CN113740374A - Device and method for measuring crystallization starting temperature of high-temperature slag based on conductivity - Google Patents

Device and method for measuring crystallization starting temperature of high-temperature slag based on conductivity Download PDF

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CN113740374A
CN113740374A CN202111142814.5A CN202111142814A CN113740374A CN 113740374 A CN113740374 A CN 113740374A CN 202111142814 A CN202111142814 A CN 202111142814A CN 113740374 A CN113740374 A CN 113740374A
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temperature
slag
conductivity
measuring
molybdenum rod
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张晨
吴婷
雷杰
王海川
鲍光达
廖直友
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Anhui University of Technology AHUT
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Anhui University of Technology AHUT
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/14—Investigating or analyzing materials by the use of thermal means by using distillation, extraction, sublimation, condensation, freezing, or crystallisation
    • G01N25/147—Investigating or analyzing materials by the use of thermal means by using distillation, extraction, sublimation, condensation, freezing, or crystallisation by cristallisation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance

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Abstract

The invention discloses a device and a method for measuring crystallization starting temperature of high-temperature molten slag based on conductivity, and belongs to the technical field of metallurgical molten slag performance detection. The device mainly comprises a conductivity test system, a heating system, a lifting system, an atmosphere control system and a temperature control system, is used for measuring the crystallization starting temperature of the high-temperature slag, and particularly records the conductivity value in the continuous cooling process of the slag in real time by using a precise LCR digital bridge and a molybdenum rod and adopting a four-probe method, thereby finally determining the crystallization starting temperature of the slag. By adopting the technical scheme of the invention, the temperature in the furnace, the bottom end of the molybdenum rod and the depth of the molybdenum rod inserted into the high-temperature slag can be accurately controlled, the influences of the resistance of the molybdenum rod and a lead and the polarization effect in the high-temperature slag are eliminated, and the conductivity value in the slag cooling process is accurately measured, so that the crystallization starting temperature of the slag is obtained based on the conductivity-temperature curve.

Description

Device and method for measuring crystallization starting temperature of high-temperature slag based on conductivity
Technical Field
The invention belongs to the technical field of metallurgical slag performance detection, and particularly relates to a device and a method for measuring the crystallization starting temperature of slag based on conductivity.
Background
In the steel smelting process, slag plays the important roles of separating or absorbing impurities, protecting metal from environmental pollution, reducing metal heat loss and the like, so the steel industry has the general consensus that 'steel making is performed in slag making, and good steel is produced under good slag'. The covering slag is used as a functional material for guaranteeing the smooth continuous casting production and the excellent casting blank quality, has the most strict and harsh performance requirements, and is required to be in compliance with the continuous updating of steel variety research and development and the continuous improvement of quality requirements. Adding the casting powder on the liquid level of the crystallizer, melting the casting powder, flowing into a gap between a casting blank and the wall of the crystallizer, solidifying the casting powder by the side of the wall of the crystallizer to form a solid slag film, and controlling the transverse heat transfer in the crystallizer by the thickness and the heat transfer coefficient of the solid slag film; the liquid slag film is formed on one side of the blank shell, and the lubrication of the casting blank is controlled by the thickness of the liquid slag film, so that the heat transfer and lubrication actions of the covering slag in the slag channel directly determine the smooth continuous casting production, and the crystallization characteristic of the covering slag is an important performance parameter influencing the lubrication and heat transfer actions of the covering slag.
The accurate measurement of the initial crystallization temperature of the mold flux is an important guarantee for the development and application of the mold flux. At present, the determination method of the crystallization temperature of the casting powder comprises a hot wire method, a parallax scanning calorimetry method, a high-temperature laser confocal microscope, an electric conduction method, a capacitance method, a viscosity-temperature curve method and the like. The hot wire method and the parallax scanning calorimetry method use 5-10 mg of samples during testing, and if the casting powder contains volatile components, the testing result is seriously influenced. The high-temperature confocal method has high equipment cost and complicated test process. The conductivity method proposed in the chinese patent "a measuring apparatus and method for crystallizer covering slag crystallization temperature" (application No. 201110077464.9, application date is 2011, 3, 29), because direct current is used in the test, there is a serious polarization effect, which affects the accuracy of the test result, and in addition, the data fluctuation is large from the test result, which is not stable enough. The capacitance method is to utilize the liquid capacitance ratio of the covering slagThe solid capacitance is higher by several orders of magnitude, so that the crystallization temperature of the slag can be measured, and only the crystallization temperature can be obtained, but the structural information of the slag cannot be obtained at the same time. The viscosity-temperature curve method is that the viscosity increases faster when the temperature is lower than a certain temperature, namely the turning point temperature TbrMany scholars believe that the turning temperature is related to slag crystallization, but there is no uniform argument. Meanwhile, in the viscosity-temperature curve testing process, when the viscosity is lower than the turning temperature, the viscosity of the covering slag is greatly increased and easily exceeds the range of the viscosimeter, so that the testing process is concerned at any moment, when the viscosity is higher than a certain specific value, the rotation of the measuring head is stopped immediately so as to avoid damaging a rotating shaft of the viscosimeter, the operation is complicated, and the risk of equipment loss exists because the viscosity-temperature curve is adopted to test the turning temperature of the covering slag. Therefore, there is a need for a device that is easy and convenient to operate, low in cost, and stable and reliable in measurement data, and is used for accurately measuring the crystallization starting temperature of the mold flux.
Disclosure of Invention
1. Problems to be solved
The invention aims to overcome the defects of relatively poor accuracy and stability of measured data, complex operation, large equipment loss and high cost in the prior art when the crystallization temperature of the covering slag is measured, and provides a device and a method for measuring the crystallization starting temperature of high-temperature slag based on conductivity. The technical scheme of the invention can effectively solve the problems, the conductivity value in the slag cooling process is accurately measured, the crystallization starting temperature of the slag is obtained based on the conductivity-temperature curve, the measuring process is simple and convenient, the error is small, and the cost is lower.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the invention discloses a device for measuring the crystallization starting temperature of high-temperature slag based on conductivity, which comprises a conductivity measuring system, a lifting system, a heating system and a temperature control system, wherein:
the conductivity measuring system is used for measuring the conductivity of standard liquid or high-temperature molten slag and comprises a precise LCR digital bridge, a corundum sleeve and a molybdenum rod, wherein the molybdenum rod is used as a probe and sleeved in the corundum sleeve, and the top of the molybdenum rod is connected with the precise LCR digital bridge through a lead when the molybdenum rod is used;
the lifting system is used for controlling the lifting of the molybdenum rod;
the heating system comprises a heating furnace, a silicon-molybdenum rod and a crucible, wherein the crucible and the silicon-molybdenum rod are positioned in the heating furnace, and high-temperature slag to be detected is filled in the crucible (3-1) and is used for heating the high-temperature slag to be detected;
the temperature control system comprises a thermocouple and an electrical control cabinet, the thermocouple is arranged on the periphery of the crucible, the data output end of the thermocouple is connected with the electrical control cabinet and used for inputting the measured temperature signal into the electrical control cabinet, and the electrical control cabinet controls the heating temperature according to the received temperature signal.
Furthermore, the device also comprises an atmosphere control system, wherein the atmosphere control system adopts an Ar gas cylinder and is used for protecting the molybdenum rod.
Furthermore, the conductivity measuring system also comprises a positioning plate, a same-diameter parallel clamp and a limiting ring, wherein the positioning plate is connected with the lifting system, and the same-diameter parallel clamp is fixed on the positioning plate and used for fixing the corundum sleeve; the molybdenum rod is sleeved in the corundum sleeve through the limiting ring.
Furthermore, the lifting system comprises a mounting frame and a lifting rod, and the mounting frame is respectively connected with the positioning plate and the lifting rod in an installing mode.
Furthermore, the lifting system further comprises a lifting rod driving piece, a displacement sensor and a controller, wherein the signal output end of the displacement sensor is connected with the displacement signal input end of the controller, the displacement signal output end of the controller is connected with the lifting rod driving piece, and the lifting rod driving piece is used for controlling the lifting rod to lift.
Furthermore, the thermocouple comprises a bottom thermocouple and a side thermocouple, and the bottom thermocouple is arranged at the bottom of the crucible and is used for collecting temperature data of the bottom of the crucible; the side thermocouple is arranged on the side wall of the crucible and used for collecting temperature data of the side wall of the crucible; a thermocouple mounting hole, a heating body lead inlet and a gas inlet are formed in the wall of the heating furnace, and the thermocouple is mounted on the wall of the furnace through the thermocouple mounting hole.
The invention discloses a method for measuring the crystallization starting temperature of high-temperature slag based on conductivity, which adopts the device for measurement and specifically comprises the following steps:
measuring the total impedance of standard liquid with known conductivity by using the device by adopting a four-probe method, and calculating to obtain a conductivity cell constant C;
secondly, introducing dry high-purity argon into a furnace tube of the heating furnace;
step three, preparing high-temperature slag to be detected, placing the high-temperature slag in a crucible for heating, controlling the high-temperature slag to be detected to be molten and then placing the crucible on a base of a heating furnace when the height of the slag is 20-28 mm, heating the high-temperature slag in the crucible to a required temperature, and connecting four molybdenum rods with a lead of a precise LCR digital bridge after the high-temperature slag is uniformly molten;
fourthly, controlling the molybdenum rod to descend by adopting the lifting system so that the molybdenum rod reaches the surface of the high-temperature molten slag;
step five, continuously controlling the molybdenum rod to descend to 9mm below the liquid level of the high-temperature molten slag, adjusting the frequency of the excitation voltage, measuring the impedance of the high-temperature molten slag, and calculating the conductivity of the high-temperature molten slag;
step six, setting a proper cooling speed, measuring the impedance of the high-temperature slag in the continuous cooling stage, and calculating the total conductivity of the high-temperature slag according to the conductivity cell constant C obtained in the step one;
and step seven, drawing a continuous conductivity-temperature curve of the high-temperature slag according to the conductivity and temperature data of the multiple groups of high-temperature slag obtained in the step six, and calculating to obtain the crystallization starting temperature of the high-temperature slag.
Furthermore, in the fourth step, the descending speed of the molybdenum rod is controlled to be 3.7 mm/s; controlling the frequency of the excitation voltage to be 2 kHz-6 kHz, and taking the minimum value of the measured impedance as the impedance of the high-temperature slag; and step six, a temperature control system is arranged to control the cooling speed, and the calculation formula of the electric conductivity of the high-temperature slag is k ═ C/R.
Furthermore, in the seventh step, the method for calculating the crystallization starting temperature according to the conductivity-temperature curve of the high-temperature slag comprises the following steps: and drawing tangent lines of curves in different temperature stages by taking 10000/T as an abscissa and ln (k) as an ordinate, and finding out the temperature corresponding to the change of the conductivity along with the temperature change rate through the intersection of the tangent lines, namely the crystallization starting temperature of the slag.
Furthermore, in the step one, a KCl solution is used as a standard solution, and the method for determining the conductivity cell constant C specifically comprises the following steps:
putting a beaker filled with a KCl solution with the concentration of 1mol/L into a constant-temperature water bath kettle, and keeping the temperature of the KCl solution constant at 35 ℃; connecting a lead of the precise LCR digital bridge to the molybdenum rod, slowly descending the molybdenum rod, and when the impedance value on the precise LCR digital bridge is suddenly changed from a few Komegas or a few Momegas to a few omegas, indicating that the molybdenum rod reaches the surface of the solution; then continuing to descend the molybdenum rod to the liquid level below 9mm, adjusting the frequency of the excitation voltage to be 50 kHz-60 kHz, when the measured impedance is the minimum value, the impedance is the total impedance of the KCl solution, and the conductivity k of the KCl solution at 35 ℃ is 1mol/L due to the electric conductivity k of the KCl solution at 35 DEG CKClKnown as kKCll0.1311S/cm is taken to obtain the conductance cell constant C ═ RKCl×kKClWherein R isKClThe impedance of the resulting KCl solution was measured.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the device for measuring the crystallization starting temperature of the high-temperature slag based on the conductivity, the whole structure and the composition of the device are optimally designed, particularly, a precise LCR digital bridge, a molybdenum rod and a corundum sleeve are selected for a conductivity measurement system, the liquid level position of the high-temperature slag can be accurately measured, the accuracy and the stability of a subsequent measurement result can be effectively guaranteed, the operation is simple, the equipment requirement is lower, and the cost is low.
(2) According to the device for measuring the crystallization starting temperature of the high-temperature slag based on the conductivity, the corundum sleeves and the molybdenum rods are fixed by the fixing plates, the positioning rings and the parallel clamps with the same diameter, and the distance between the molybdenum rods is controlled by the parallel clamps with the same diameter, so that the installation and the replacement of each corundum sleeve and each molybdenum rod are facilitated, and the levelness and the distance of the bottom ends of the molybdenum rods can be accurately controlled.
(3) According to the device for measuring the crystallization starting temperature of the high-temperature slag based on the conductivity, the temperature control system is arranged, the composition of the temperature control system is optimally designed, the temperature in the furnace can be accurately controlled, the influence of the resistance of a molybdenum rod and a lead and the polarization effect in the high-temperature slag is eliminated, the measurement error is effectively reduced, and the device is simple and convenient to operate and high in automation degree.
(4) The device for measuring the crystallization starting temperature of the high-temperature slag based on the conductivity can continuously and accurately measure the conductivity change of the high-temperature slag in the cooling process, and obtains the crystallization starting temperature of the slag based on the conductivity-temperature curve, thereby providing an important theoretical support for the performance detection and analysis of the slag.
(5) The method for measuring the crystallization starting temperature of the high-temperature slag based on the conductivity is used for measuring, and the conductivity of the high-temperature slag can be accurately measured by optimizing and controlling the measuring steps.
Drawings
FIG. 1 is a schematic two-dimensional structure diagram of a device for measuring the electrical conductivity of high-temperature molten slag according to the present invention;
FIG. 2 is an enlarged schematic view of detail A of FIG. 1;
FIG. 3 is an enlarged schematic view of detail B of FIG. 1;
fig. 4 is a graph showing a conductivity-temperature curve of mold flux measured using the apparatus of the present invention and a viscosity-temperature curve measured using a Brookfield viscometer.
In the figure:
1. a bottom thermocouple; 2. a base; 3-1, a crucible; 3-2, molybdenum rods; 3-3, a furnace tube; 3-4, corundum sleeve; 4. a side thermocouple; 5. a silicon-molybdenum rod; 6. a furnace wall; 7. a furnace cover; 8. a lifting rod; 9. a mounting frame; 10. positioning a plate; 11-1, parallel clamps with the same diameter; 11-2, a limit ring; 12. a precision LCR digital bridge; 13. an electrical control cabinet; 14. and an Ar gas cylinder.
Detailed Description
Currently, for the measurement of the temperature at which the mold flux starts to crystallize, the conventional method has the defects recorded in the background art, and particularly, the accuracy and stability of the measured data are poor. The invention provides a device and a method for measuring the crystallization starting temperature of high-temperature slag based on conductivity, which can better solve the defects. The conductivity can represent the total amount of charged particles in the solution, and because the ionic nature of the molten slag at high temperature is based on an electrochemical principle, the conductivity of the molten slag and the diffusion of ions in the molten slag have important influence on the reactivity of the steel slag and the performance of the molten slag, the molten slag conductivity test technology is developed and applied to a certain extent. Since the conductivity changes along with the temperature reduction in the conductivity test process, a slag conductivity-temperature curve can be obtained. When the slag is crystallized, the electric conductivity is suddenly changed, and the initial crystallization temperature of the slag can be obtained by measuring the electric conductivity. In addition, in the process of measuring the conductivity, the probe in contact with the molten slag cannot be damaged due to the solidification of the molten slag, so that the technical scheme of the invention can realize the synchronous measurement of the conductivity and the crystallization starting temperature, and has stable and reliable data, more convenience and safety and lower cost.
Specifically, the device comprises a conductivity measurement system, a lifting system, a heating system, an atmosphere control system, a temperature control system and a display system, wherein the conductivity measurement system is used for measuring the conductivity of the standard liquid or the high-temperature molten slag, and the lifting system is used for controlling the lifting of measurement equipment in the conductivity measurement system. The heating system is used for heating the high-temperature slag. The temperature control system controls the heating temperature, and the atmosphere control system is used for protecting the measuring equipment in the conductivity measuring system and preventing the measuring equipment from being oxidized. The display system may employ a display screen for displaying the measurement data and the measurement profile. According to the invention, the overall structure and the composition of the device are optimally designed, so that the liquid level position of the high-temperature molten slag can be accurately measured, the accuracy and the stability of subsequent measurement results can be effectively ensured, the operation is simple, the equipment requirement is lower, and the cost is low.
Specifically, as shown in fig. 1-3, the conductivity measurement system includes a precision LCR digital bridge 12, a corundum sleeve 3-4, a molybdenum rod 3-2, a positioning plate 10, a parallel clamp 11-1 with the same diameter, and a limiting ring 11-2. The molybdenum rod 3-2 is used as a probe and sleeved in the corundum sleeve 3-4, and the top of the molybdenum rod is connected with the precise LCR digital bridge 12 through a conducting wire when the corundum sleeve is used. The same-diameter parallel clamp 11-1 is fixed on the positioning plate 10, the corundum sleeve 3-4 is fixed on the same-diameter parallel clamp 11-1, the distance between the corundum sleeves 3-4 is adjusted through the same-diameter parallel clamp 11-1, the molybdenum rod 3-2 penetrates into a hole of the corundum sleeve 3-4, and the molybdenum rod 3-2 is fixed in the corundum sleeve 3-4 through the limiting ring 11-2.
The lifting system comprises a mounting rack 9, a lifting rod 8, a lifting rod driving piece, a displacement sensor and a controller, wherein the mounting rack 9 is respectively connected with a positioning plate 10 and the lifting rod 8 in an installing mode. The signal output end of the displacement sensor is connected with the displacement signal input end of the controller, and the displacement control signal output end of the controller is connected with the lifting rod driving piece to control the lifting rod driving piece to lift and work. The installation and adjustment processes of the molybdenum rod 3-2 are that the bottom end of the molybdenum rod 3-2 touches the flat upper surface of the heating furnace body which is horizontally placed by adjusting the height of the lifting rod 8, the limiting ring 11-2 is taken down, the lifting rod 8 is adjusted again, the molybdenum rod 3-2 is exposed out of the corundum sleeve by 35mm, the limiting ring 11-2 is reinstalled, and the molybdenum rod 3-2 is fixed in the corundum sleeve 3-4. By arranging the lifting rod driving piece, the displacement sensor and the controller, the lifting of the molybdenum rod 3-2 can be automatically controlled conveniently, and the operation is convenient.
The heating system comprises a heating furnace, a silicon-molybdenum rod 5 and a crucible 3-1, wherein the heating furnace comprises a furnace wall 6, a connecting pipe, a base, a furnace tube and a furnace cover 7. The furnace cover 7 is arranged above the furnace tubes 3-3, and the furnace wall 6 is provided with a thermocouple mounting hole, a heating body lead inlet and a gas inlet. The crucible 3-1 and the silicon-molybdenum rod 5 are positioned in a heating furnace, and the crucible 3-1 is filled with standard liquid or high-temperature slag for heating the standard liquid or the high-temperature slag. The atmosphere control system adopts an Ar gas cylinder 14, when the to-be-measured slag in the crucible 3-1 is heated, dry high-purity argon in the Ar gas cylinder 14 is introduced into the furnace tube 3-3, and the molybdenum rod 3-2 is prevented from being oxidized, so that the molybdenum rod 3-2 is protected, and the measurement accuracy is improved.
The temperature control system comprises a thermocouple and an electrical control cabinet 13, the thermocouple is arranged on the periphery of the crucible 3-1 and is arranged on the furnace wall 6 through a thermocouple mounting hole, the thermocouple mainly comprises a bottom thermocouple 1 and a side thermocouple 4, and the bottom thermocouple 1 is arranged at the bottom of the crucible 3-1 and is used for collecting temperature data of the bottom of the crucible 3-1; the side thermocouple 4 is arranged on the side wall of the crucible 3-1 and used for collecting temperature data of the side wall of the crucible 3-1. Meanwhile, the data output ends of the bottom thermocouple 1 and the side thermocouple 4 are connected with an electrical control cabinet 13 and used for inputting measured temperature signals into the electrical control cabinet 13, and the electrical control cabinet 13 controls the heating temperature of the high-temperature slag in the crucible 3-1 according to the received temperature signals.
The measuring method of the invention adopts the device to measure, and comprises the following steps: and step one, measuring the total impedance of the standard solution with known conductivity by using the device by adopting a four-probe method, and calculating to obtain a conductivity cell constant C.
The relation between the conductor resistance and the conductivity is R ═ 1/k (L/A), wherein R is the conductor impedance; k is the conductor conductivity; l is the length of the conductor; a is the cross-sectional area of the conductor. The electrical conductivity of the high-temperature slag is measured in a conductivity cell, and since the length and the sectional area of the conductive melt are difficult to determine, L/a is taken as a whole to be a conductivity cell constant, which is denoted as C, and C is R × k. The conductivity cell constant is independent of the properties of the conductive melt, is determined only by the size of the conductive melt, and can be calibrated by taking a KCl aqueous solution with known conductivity as a standard solution. The specific measurement method is as follows:
first, 40ml of a 1mol/L KCl solution was prepared using a 100ml beaker, and the beaker containing the KCl solution was placed in a thermostatic waterbath so that the temperature of the KCl aqueous solution was kept constant at 35 ℃. Then, fixing the tops of four corundum sleeves 3-4 by adopting parallel clamps 11-1 with the same diameter, placing the corundum sleeves in the aperture of the positioning plate 10, and placing four probes (namely molybdenum rods 3-2) into the corundum sleeves 3-4And the bottom end is arranged on the flat upper surface of the heating furnace body which is horizontally arranged. The four probes are exposed out of the corundum sleeve by 35mm by adjusting the lifting rod 8, and the upper part of the molybdenum rod 3-2 is fixed by the limiting ring 11-2 and is fixed in the corundum sleeve 3-2. The wires of the precision LCR digital bridge 12 are then connected to four probes. In order to prevent the corundum sleeve 3-2 from cracking caused by extreme cold heat of the corundum sleeve 3-2, the four probes are descended at the speed of 3.7mm/s, and when the impedance value on the precise LCR digital bridge 12 suddenly changes from a few K omega or a few M omega to a few omega in the descending process, the probes reach the surface of the KCl solution. The probe is controlled to descend continuously until the four molybdenum rods 3-2 are inserted into the KCl solution for 9mm below the liquid level, and the frequency of the excitation voltage is adjusted and is generally controlled to be 50 kHz-60 kHz. When the measured impedance is at a minimum, the impedance is the total impedance of the KCl solution due to the conductivity k at 35 deg.C of 1mol/L KCl solutionKClKnowing that specific kKClThe constant C, R of the conductivity cell can be calculated and obtained at 0.1311S/cmKCl×kKClWherein R isKClThe impedance of the resulting KCl solution was measured.
It is worth to be noted that the distance between the four corundum sleeves 3-4 can be adjusted by adopting the parallel clamps 11-1 with the same diameter and different sizes, so that the function of controlling the distance between the four molybdenum probes is achieved. In addition, if the length of the exposed probe is too long, resources are wasted, and if the length of the exposed probe is too short, the exposed probe is easy to be bonded with the corundum sleeve 3-4, so that the exposed probe is inconvenient to replace for the next use. The corundum sleeve 3-4 can effectively prevent the molybdenum rod 3-2 from being oxidized, the molybdenum rod 3-2 is conveniently fixed in the corundum sleeve 3-4 by the limiting ring 11-2 above the corundum sleeve 3-4, the corundum sleeve 3-4 is conveniently fixed on the positioning plate 10 by the same-diameter parallel clamp 11-2, and the short circuit caused by the same-diameter parallel clamp 11-1 can be effectively prevented due to the fact that the corundum sleeve 3-4 is an insulator.
Meanwhile, compared with the traditional devices such as a voltmeter, an ammeter and an electrochemical workstation, the precision LCR digital bridge 12 has the advantages of simple operation, high testing speed, accurate testing result and the like. In addition, more importantly, the precise LCR digital bridge 12 can use direct current to test resistance and alternating current to test impedance, and in order to avoid the influence of polarization effect on the experiment, the precise LCR digital bridge 12 is used to test the impedance of the slag, thereby further ensuring the accuracy and stability of the measured data.
And step two, introducing dry high-purity argon into the furnace tube 3-3 of the heating furnace to further protect the molybdenum probe, so as to prevent the molybdenum probe from being oxidized and influencing the accuracy of the measured data.
And step three, preparing high-temperature slag to be detected, placing the high-temperature slag into a crucible 3-1 for heating, controlling the high-temperature slag to be detected to be molten and when the height of the slag is 20-28 mm, then placing the crucible 3-1 onto a base 2 of a heating furnace, heating the high-temperature slag in the crucible 3-1 to a required temperature, uniformly melting the high-temperature slag, and connecting the four molybdenum rods 3-2 with a lead of a precise LCR digital bridge 12.
And step four, controlling the molybdenum rods 3-2 to descend by adopting the lifting system, descending the four molybdenum rods 3-2 at the speed of 3.7mm/s, and reaching the surface of the high-temperature slag when the impedance value on the precise LCR digital bridge 12 is suddenly changed from a few K omega or a few M omega to a few omega.
And step five, continuously controlling the molybdenum rods 3-2 to descend until the four molybdenum rods 3-2 are inserted into the molten slag liquid level by 9mm, ensuring that the positions of the molybdenum rods 3-2 inserted into the molten slag are positioned at the positions of measuring heads when the viscosity-temperature curve is tested in order to avoid the influence of the insufficient length of a furnace constant temperature zone on the experiment, adjusting the frequency of excitation voltage, measuring the impedance of the high-temperature molten slag, and calculating the total conductivity of the high-temperature molten slag. It should be noted that both inductance and capacitance exist in the high-temperature slag, and when the frequency is too low, the capacitance mainly affects the experiment, and the capacitance has the functions of alternating current and direct current resistance, so that the electrical conductivity of the slag is lower than the true value; when the frequency is too high, the inductor mainly influences the experiment, the inductor has the functions of direct current passing and alternating current blocking, and the conductivity of the molten slag is lower than the true value, so that the frequency with the minimum comprehensive influence is selected as the optimal frequency for the experiment test in order to reduce the influence of the capacitance and the inductor on the experiment. In general, the frequency of the mold flux is controlled to an optimum frequency between 2kHz and 6kHz, and this parameter changes depending on the slag, and when the impedance is the minimum value, the impedance is the impedance of the slag, and the electrical conductivity of the high-temperature slag is calculated by using the formula k ═ C/R.
And step six, setting a temperature control system, determining the impedance of the slag in the continuous cooling stage at a required cooling speed (the cooling speed is determined according to the specific characteristics of the high-temperature slag to be measured, and the viscosity-temperature curve of the high-temperature slag to be measured is mainly required to be corresponding to the cooling speed for synchronous analysis), and calculating the total conductivity of the high-temperature slag according to the conductivity cell constant C obtained in the step one.
And seventhly, automatically acquiring the impedance of the molten slag by the computer through a software editing program, drawing a continuous conductivity-temperature curve of the high-temperature molten slag by using the obtained conductivity and temperature data of a plurality of groups of high-temperature molten slag, and calculating to obtain the crystallization starting temperature of the high-temperature molten slag. The specific processing operation is as follows: and drawing tangent lines of curves in different temperature stages by taking 10000/T as an abscissa and ln (k) as an ordinate, and finding out the temperature corresponding to the change of the conductivity along with the temperature change rate through the intersection of the tangent lines, namely the crystallization starting temperature of the slag.
The invention is further described with reference to specific examples.
Example 1
In this example, a reagent for analyzing Chinese medicines was used as a raw material, and the high-temperature melt was composed of No.1 CaO 50.82 wt%, and SiO2＝29.04wt％、Al2O3＝3.13wt％、F-＝10.44wt％、MgO＝1.57wt％、Na2O＝9.4wt％；No.2:*CaO＝39.57wt％、SiO2＝30.43wt％、B2O3＝5wt％、F-＝10wt％、Li2O＝5wt％、Na2O＝5wt％、BaO＝5wt％；No.3:*CaO＝40.83wt％、SiO2＝29.17wt％、B2O3＝5wt％、F-＝10wt％、Li2O＝5wt％、Na2O＝5wt％、BaO＝5wt％；No.4:*CaO＝42.00wt％、SiO2＝28.00wt％、B2O3＝5wt％、F-＝10wt％、Li2O＝5wt％、Na25 wt% of O and 5 wt% of BaO, whereinCaO is CaO +56/78CaF2。
The device and the measuring method are adopted to measure the high-temperature melt in the embodiment, and the specific operation steps are as follows:
1, preparing 40ml of 1mol/L KCl solution by using a 100ml beaker, and putting the solution into a water bath thermostat at the temperature of 35 ℃;
2, fixing the same-diameter parallel clamps on a positioning plate, fixing the corundum sleeves on the same-diameter parallel clamps, and adjusting the distance between the corundum sleeves through the same-diameter parallel clamps;
3, the molybdenum rod penetrates into a hole of the corundum sleeve, the molybdenum rod is fixed in the corundum sleeve through a limiting ring, the lifting rod is adjusted to enable the bottom end of the molybdenum rod to touch the flat upper surface of the horizontally placed heating furnace body, the limiting ring is taken down, and the lifting rod is adjusted to enable the molybdenum rod to be exposed out of the corundum sleeve by a specified length;
4, installing the limiting ring again to ensure that the molybdenum rod is fixed in the corundum sleeve;
connecting the conducting wires of the LCR digital bridge to molybdenum rods, descending the four probes at the speed of 3.7mm/s, suddenly changing the impedance value on the precise LCR digital bridge from a few K omega or a few M omega to a few omega, reaching the surface of the KCl solution, then inserting the four molybdenum electrodes into the KCl solution by 9mm below the liquid level, adjusting the frequency of excitation voltage, and when the impedance is the minimum value, taking the impedance as the total impedance of the KCl solution;
6, calculating a conductivity cell constant;
7, introducing dry high-purity argon in an Ar gas cylinder into the furnace tube from the bottom of the heating furnace;
8, preparing a sample to be tested according to the component requirement, placing the sample into a crucible, ensuring that the height of molten slag is 20-28 mm after the sample to be tested is melted, and then placing the crucible onto a base;
9, heating the high-temperature melt in the crucible to a required temperature to uniformly melt the high-temperature melt;
10, descending the four probes at the speed of 3.7mm/s, and reaching the surface of the slag when the impedance value on the LCR digital bridge suddenly changes from a few K omega or a few M omega to a few omega;
11, inserting a molybdenum rod 9mm below the liquid level of the high-temperature melt, connecting the molybdenum rod with a precise LCR digital bridge, adjusting the frequency of excitation voltage, and when the impedance is the minimum value, taking the impedance as the impedance of the slag;
12, calculating to obtain the total electrical conductivity of the molten slag;
13, setting a temperature control system, measuring the impedance of the slag in the continuous cooling stage at the required cooling speed, and calculating the electrical conductivity of the slag;
15, in addition, in order to compare the accuracy of the high-temperature melt crystallization temperature measured by the method, the viscosity of the high-temperature melt is also tested. The amount of slag used in measuring viscosity was twice the amount used in measuring conductivity.
As can be seen from FIG. 4, the transition temperature of the viscosity-temperature curve of No.1 mold flux is 1203 ℃ and the transition temperature of the conductivity-temperature curve is 1217 ℃, which correspond to the transition temperature 1199 ℃ of the viscosity-temperature curve and the crystallization starting temperature 1219 ℃ of the high temperature confocal measurement reported in the theoretical research and application of the ultra-high alkalinity mold flux for peritectic steel, respectively. In view of the fact that the high-temperature confocal method can avoid the influence of component volatilization, so that the slag crystallization starting temperature can be accurately measured, and the turning temperature obtained through the conductivity-temperature curve is quite consistent with the crystallization starting temperature, which shows that the conductivity-temperature curve test is an important means for accurately obtaining the slag crystallization starting temperature. This is consistent with the conclusion that the temperature at which the electrical conductivity-temperature curve and the viscosity-temperature curve turn is the crystallization starting temperature, as indicated in the patent "a device and method for measuring the crystallization temperature of mold flux of a crystallizer". However, in the patent "a device and method for measuring crystallization temperature of mold flux of crystallizer" using direct current for measurement, data fluctuation is large and unstable, and the measured conductivity-temperature curve is consistent with the inflection temperature on the viscosity-temperature curve, which is in fact in and out, but the conductivity-temperature curve measured by alternating current in this experiment not only avoids the influence of polarization effect, but also the data is more accurate and stable.
Furthermore, it can be seen from FIG. 4 that CaO/SiO is included with the slag2Increase of (d), transition temperature of conductivity-temperature curve and transition temperature of viscosity-temperature curveThe degree is increased, which shows that the crystallization property of the slag is changed along with CaO/SiO2Is increased. It is worth noting that the turning temperature of the electrical conductivity-temperature curve of the slag is higher than the turning temperature of the viscosity-temperature curve, and the turning temperature of the electrical conductivity-temperature curve is the crystallization starting temperature by combining the research in the theoretical research and application of the peritectic steel ultra-high alkalinity covering slag, and the turning temperature of the viscosity-temperature curve is the sudden increase of the viscosity caused after the crystallization reaches a certain value, namely, the electrical conductivity is more sensitive to the crystallization behavior of the slag than the viscosity is to the crystallization behavior of the slag.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims (10)

1. The device for measuring the crystallization starting temperature of the high-temperature slag based on the conductivity is characterized by comprising a conductivity measuring system, a lifting system, a heating system and a temperature control system, wherein:
the conductivity measuring system is used for measuring the conductivity of standard liquid or high-temperature molten slag and comprises a precise LCR digital bridge (12), a corundum sleeve (3-4) and a molybdenum rod (3-2), wherein the molybdenum rod (3-2) is used as a probe and sleeved in the corundum sleeve (3-4), and the top of the molybdenum rod is connected with the precise LCR digital bridge (12) through a conducting wire when the conductivity measuring system is used;
the lifting system is used for controlling the lifting of the molybdenum rod (3-2);
the heating system comprises a heating furnace, a silicon-molybdenum rod (5) and a crucible (3-1), wherein the crucible (3-1) and the silicon-molybdenum rod (5) are positioned in the heating furnace, and high-temperature slag to be detected is filled in the crucible (3-1) and is used for heating the high-temperature slag;
the temperature control system comprises a thermocouple and an electrical control cabinet (13), the thermocouple is arranged on the periphery of the crucible (3-1), the data output end of the thermocouple is connected with the electrical control cabinet (13) and used for inputting a measured temperature signal into the electrical control cabinet (13), and the electrical control cabinet (13) controls the heating temperature according to the received temperature signal.
2. The device for measuring the crystallization starting temperature of the high-temperature slag based on the electrical conductivity is characterized by further comprising an atmosphere control system, wherein the atmosphere control system adopts an Ar gas cylinder (14) and is used for protecting a molybdenum rod (3-2).
3. The device for measuring the crystallization starting temperature of the high-temperature slag based on the electric conductivity according to claim 1 or 2, wherein the electric conductivity measuring system further comprises a positioning plate (10), a same-diameter parallel clamp (11-1) and a limiting ring (11-2), the positioning plate (10) is connected with a lifting system, and the same-diameter parallel clamp (11-1) is fixed on the positioning plate (10) and used for fixing a corundum sleeve (3-4); the molybdenum rod (3-2) is sleeved in the corundum sleeve (3-4) through the limiting ring (11-2).
4. The device for measuring the crystallization starting temperature of the high-temperature slag based on the electric conductivity as claimed in claim 3, wherein the lifting system comprises a mounting frame (9) and a lifting rod (8), and the mounting frame (9) is respectively connected with the positioning plate (10) and the lifting rod (8).
5. The device for measuring the crystallization starting temperature of the high-temperature slag based on the electrical conductivity as claimed in claim 4, wherein the lifting system further comprises a lifting rod driving member, a displacement sensor and a controller, the signal output end of the displacement sensor is connected with the displacement signal input end of the controller, the displacement signal output end of the controller is connected with the lifting rod driving member, and the lifting rod driving member is used for controlling the lifting rod (8) to lift.
6. The apparatus for measuring the crystallization starting temperature of the high-temperature slag based on the electric conductivity as claimed in claim 3, wherein the thermocouple comprises a bottom thermocouple (1) and a side thermocouple (4), the bottom thermocouple (1) is installed at the bottom of the crucible (3-1) and is used for collecting the temperature data of the bottom of the crucible (3-1); the side thermocouple (4) is arranged on the side wall of the crucible (3-1) and is used for collecting temperature data of the side wall of the crucible (3-1); a thermocouple mounting hole, a heating body lead inlet and a gas inlet are processed on the furnace wall (6) of the heating furnace, and the thermocouple is mounted on the furnace wall (6) through the thermocouple mounting hole.
7. A method for measuring the crystallization starting temperature of high-temperature slag based on electric conductivity, which is characterized in that the method is measured by the device of any one of claims 1-6, and comprises the following steps:
measuring the total impedance of standard liquid with known conductivity by using the device by adopting a four-probe method, and calculating to obtain a conductivity cell constant C;
secondly, introducing dry high-purity argon into a furnace tube (3-3) of the heating furnace;
step three, preparing high-temperature slag to be detected, placing the high-temperature slag into a crucible (3-1) for heating, controlling the high-temperature slag to be detected to be molten and when the height of the slag is 20-28 mm, then placing the crucible (3-1) on a base (2) of a heating furnace, heating the high-temperature slag in the crucible (3-1) to the required temperature, uniformly melting the high-temperature slag, and connecting four molybdenum rods (3-2) with a lead of a precise LCR digital bridge;
fourthly, controlling the molybdenum rod (3-2) to descend by adopting the lifting system, so that the molybdenum rod (3-2) reaches the surface of the high-temperature slag;
step five, continuing to control the molybdenum rod (3-2) to descend to 9mm below the liquid level of the high-temperature slag, adjusting the frequency of the excitation voltage, measuring the impedance of the high-temperature slag, and calculating the conductivity of the high-temperature slag;
step six, setting a proper cooling speed, measuring the impedance of the high-temperature slag in the continuous cooling stage, and calculating the total conductivity of the high-temperature slag according to the conductivity cell constant C obtained in the step one;
and step seven, drawing a continuous conductivity-temperature curve of the high-temperature slag according to the conductivity and temperature data of the multiple groups of high-temperature slag obtained in the step six, and calculating to obtain the crystallization starting temperature of the high-temperature slag.
8. The method for measuring the crystallization starting temperature of the high-temperature slag based on the electrical conductivity as claimed in claim 6, wherein in the fourth step, the lowering speed of the molybdenum rod (3-2) is controlled to be 3.7 mm/s; controlling the frequency of the excitation voltage to be 2 kHz-6 kHz, and taking the minimum value of the measured impedance as the impedance of the high-temperature slag; and step six, a temperature control system is arranged to control the cooling speed, and the calculation formula of the electric conductivity of the high-temperature slag is k ═ C/R.
9. The method for measuring the crystallization starting temperature of the high-temperature slag based on the electric conductivity as claimed in claim 6, wherein in the seventh step, the method for calculating the crystallization starting temperature of the high-temperature slag according to the electric conductivity-temperature curve comprises the following steps: and drawing tangent lines of curves in different temperature stages by taking 10000/T as an abscissa and ln (k) as an ordinate, and finding out the temperature corresponding to the change of the conductivity along with the temperature change rate through the intersection of the tangent lines, namely the crystallization starting temperature of the slag.
10. The method for measuring the crystallization starting temperature of the high-temperature slag based on the conductivity as claimed in claim 6, wherein in the step one, a KCl solution is used as a standard solution, and the method for determining the conductivity cell constant C is as follows:
putting a beaker filled with a KCl solution with the concentration of 1mol/L into a constant-temperature water bath kettle, and keeping the temperature of the KCl solution constant at 35 ℃; connecting a lead of the precise LCR digital bridge (12) to the molybdenum rod (3-2), slowly descending the molybdenum rod (3-2), and when the impedance value on the precise LCR digital bridge (12) suddenly changes from a few Komega or a few Momega to a few omega, indicating that the molybdenum rod (3-2) reaches the surface of the solution; then, after thatThe molybdenum rod (3-2) is descended to the liquid level below 9mm, the frequency of the excitation voltage is adjusted to be 50 kHz-60 kHz, when the measured impedance is the minimum value, the impedance is the total impedance of the KCl solution, and the conductivity k of the KCl solution at 35 ℃ is 1mol/LKClKnown as kKCl0.1311S/cm is taken to obtain the conductance cell constant C ═ RKCl×kKClWherein R isKClThe impedance of the resulting KCl solution was measured.
CN202111142814.5A 2021-09-28 2021-09-28 Device and method for measuring crystallization starting temperature of high-temperature slag based on conductivity Withdrawn CN113740374A (en)

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