. And the freezing point temperature of the melt determined in the a term
Based on ta ° C, the temperature range during which the melt-temperature viscosity-temperature characteristic obtained in the process of lowering the melt temperature from the temperature at which the viscosity was first measured remains approximately linear (as the freezing point approaches, A set temperature Ta ° C is set to specify a range in which the resulting viscosity-temperature characteristic does not include a region having a curved relationship as much as possible, and the viscosity is measured in a temperature range higher than the sum of the freezing point temperature ta + the set temperature Ta. η, logη, ρη, logρ
The relationship between η and the temperature t (° C.) of the viscosity-measurable object or the reciprocal 1 / T of the absolute temperature T of the viscosity-measurable object is linearly approximated using, for example, the least square method, and the viscosity-temperature characteristic at the time of melting ,
The linear equation y = A ₁ x + B ₁ is determined with the horizontal axis as x and the vertical axis as y.

c. Determination of viscosity-temperature characteristics in the temperature range including and including the freezing point temperature. In Fig. 5, the horizontal axis is the reciprocal of the absolute temperature T of the viscosity-measurable object, as in the graphs shown in Figs. 1 / T is also shown by taking logρη on the vertical axis, and includes 1 / T on the basis of the melting point temperature ta ° C of the melt determined in the above item a, and before this.
In other words, the viscosity in the higher temperature range
Set temperature Tb for specifying the temperature range in which the temperature characteristic maintains a substantially linear shape (the range that does not include the region where the viscosity-temperature characteristic that occurs in the higher range of the temperature of the viscosity object to be measured has a curved relationship as much as possible) ℃, the viscosity η, log η, in the temperature range lower than the temperature of the sum of solidification temperature ta + set temperature Tb
The relationship between ρ η, log ρ η and the temperature t (° C.) of the viscosity-measurable object or the reciprocal 1 / T of the absolute temperature T of the viscosity-measurable object is linearly approximated by using, for example, the least square method, and this is included in the freezing point, and The viscosity-temperature characteristic in a temperature range higher than this is defined, and the linear expression y = A ₂ x + B ₂ is determined with x on the horizontal axis and y on the vertical axis.

d. Determination of Crystallization Temperature FIG. 6 is a graph showing the manner of determining the crystallization temperature described above. As with the graphs shown in FIGS. 3 to 5, the horizontal axis represents the reciprocal 1 / absolute temperature of the object to be measured. T is shown, and the vertical axis is logρη. The viscosity of the viscosity-measured object determined in the above item b includes a linear equation y = A ₁ x + B ₁ indicating the viscosity-temperature characteristic and the freezing point temperature of the viscosity-measured object determined in the above item c, and The value t _b of the x coordinate of the intersection Q with the linear equation y = A ₂ x + B ₂ showing the viscosity and temperature characteristics in the high temperature range is taken as the crystallization temperature.

In the above description, the case where the viscosity-temperature characteristics for both temperature ranges are linearly approximated has been described, but it is not always necessary to perform linear approximation, and a curved line may be used as long as the characteristic tendency is not impaired.

 Next, another embodiment of the present invention will be described.

As shown in FIG. 3, the viscosity-temperature characteristic of the viscosity-measurable object includes the freezing point temperature ta ° C., and in the temperature range higher than this and the temperature range in which the viscosity-measurable object is in a molten state, there is a linear relationship. However, it is a method that focuses on the fact that there is a curvilinear relationship in the middle temperature range and that the existence of the crystallization temperature is estimated in the temperature range having this curvilinear relationship. Is performed as follows.

The viscosity-temperature relationship data obtained in the process of lowering the melt temperature of the object to be measured was obtained according to the equation (1) from the amplitude measurement value of the resonator element at the resonance frequency, or the resonance frequency and the amplitude measurement value at the resonance frequency. Viscosity η, log η, ρη, log
The rate of change between two points with the temperature of ρη as the index (temperature change rate differentiated by temperature), that is, the horizontal axis when d (logρη) / d (1 / T) exceeds a preset value by a certain amount or more The value tc ° C. is determined as the crystallization temperature.

Specifically, when the number of times the rate of change d (logρη) / d (1 / T) exceeds the set value is N or more consecutively, and when the N-ith rate of change is obtained. The temperature of tc ° C is defined as the crystallization temperature.

For example, in FIG. 7, the 7th-2nd temperature when the temperature differential value calculated from the two points of log ρη exceeds the set value 7 times or more, that is, the 5th temperature tc is taken as the crystallization temperature. Indicate the case.

The crystallization temperature is used as the crystallization temperature at which the rate of change is determined, and may be appropriately determined according to the material of the viscosity-measuring object.

Further, in the above method, the case where the rate of change between two points of the viscosity-temperature relationship data is obtained has been described, but the present invention is not limited to this, and for example, even if the rate of change at the third point in the middle of five points is obtained. Well in this case d (logρη) /
d (1 / T) is given by the following equation (4).

However h: Viscosity measurement cycle y ₀ ~y _4: The value noted above graph of measurement logρη is has been explained when taking logρη on the vertical axis, eta Alternatively, log [eta, take Roita, also the horizontal axis Instead of the reciprocal 1 / T of the absolute temperature T, t ° C. may be used.

〔effect〕

As described above, in the method of the present invention, the crystallization temperature of the high temperature melt can be more accurately obtained, and a quantitative control index can be obtained with high reliability. The present invention has excellent effects such that higher quality control can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of the device of the present invention, FIG. 2 is a temperature pattern to be set for an object to be viscosity measured, FIGS. 3 to 6 are graphs showing a process of obtaining a crystallization temperature of a high temperature melt, and FIG. 6 is a graph showing another method for obtaining the crystallization temperature in the method of the present invention. 1 ... Heating furnace, 2 ... Viscosity measuring device, 3 ... Measuring device main body, 11 ... Crucible, 12 ... Heater, 13 ... Feeder, 14 ...
… Furnace controller, 15a, 15b …… Temperature detection probe, 1
6 …… Standard viscosity liquid, 21 …… Excitation source, 22 …… Shaft, 24
...... Vibrating element, 25 ...... Displacement meter, 31 ...... Computation control unit

Claims (1)

[Claims] 1. A high temperature melt is cooled according to a predetermined temperature pattern while maintaining its internal temperature uniform, and in the process, the viscosity of the high temperature melt and the temperature at that time are measured to determine the freezing point of the high temperature melt. After the judgment, the temperature at which the viscosity-temperature characteristic in the molten state of the high-temperature melt and the viscosity-temperature characteristic in the higher temperature region including the freezing point based on the obtained viscosity-temperature data are each approximately linear. A method for determining a crystallization temperature of a high temperature melt, which comprises a step of setting a range and obtaining an intersection point on an extension line of a viscosity-temperature characteristic for each temperature range.