KR20110127839A - Auxiliary electrode typed sensor and that reference electrode and manufacturing method thereof - Google Patents

Abstract

PURPOSE: An auxiliary electrode type sensor, a reference electrode thereof, and a manufacturing method thereof are provided to reduce manufacturing costs by controlling the excessive consumption of auxiliary electrode materials. CONSTITUTION: A reference electrode of an auxiliary electrode type sensor comprises an auxiliary electrode material(13), a first filler(14), and a second filler(15). The outer surface of a solid electrolyte(12) is coated with the auxiliary electrode material. The closed end of the solid electrolyte is filled with the first filler. The top of a reference electrode material(11) is filled with the second filler. The auxiliary electrode material is not formed on the outer surface of the closed end of the solid electrolyte. The first filler has lower oxygen partial pressure than the reference electrode material.

Description

Auxiliary electrode sensor, standard electrode and manufacturing method thereof AUXILIARY ELECTRODE TYPED SENSOR AND THAT REFERENCE ELECTRODE AND MANUFACTURING METHOD THEREOF

The present invention relates to a negative electrode type sensor for measuring the concentration of the element to be measured included in the molten metal, a standard electrode and a manufacturing method thereof, and more particularly, to reduce the manufacturing cost by suppressing the consumption of expensive negative electrode materials. The present invention relates to a negative electrode type sensor, a standard electrode thereof, and a manufacturing method for reducing an error in component measurement of an element under measurement.

In the metal refining process, the components of the elements to be measured such as Al, Si, and S contained in the molten metal may degrade the mechanical properties of the final product, so they need to be controlled quickly and accurately to an appropriate level.

Here, as a method for measuring the concentration of the element to be measured in the molten metal, as shown in FIG. 1, a probe formed by coating a metal oxide on the outer peripheral surface of the solid electrolyte to form a negative electrode is immersed in the molten metal, and the specific element to be measured. There is a method of measuring by using an electromotive force (Electro-Motvie Force) generated by the equilibrium reaction of the negative electrode with the metal oxide and the oxygen potential difference between the standard electrode material and the molten metal.

Dipping, printing, thermal spraying, etc. may be used as a method of manufacturing the negative electrode type standard electrode. Among these, the dipping type is applied to a slurry in which a binder, a solvent, a reinforcing agent, etc. are mixed. A method of forming a negative electrode by depositing and taking out a solid electrolyte, the adhesiveness of which is different depending on the type of binder, the ratio, the caking additive, the dispersant, the pH, the viscosity of the solvent, etc. It is difficult to maintain it, and there is a problem that peeling phenomenon occurs during immersion depending on the state of the object to be measured, and the printing method is a method of printing a negative electrode material on the surface of the solid electrolyte by a printing device, and the closed end of the solid electrolyte. Coating is difficult, its manufacturing process such as natural drying and sintering process is complicated, and peeling phenomenon is severe due to unevenness of solid electrolyte surface, and response is delayed due to poor sensitivity. There is a problem that a phenomenon occurs.

Therefore, the spray coating method is mainly used. The spray coating method is a method of spraying a secondary electrode material into an electric arc or plasma flame to melt it, and then spraying and colliding with a solid electrolyte at a high speed to coat the coating. Although it does not require treatment and easily adjusts the thickness of the coating layer, the injection of the negative electrode material at high speed requires a very high manufacturing cost, particularly because the coating efficiency of the closed end of the solid electrolyte is very high. Insufficient coating at the end leads to an error in component measurement of the element to be measured in the molten metal, which is difficult to manufacture.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and reduces manufacturing costs by suppressing excessive consumption of expensive negative electrode materials due to low coating efficiency, and inadequate negative electrode material coatings at closed ends of solid electrolytes. It is an object of the present invention to provide a negative electrode type sensor, a standard electrode, and a manufacturing method thereof, by which a measurement error of an element to be measured can be greatly reduced to obtain a highly reliable measurement value for molten steel information.

According to an aspect of the present invention, there is provided a standard electrode including a tubular solid electrolyte, one end of which is closed, and a standard electrode material filled in a mixed state of a metal and a metal oxide in the solid electrolyte. It provides a standard electrode of the negative electrode type sensor comprising a first filler filled in the closed one end side of the solid electrolyte which is a lower side of the standard electrode material, and a second filler filled in the upper side of the standard electrode material.

In this case, the negative electrode material is also characterized in that it is not formed on the outer peripheral surface of the closed end of the solid electrolyte.

In addition, the oxygen partial pressure of the first filler is lower than that of the standard electrode material.

In addition, the oxygen partial pressure of the first filler is lower than the oxygen partial pressure of the second filler.

Here, the first filler is also characterized by consisting of one or more selected from alumina, zirconia, magnesia, titania.

Furthermore, the negative electrode is also characterized by being formed by thermal spray coating.

The present invention also provides a sensor for measuring the concentration of the element to be measured contained in the high-temperature melt part of which is projected to the outside while accommodated in the housing of the probe, the standard electrode of any one of claims 1 to 6, and a high melting point A counter electrode formed of a conductor; A sensor tip including a temperature sensor for measuring a temperature of molten steel; It provides a negative electrode type sensor comprising a cap made of steel or paper surrounding the sensor tip.

And, the present invention comprises the steps of thermally coating the secondary electrode material on the outer peripheral surface of the tubular solid electrolyte closed one end; Filling a first filler in a closed end of the solid electrolyte; Filling a standard electrode material formed of a mixed state of a metal and a metal oxide on an upper side of the first filler; Filling a second filler over the standard electrode material; Inserting a lead wire from the other end of the solid electrolyte to the standard electrode material; It provides a standard electrode manufacturing method of the negative electrode type sensor comprising the step of sealing the other end of the solid electrolyte with a sealing material.

Here, the spray coating step is characterized in that the secondary electrode material is not coated on the outer peripheral surface of the closed end of the solid electrolyte.

The present invention can reduce the manufacturing cost by suppressing excessive consumption of expensive negative electrode material due to low coating efficiency, and greatly reduces the error of component measurement of the element under measurement due to insufficient negative electrode material coating at the solid electrolyte end. It is possible to obtain a highly reliable measurement value for molten steel information, and it is easy to manufacture.

1 is a cross-sectional view showing examples of a conventional standard electrode configuration.
Figure 2 is a cross-sectional view showing an embodiment of a negative electrode type standard electrode configuration according to the present invention.
3 is an explanatory diagram illustrating a principle of a method for measuring the concentration of an element under measurement in the molten metal of the present invention.
Figure 4 is a block diagram showing an example of an assembly including a negative electrode sensor is accommodated sensor tip according to the present invention.
5 is a photograph showing an example of an assembly including a negative electrode type sensor according to the present invention.
6 is a piping diagram of a device for detecting an electrical signal output from the sub-electrode sensor according to the present invention.
7 is a flow chart of a standard electrode manufacturing method of a negative electrode type sensor according to the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is described in detail with reference to drawings.

Solid electrolyte (SOLID ELECTROLYTE TUBE, 12) of the standard electrode 10 according to the present invention is made of Partially Stabilized Zirconia (PSZ) having stability at high temperature as an oxygen ion conductor, as shown in FIG. The shape consists of a tubular tube with one end closed. Originally, zirconia (ZrO ₂ ) is a chemically stable material with high fire resistance, but a particle stabilization occurs due to volume change accompanied by a change in crystal system with temperature rise. One substance selected from CaO, MgO, SrO ₃ , Y ₂ O ₃ is added. As such, when zirconia is stabilized by the partial stabilizer, the zirconia can be used as an oxygen ion conductor because it has electrical characteristics at a high temperature.

The solid electrolyte 12 is filled with a standard electrode material 11 in a mixed state of a metal and a metal oxide, and the standard electrode material 11 is a mixture of Nb and NbO and a mixture of Mo and MoO ₂ . And a mixture of Fe and FeO, Cr and Cr ₂ O ₃ , and a mixture of Ni and NiO, and may be composed of one or more kinds. Each metal and metal oxide are uniformly mixed at an appropriate mixing ratio so as to have excellent high temperature durability.

The outer circumferential surface of the solid electrolyte 12 is formed by coating the negative electrode material 13, the coating method of the negative electrode material does not require a separate drying or post-treatment, spray coating easy to control the thickness of the coating layer ( thermal spray method is preferred.

In addition, it is preferable to coat the coating layer of the negative electrode material 13 only on a part of the outer circumferential surface of the solid electrolyte 12 as shown in FIG. 2, which is particularly solid by spraying the negative electrode material at high speed by thermal spray coating. This is because the coating efficiency of the closed end of the electrolyte 12 is very low, which leads to a high manufacturing cost. Therefore, it is preferable not to form a coating layer of the negative electrode material 13 on the outer circumferential surface of the closed end of the solid electrolyte 12. .

However, when the end portion of the solid electrolyte 12 comes into direct contact with the hot melt, the sub-electrode sensor functions only as an electrochemical sensor, not a sub-electrode type. The sub-electrode reacts with oxygen ions generated by reacting with the element under measurement. Electromotive force by oxygen ions dissolved in molten metal, not by electromotive force, causes a potential difference with the standard electrode material 11 through an end of the solid electrolyte 12 to generate a measured value error of the element under measurement. It is no longer possible to obtain measured values of the element under measurement in the molten metal.

Accordingly, by filling the first filler 14 in the closed end of the solid electrolyte 12 without the negative electrode material 13 coated on the outer circumferential surface thereof, oxygen ions dissolved in the molten metal and the standard electrode material 11 By blocking contact with), only the potential difference by the negative electrode material 13 coated on the side of the solid electrolyte 13 can be measured, thereby enabling accurate measurement of the element under measurement. In this case, the first filler 14 is preferably used by filling with one or more selected from alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), magnesia (MgO), titania (TiO ₂ ). In this case, the oxygen partial pressure of the first filler 14 is preferably lower than the oxygen partial pressure of the standard electrode material 11. This is because induced electromotive force appears as an oxygen potential difference value between the element and the first filler 14, resulting in a measured value error of the element under measurement.

In addition, a lead wire 16 is inserted into the solid electrolyte 12, and C, W, Mo, Re, Ta, Ir, Os, or stainless steel is used.

In addition, the second filler 15 is filled on the upper side of the standard electrode material 11, and may be mainly composed of at least one selected from alumina powder, quartz wool, and quartz tube having excellent heat resistance, and an insulator such as alumina or magnesia. It can also be constructed using a powder of. At this time, the oxygen partial pressure of the first filler 14 is preferably smaller than the oxygen partial pressure of the second filler 15, and the closed end of the solid electrolyte 12 of the standard electrode 10 is in contact with the hot molten metal. When the temperature is very high compared to the other end fixed to the housing 40, the oxygen partial pressure of the inside is immediately increased, and in the case of using a material having the same or higher oxygen partial pressure as the heat-resistant material as the first filler, Since the temperature difference may cause a problem in measuring the element to be measured, the first filler needs to use a material having a lower oxygen partial pressure than the second filler.

The other open side of the solid electrolyte 12 is sealed with a sealing material 17, which is to prevent oxidation of the standard electrode material 11 filled in the solid electrolyte tube, and thermal shock even under high temperature melting conditions. This is to enable fast and accurate measurement without cracks caused by. To this end, the sealing material 17 is preferably formed of heat-resistant cement or molten glass.

3 and 4, the standard electrode 10 according to the present invention described above constitutes a sensor tip together with the counter electrode 20, the temperature sensor 30, the sensor tip is made of a paper tube, etc. The sensor tip is enclosed by a cap 70 made of steel or paper and protected to form a negative electrode type sensor, and the negative electrode type sensor is housed in the housing 40 of the probe. A portion of it protrudes outward to measure the concentration of the element under measurement included in the hot melt. At this time, the counter electrode 20 is made of a high melting point conductor such as molybdenum, steel, and is located on the other surface of the standard electrode 10 to be in contact with the molten steel.

As such, the assembly equipped with the sub-electrode sensor is connected to a high-temperature melt by a separate device provided with a connector 50 for receiving electrical signals from the standard electrode 10, the counter electrode 20, and the temperature sensor 30. It is immersed in 1), it is possible to check the concentration of the components contained in the hot melt within a few seconds, more specifically, as shown in Figure 6 standard electrode 10, counter electrode 20 and temperature sensor 30 Each electrical signal of is transmitted to the calculator 80 as a temperature side electrical signal 71 and an electromotive force signal 72 via the connector 50, and the concentration of the component is automatically calculated by the computer and displayed on the display 86. It can be transmitted to the outside, and it can also be printed and sent by the printer.

Hereinafter, the method for measuring the trace component concentration in the high-temperature melt of the negative electrode type sensor according to the present invention will be described in detail.

Referring to FIG. 3, the metal oxide of the coating layer of the negative electrode material 13 formed on a part of the outer circumferential surface of the solid electrolyte 12 is aluminum oxide when the element to be measured is Al, silicon oxide when Si, and knife when S. A compound of cyan and zirconia is used, and the negative electrode material coating layer reacts with the element to be measured included in the high-temperature melt to generate oxygen ions, and the generated oxygen ions are generated by the oxygen partial pressure difference. Oxygen ions moved into the solid electrolyte 12 and moved into the solid electrolyte 12 become driving force of induced electromotive force in the closed circuit of the calculator 80, and the induced electromotive force is the temperature of the sensor tip. The oxygen concentration in the hot melt, which is input to the sensor together with the thermoelectric power signal, is calculated by Equation 1 obtained by the following thermodynamics.

[Equation 1]

From here,

Pe is the electron conductivity correction coefficient exp (56.23-171,243 / T)

Po ₂ Is the partial pressure of oxygen in the standard electrode (depending on the type of standard electrode material)

K: molten metal O ₂ = Equilibrium constant of 1/2 O

F (Faraday constant) = 2.3052 × 10 ⁴ (Cal / molV)

E (V) is electromotive force (mV)

R (gas constant) = 1.987 (Cal / molK)

T (K) = 273 + Temperature (℃)

Taking the sulfur concentration measurement as an example, the oxygen concentration in the hot melt calculated by the above equation can be inputted into Equation 2 using the equilibrium constant of the following formula, which is the dominant reaction, to estimate the sulfur concentration. have.

Calcia (CaO) of calcium aluminate reacts with sulfur in the hot melt as follows.

CaO + S = CaS + O

And, K '(equilibrium constant) of the formula is a _O / a _S Because of,

&Quot; (2) "

[S] (ppm) ≒ a _s  = a ₀ (ppm) / K ′

By this method, the concentration of the sulfur component contained in the hot melt can be estimated quickly and accurately, and the concentration of the other measured element can also be measured in the same manner.

Hereinafter, a method for manufacturing a standard electrode of a negative electrode type sensor according to the present invention will be described in detail.

As shown in FIG. 7, first, a step S1 of spray coating the negative electrode material 13 on the outer circumferential surface of the tubular solid electrolyte 12 in which one end is closed is performed. A binder is added and uniformly applied to the outer circumferential surface of the solid electrolyte 12 to about 100 μm or less. At this time, the outer peripheral surface of the closed end of the solid electrolyte 12 is not coated with the negative electrode material 13, thereby suppressing excessive consumption of expensive negative electrode materials, thereby reducing manufacturing costs.

After the thermal spraying coating step S1, a step S2 of filling the first filler 14 in the closed end of the solid electrolyte 12 is performed, wherein the first filler is alumina, zirconia, magnesia, Fill one or more selected from titania.

After the filling step (S2) of the first filler is performed a step (S3) of filling a standard electrode material made of a mixed state of a metal and a metal oxide on the upper side of the first filler, the metal so as to have excellent measurement response speed and high temperature durability It is preferable to contain 1-10 weight% of metal oxides with respect to 100 weight% of mixtures of a metal oxide and a metal oxide.

After the filling of the cathode material (S3), the filling of the second filler on the upper side of the cathode material (S4) is performed, wherein at least one selected from alumina powder, quartz wool, and quartz tube having excellent heat resistance is filled. In addition, it can also comprise using powders, such as alumina and magnesia.

After the filling of the second filler (S4), a step (S5) of inserting a lead wire 16 from the other end of the solid electrolyte to the standard electrode material is performed, and the lead wire 16 includes C, W, Mo, and Re. , Ta, Ir, Os, or stainless steel are used and make good contact with the standard electrode material 11. Here, the lead wire 16 may be inserted up to the first filler.

After the lead wire inserting step S5, a step S6 of sealing the other end of the solid electrolyte 12 with a sealing material 17 is performed, which prevents oxidation of the standard electrode material 11 filled in the solid electrolyte tube. This is to measure the concentration of the element to be measured quickly and without cracking due to thermal shock even under high temperature melting conditions. For this purpose, the sealing material 17 is preferably formed of alumina or zirconia-based heat-resistant cement or molten glass.

[Example]

In order to measure the concentration of aluminum as the element to be measured in the high-temperature melt 1, a probe equipped with a negative electrode type sensor including a sensor tip consisting of a standard electrode, a counter electrode, and a temperature sensor was prepared. The common conditions are as follows.

Solid electrolyte: ZrO 2: 95.4 wt%, MgO: 3.6 wt% and other trace elements

* Standard electrode material: Cr + Cr ₂ O ₃ (Including Cr ₂ O ₃ 2 wt%)

* Anode and Coating Method

The main component is alumina (Al ₂ O ₃ ), and 5% CaF2, 30% water, and 10% organic binder are added to the outer peripheral surface of the tubular solid electrolyte. After air drying at room temperature to form a coating layer.

Counter electrode: Molybdenum rod (3mmφ)

Lead wire: molybdenum wire (0.5mmφ)

* 2nd filler

Silica-based quartz wool is filled on the upper side of the standard electrode material in the solid electrolyte, and the quartz tube is put under pressure so that the standard electrode material can be in good contact with the lead wire.

* Temperature Sensor: Thermocouple R Type

* Hot melt: molten steel (C: about 36ppm, Si: about 30ppm or less, Mn: about 470ppm or less, P: about 93ppm or less, S: about 84ppm or less, Al: about 510ppm or less)

* Temperature of high temperature melt: about 1,600 ℃

Under the above conditions, the negative electrode type sensor including the standard electrode, the counter electrode, and the temperature sensor may be mounted at the tip of the protective tube 60 to be immersed in the hot melt 1 to measure and measure the temperature, and to measure the temperature (T) and By using the electromotive force E value, it is processed by the calculator 80 to estimate the concentration of aluminum (Al) in the molten metal.

At this time, the electromotive force (E) value measured using the negative electrode type sensor for measuring aluminum, in which the first filler is not filled as described above, was -150 to -140 mV. According to the invention, when the first filler was filled at the end of the solid electrolyte, the electromotive force (E) value was -160 mV, which is 37-28 × 10 ^-3 % of Al and 49 ×, respectively, at a high temperature of 1,600 ° C. By the electromotive force E representing 10-3% Al, it was confirmed that a significant measurement value error occurred for the element under measurement.

Therefore, by filling the first filler inside the closed end of the solid electrolyte, the negative electrode material is not coated on the outer peripheral surface, it is possible to block the contact between the oxygen ions dissolved in the molten metal and the standard electrode material, thereby Only the potential difference due to the negative electrode material coated on the side of the electrolyte can be measured, thereby reducing the error of the measured value of the element to be measured, thereby enabling accurate measurement.

1. High temperature melt 10. Standard electrode
11.Standard Electrode Material 12.Solid Electrolyte
13. Negative electrode material 14. First filler
15. Second filler 16. Lead wire
17. Sealing material
20. Counter electrode 30. Temperature sensor
40. Housing 50. Connector
60. Sheath 65. Holder
70. Cap 71. Electrical signal on the temperature side
72. Electromotive force signal 80. Calculator

Claims (9)

In a standard electrode comprising a tubular solid electrolyte having one end closed and a standard electrode material filled in a mixed state of a metal and a metal oxide in the solid electrolyte,
A negative electrode material coated on an outer circumferential surface of the solid electrolyte;
A first filler filled in one closed side of the solid electrolyte below the standard electrode material;
The standard electrode of the negative electrode type sensor, characterized in that it comprises a second filler filled on the upper side of the standard electrode material. The method of claim 1,
The negative electrode material is a standard electrode of the negative electrode type sensor, characterized in that not formed on the outer peripheral surface of the closed end of the solid electrolyte. The method of claim 1,
The oxygen partial pressure of the first filler is lower than the oxygen partial pressure of the standard electrode material. The method of claim 1,
The oxygen partial pressure of the first filler is lower than the oxygen partial pressure of the second filler. The method of claim 1,
The first filler is a standard electrode of a negative electrode type sensor, characterized in that made of one or more selected from alumina, zirconia, magnesia, titania. The method of claim 1,
The negative electrode material is a standard electrode of the negative electrode sensor, characterized in that formed by the thermal spray coating. In the sensor which is housed in the housing of the probe, a part of which protrudes outward to measure the concentration of the element to be measured included in the hot melt,
A counter electrode formed of the standard electrode of any one of claims 1 to 6, and a high melting point conductor; A sensor tip including a temperature sensor for measuring a temperature of molten steel;
The negative electrode type sensor, characterized in that it comprises a cap made of steel or paper surrounding the sensor tip. Spray coating a negative electrode material on an outer circumferential surface of the tubular solid electrolyte having one end closed;
Filling a first filler in a closed end of the solid electrolyte;
Filling a standard electrode material formed of a mixed state of a metal and a metal oxide on an upper side of the first filler;
Filling a second filler over the standard electrode material;
Inserting a lead wire from the other end of the solid electrolyte to the standard electrode material;
And sealing the other end of the solid electrolyte with a sealing material. The method of claim 8,
The spray coating step, the method of manufacturing a standard electrode of the negative electrode type sensor, characterized in that the negative electrode material is not coated on the outer peripheral surface of the closed end of the solid electrolyte.

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