JP2023083079A - Oxygen sensor for molten copper, oxygen sensor device for molten copper, method for detecting concentration of oxygen in molten copper, and method for manufacturing copper wire - Google Patents

Abstract

To provide an oxygen sensor for molten copper including a solid electrolyte with high durability, an oxygen sensor device for molten copper, a method for detecting the concentration of oxygen in molten copper, and a method for manufacturing a copper wire.SOLUTION: An oxygen sensor 10 has an oxygen cell 2 that is formed of a zirconia-based solid electrolyte having oxygen ion conductivity, and outputs a detection voltage according to the potential difference generated due to the oxygen concentration difference between the concentration of oxygen in gas supplied to the inside of the oxygen cell 2 and the concentration of oxygen in molten copper with which at least part of the oxygen cell 2 is impregnated. A partially stabilized zirconia in which a zirconia crystal is partially stabilized by a stabilizer is used as the solid electrolyte. The absolute value of the coefficient of thermal expansion of the oxygen cell is 8.2×10-6/K or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to an oxygen sensor for molten copper, an oxygen sensor device for molten copper, a method for detecting oxygen concentration in molten copper, and a method for manufacturing copper wire.

Conventionally, an oxygen sensor is used to measure the oxygen concentration of high-temperature molten copper melted in a melting furnace. Patent Literature 1 describes an oxygen concentration measuring probe previously filed by the present applicant.

This oxygen concentration measuring probe includes a cylindrical external electrode, a solid electrolyte tube placed inside the external electrode, and a reference electrode and an internal electrode placed inside the solid electrolyte tube. A potentiometer is connected between the outer electrode and the inner electrode, and a potential difference signal is sent to the controller. The material of the solid electrolyte tube is stabilized zirconia (ZrO ₂ ⁺ MgO) whose crystal structure is stabilized by magnesium oxide. have. The reference electrode is, for example, a solid oxygen reference electrode using metal/metal oxide such as Fe/FeO powder, or an air reference electrode using gas such as air. The internal electrodes are metal conductor wires made of stainless steel, platinum, or the like. A lower end portion of the solid electrolyte tube serves as an immersion portion protruding downward from the outer conductor. When the immersion part and a part of the cylindrical external electrode are immersed in molten copper, oxygen ions move from the inner surface to the outer surface of the solid electrolyte tube due to the difference in oxygen partial pressure, and between the internal electrode and the external electrode. A potential difference is generated. The control unit receives the potential difference signal output from the potentiometer and monitors the oxygen concentration in the molten copper.

JP 2019-132617 A

As described above, in the oxygen sensor using stabilized zirconia, due to the thermal shock when the immersion part is immersed in molten copper, microcracks (cracks) occur in the solid electrolyte tube after, for example, one or two immersions. there was a case. When such microcracks occur, molten copper enters the cracked portion, and especially when the oxygen concentration in the molten copper is extremely low, the oxygen concentration in the molten copper cannot be detected accurately. confirmed by et al. Therefore, the present inventors have made intensive studies to realize an oxygen sensor with a large average number of times of immersion until microcracks occur, and have completed the present invention.

That is, an object of the present invention is to provide an oxygen sensor for molten copper, an oxygen sensor device for molten copper, a method for detecting oxygen concentration in molten copper, and a method for manufacturing a copper wire, which have a highly durable solid electrolyte that selectively allows oxygen ions to pass through. is to provide

An object of the present invention is to solve the above problems by providing an oxygen cell formed of a zirconia solid electrolyte having oxygen ion conductivity, wherein the oxygen concentration of the gas supplied to the inside of the oxygen cell and the oxygen An oxygen sensor for molten copper that outputs a detection voltage corresponding to a potential difference generated by a difference in oxygen concentration from the oxygen concentration of molten copper in which at least a part of the cell is immersed, wherein a zirconia crystal is stabilized as the solid electrolyte. Provided is an oxygen sensor for molten copper, wherein partially stabilized zirconia partially stabilized with an agent is used, and the absolute value of the coefficient of thermal expansion of the oxygen cell is 8.2×10 ⁻⁶ /K or less.

Further, in order to solve the above problems, the present invention provides the oxygen sensor for molten copper, the voltage detection unit for detecting the voltage between the internal electrode and the external electrode, and the voltage detection unit. An oxygen sensor device for molten copper, comprising a calculation unit that calculates the oxygen concentration of the molten copper based on the detected value.

Further, in order to solve the above problems, the present invention uses the oxygen sensor for molten copper according to claim 6, wherein the internal electrode and the external electrode are made of different metals, and the internal Molten copper oxygen concentration detection, wherein the oxygen concentration of the molten copper is calculated from a value obtained by subtracting the thermoelectromotive force generated due to the difference in material between the electrode and the external electrode from the voltage between the internal electrode and the external electrode. provide a way.

Further, in order to solve the above-mentioned problems, the present invention provides an oxygen sensor for molten copper arranged in a flow path of the molten copper, and the oxygen concentration of the molten copper is continuously detected by the oxygen sensor for molten copper. To provide a method for manufacturing a copper wire in which casting is performed while casting.

ADVANTAGE OF THE INVENTION According to the oxygen sensor for molten copper, the oxygen sensor device for molten copper, the method for detecting the oxygen concentration of molten copper, and the method for manufacturing a copper wire according to the present invention, the durability of the solid electrolyte that selectively allows oxygen ions to pass through is enhanced. becomes possible.

1A is a cross-sectional view showing the configuration of an oxygen sensor device having an oxygen sensor according to an embodiment of the present invention; FIG. (b) is a partially enlarged view of (a). FIG. 2 is a cross-sectional view taken along line AA of FIG. 1; (a) and (b) are perspective views showing the lower end of the oxygen sensor. 1 is a perspective view showing a part of an oxygen sensor using conventionally used stabilized zirconia as a material of an oxygen cell, shown as a comparative example. FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows a schematic structure of the manufacturing apparatus which manufactures a copper wire from a copper raw material.

[Embodiment]
FIG. 1(a) is a cross-sectional view showing the configuration of an oxygen sensor device 1 having an oxygen sensor according to an embodiment of the present invention. FIG. 1(b) is a partially enlarged view of FIG. 1(a). FIG. 2 is a cross-sectional view taken along line AA of FIG. 3(a) and 3(b) are perspective views showing the lower end of the oxygen sensor. In the description of the present embodiment, the terms "upper" and "lower" refer to vertical directions in the state of use of the oxygen sensor. Further, in FIG. 1(a), the symbol M indicates the molten copper, and the symbol _M1 indicates the surface of the molten copper.

(Configuration of oxygen sensor and oxygen sensor device)
The oxygen sensor device 1 includes an oxygen sensor 10 , an oxygen gas supply section 11 , a voltage detection section 12 and a calculation section 13 . The oxygen sensor 10 includes a bottomed cylindrical oxygen cell 2 , a tubular insulating tube 3 made of an electrically insulating material such as alumina, and a pair of metal conductor wires accommodated in the insulating tube 3 . A thermocouple 4 formed by connecting the metal conductor wire 41 and the second metal conductor wire 42, a cylindrical external electrode 5, and a sealing material 6 arranged between the oxygen cell 2 and the external electrode 5 , and a support mechanism 7 that supports the external electrode 5 and biases the insulating tube 3 toward the lower end of the oxygen cell 2 .

The oxygen cell 2 is formed of a zirconia solid electrolyte having oxygen ion conductivity. This solid electrolyte is specifically partially stabilized zirconia obtained by partially stabilizing zirconia (ZrO ₂ ) with a stabilizing agent. Rare earth oxides such as magnesium oxide (MgO), calcium oxide (CaO), and yttrium oxide (Y ₂ O ₃ ) can be used as the stabilizer.

The oxygen cell 2 integrally has a cylindrical portion 21 and a bottom portion 22 , and the bottom portion 22 closes the lower end portion of the cylindrical portion 21 in the vertical direction. A portion of the oxygen cell 2 including the bottom portion 22 forms an immersion portion 20 that protrudes downward from the sealing material 6 and is immersed in the molten copper M. As shown in FIG. The sealing material 6 is made of, for example, a refractory material such as refractory cement, and prevents molten copper M from entering the interior of the external electrode 5 from between the oxygen cell 2 and the external electrode 5 . The temperature of the molten copper M is, for example, 1083° C. or higher and 1200° C. or lower.

As shown in FIG. 2, the insulating tube 3 has first through fourth through holes 31 through 34 formed therein. The first to fourth through holes 31 to 34 penetrate the insulating tube 3 in the longitudinal direction. A part of the insulating tube 3 in the longitudinal direction is arranged inside the oxygen cell 2 , and the other part protrudes upward from the oxygen cell 2 . The outer diameter of the insulating tube 3 is smaller than the inner diameter of the oxygen cell 2, and air (oxygen gas to be described later) is present between the outer peripheral surface 3a of the insulating tube 3 and the inner peripheral surface 21a of the cylindrical portion 21 of the oxygen cell 2. A gap is formed through which the flow can flow.

A first metal conductor wire 41 is inserted through the first through-hole 31 , and a second metal conductor wire 42 is inserted through the second through-hole 32 . The first metal conductor wire 41 and the second metal conductor wire 42 are connected to each other at portions protruding downward from the lower end of the insulating tube 3 . In this embodiment, the ends of the first metal conductor wire 41 and the second metal conductor wire 42 are welded together below the insulating tube 3, and the welded portion becomes a spherical welded portion 43. ing. The welded portion 43 is in contact with the inner surface 22 a of the bottom portion 22 of the oxygen cell 2 .

As an example, the positive electrode first metal conductor wire 41 is made of a platinum rhodium alloy (PtRh) containing 13% rhodium, and the negative electrode second metal conductor wire 42 is made of platinum (Pt). A thermocouple in which such a platinum-rhodium alloy and platinum are combined is generally called an R-thermocouple, and is used to measure temperature in a high temperature range exceeding 1000° C., for example.

Oxygen gas containing a predetermined proportion of oxygen is supplied from the oxygen gas supply unit 11 to the third through hole 33 and the fourth through hole 34 of the insulating tube 3 . As an example, this oxygen gas is pure oxygen with an oxygen content of 100%, but if the oxygen content is known, it may be air with an oxygen content of about 21%. Oxygen gas is supplied to the third through-hole 33 and the fourth through-hole 34 from the upper end of the insulating tube 3 , and the supplied oxygen gas escapes to the lower end of the insulating tube 3 . The oxygen gas that escapes to the lower end of the insulating tube 3 is discharged above the oxygen cell 2 through the gap between the insulating tube 3 and the oxygen cell 2 . The amount of oxygen gas supplied from the oxygen gas supply unit 11 is such that the oxygen concentration inside the oxygen cell 2 is kept constant.

The external electrode 5 has a cylindrical shape with open upper and lower ends, and is arranged outside the oxygen cell 2 . A sealing material 6 seals between the inner peripheral surface 5 a at the lower end of the external electrode 5 and the outer peripheral surface 21 b of the cylindrical portion 21 of the oxygen cell 2 . The external electrode 5 supports the oxygen cell 2 via the sealing material 6 . In this embodiment, the external electrodes 5 are made of stainless steel. More specifically, SUS310S (JIS G 4303), which has excellent heat resistance, can be preferably used as this stainless steel. A portion of the insulating tube 3 protrudes upward from the upper end of the external electrode 5 .

The support mechanism 7 includes a holding member 71 that holds the upper end of the external electrode 5 , a lid member 72 that is fixed to the holding member 71 and covers a part of the upper end opening of the external electrode 5 , and an outer peripheral surface 3 a of the insulating tube 3 . and a coil spring 74 disposed between the spring receiving member 73 and the lid member 72 . The holding member 71 integrally has a fitting cylinder portion 711 in which the upper end portion of the external electrode 5 is fitted, and a plate portion 712 to which the lid member 72 is fixed by a plurality of bolts 70 . An insertion hole 721 through which the insulating tube 3 is inserted is formed in the cover member 72 , and the upper end portion of the insulating tube 3 protrudes upward from the insertion hole 721 . The coil spring 74 presses the insulating tube 3 downward by its restoring force. As a result, the welded portion 43 of the thermocouple 4 is pressed against the inner surface 22a of the bottom portion 22 of the oxygen cell 2 and is in contact therewith.

The oxygen sensor 10 configured as described above operates according to the oxygen concentration difference between the oxygen gas supplied to the inside of the oxygen cell 2 and the oxygen concentration of molten copper in which at least a part of the oxygen cell 2 is immersed. A detection voltage corresponding to the generated potential difference is output. Due to the oxygen partial pressure difference between the inside and the outside of the oxygen cell 2, this potential difference changes from the inner surface 2a of the oxygen cell 2 (the inner peripheral surface 21a of the cylindrical portion 21 and the inner surface 22a of the bottom portion 22) to the outer surface 2b of the oxygen cell 2 in the immersion portion 20. It is generated by movement of oxygen ions toward (the outer peripheral surface 21b of the cylindrical portion 21 and the outer surface 22b of the bottom portion 22).

That is, on the side of the inner surface 2a where the oxygen concentration is relatively high, oxygen molecules take in electrons and become oxygen ions (O ₂ +4e ⁻ →2O ²⁻ ), and on the side of the outer surface 2b where the oxygen concentration is relatively low, the oxygen ions convert to electrons. and return to molecular oxygen (2O ²⁻ →O ₂ +4e ⁻ ). As a result, an electromotive force corresponding to the oxygen partial pressure difference is generated. The electromotive force due to this oxygen partial pressure difference is expressed by the following relational expression (Nernst's formula) with the temperature (absolute temperature) of the oxygen cell 2 as a coefficient.

E=(RT/(nF))×ln(PO ₂ (A)/PO ₂ (B))
In this formula,
E is the electromotive force [V] generated by the oxygen partial pressure difference
R is the gas constant (8.3144598 [J・mol ⁻¹・K ⁻¹ ])
T is absolute temperature [K]
n is the number of electrons involved in the reaction (n = 4 in the above reaction)
F is the Faraday constant (96485.3329 [C mol ^-1 ])
PO ₂ (A) is the oxygen partial pressure [atm] on the high concentration side (inside the oxygen cell 2)
PO ₂ (B) is the oxygen partial pressure [atm] on the low concentration side (outside the oxygen cell 2)
is. Then, if E and T are known (PO ₂ (A) is known), PO ₂ (B) can be obtained from the above formula, and further the oxygen concentration of molten copper M can be obtained from PO ₂ (B). can.

(Molten copper oxygen concentration detection method)
Next, a method for detecting the oxygen concentration of the molten copper M in the oxygen sensor device 1 will be described.

As shown in FIG. 1( a ), the potential of the first metal conductor wire 41 and the second metal conductor wire 42 of the thermocouple 4 and the potential of the external electrode 5 are input to the voltage detector 12 . The voltage detection unit 12 detects the voltage (potential difference) between the first metal conductor wire 41 and the second metal conductor wire 42, and uses the second metal conductor wire 42 as the internal electrode 40. A voltage (potential difference) between 40 and the external electrode 5 is detected. That is, in the present embodiment, of the first metal conductor wire 41 and the second metal conductor wire 42, the second metal conductor wire 42 is adjusted according to the oxygen concentration difference between the inside and the outside of the oxygen cell 2. It is used as an internal electrode 40 for detecting voltage. However, the invention is not limited to this, and the first metal conductor wires 41 may be used as internal electrodes.

A portion of the external electrode 5 in the longitudinal direction including the lower end is immersed in the molten copper M together with the immersion portion 20 of the oxygen cell 2 . Thereby, the external electrode 5 and the outer surface 2b of the oxygen cell 2 in the immersion portion 20 are electrically connected via the molten copper M. In this embodiment, since the external electrode 5 is made of stainless steel as described above, the internal electrode 40 (the second metal conductor wire 42 made of platinum) and the external electrode 5 are made of different metals.

Hereinafter, the voltage between the first metal conductor wire 41 and the second metal conductor wire 42 will be referred to as the temperature sensitive voltage, and the voltage between the internal electrode 40 and the external electrode 5 will be referred to as the oxygen concentration sensitive voltage. The voltage detection unit 12 has an AD converter, and outputs to the calculation unit 13 a digital signal obtained by converting the detected values of the temperature sensitive voltage and the oxygen concentration sensitive voltage into digital values. The calculation unit 13 calculates the oxygen concentration of the molten copper M based on the detection value output by the voltage detection unit 12 .

In calculating the oxygen concentration of the molten copper M, the calculation unit 13 first obtains the temperature of the oxygen cell 2 (T in the above relational expression) based on the temperature sensitive voltage. The temperature of the oxygen cell 2 corresponds to the temperature of the molten copper M. Next, the calculation unit 13 obtains the thermoelectromotive force generated due to the difference in material between the internal electrode 40 and the external electrode 5 based on the obtained temperature, subtracts the obtained thermoelectromotive force from the oxygen concentration sensitive voltage, and obtains An electromotive force (E in the above relational expression) due to the oxygen partial pressure difference between the inside and outside of the oxygen cell 2 is obtained. Then, the obtained E and T are applied to the above relational expression to obtain the oxygen concentration of the molten copper M.

(Material of oxygen cell)
Next, the details of the material of the oxygen cell 2 will be described. As is well known, pure zirconia without any stabilizers is monoclinic at room temperature, but changes from monoclinic to tetragonal and then from tetragonal to cubic with increasing temperature. and the crystal structure changes. This phase transition is accompanied by a volume change, and volume contraction occurs in the phase transition from monoclinic to tetragonal, and volume expansion occurs in the phase transition from tetragonal to cubic. Due to this volume change, microcracks are likely to occur, especially when the temperature changes abruptly. On the other hand, when a stabilizer is added to zirconia, cubic crystals are stable even at room temperature, and mechanical properties such as strength and toughness are improved compared to zirconia without stabilizers. Are known.

In partially stabilized zirconia, not all zirconia crystals are cubic at room temperature, and single crystals and tetragonal crystals are dispersed. The present inventors have confirmed that partially stabilized zirconia is less prone to microcracks than stabilized zirconia with a stabilization rate of 100%. The reason for this is that when a crack occurs, the tetragonal crystals around it change to monoclinic crystals due to stress-induced transformation, and volume expansion occurs, which generates a force that suppresses the propagation of the crack, preventing the crack from propagating. This is thought to be for the purpose of suppressing

FIG. 4 is a perspective view showing a part of an oxygen sensor 10A as a comparative example, in which conventionally used stabilized zirconia is used as the material of the oxygen cell 2A. In FIG. 4, a portion of the immersion portion 20A of the oxygen cell 2A is cut horizontally and removed to show the inside of the oxygen cell 2A. This oxygen sensor 10A is constructed in the same manner as the oxygen sensor 10 described above, except that the material of the oxygen cell 2A is different.

As shown in FIG. 4, if the oxygen cell 2A is immersed in molten copper without being sufficiently preheated, minute cracks C may occur due to rapid volumetric changes, and molten copper M may enter these minute cracks C. The molten copper M that has entered the microcracks C forms a current path that short-circuits the inside and outside of the oxygen cell 2A, and the voltage generated between the internal electrode 40 (second metal conductor wire 42) and the external electrode 5 increases the oxygen cell It deviates from the value corresponding to the oxygen concentration difference between the inside and outside of 2A. Therefore, there is a possibility that the oxygen concentration cannot be measured with high accuracy, especially in a low oxygen concentration range of 20 ppm or less.

The present inventors have adjusted the stabilization rate of the zirconia crystal by adjusting the amount of the stabilizer added, so that the thermal expansion coefficient of the partially stabilized zirconia is set to a predetermined value or less, and when immersed in molten copper M, The inventors have found that it is possible to suppress the occurrence of microcracks in the immersion portion 20 of the oxygen cell 2 . Then, experiments were repeated in which a large number of prototypes with different amounts of stabilizer added were immersed in molten copper M, and the following (1) to (3) were selected as the material for the oxygen cell 2 of the oxygen sensor 10 for molten copper. It was found that the use of partially stabilized zirconia that satisfies the conditions can greatly suppress the occurrence of microcracks compared to conventional ones.
(1) The stabilization rate of zirconia crystals is 10% or more and 50% or less (2) The absolute value of the coefficient of thermal expansion is 8.2×10 ⁻⁶ /K or less (3) Contains a stabilizer The amount is 2 mol% or more and 9 mol% or less

Here, "the zirconia crystal stabilization rate is 10% or more and 50% or less" means that the proportion of cubic zirconia crystals at room temperature is 10 to 50%. Further, "the absolute value of the coefficient of thermal expansion is 8.2×10 ^-6 /K or less" means that the absolute value of the coefficient of thermal expansion is within the operating temperature range (room temperature to molten copper temperature) of the oxygen sensor 10. It means 8.2×10 ⁻⁶ /K or less over the entire area. In particular, it is desirable that the absolute value of the average coefficient of thermal expansion is 8.2×10 ⁻⁶ /K or less at a temperature of 20° C. or higher and 1000° C. or lower.

Further, when magnesium oxide (MgO) or calcium oxide (CaO) is used as the stabilizer, the lower limit of the content of the stabilizer in the partially stabilized zirconia is desirably 7 to 8 mol %. If the stabilization rate (stabilizer concentration) of the partially stabilized zirconia is too low, the mechanical strength of the partially stabilized zirconia against heat deteriorates, so the oxygen concentration contained in the molten copper M is continuously measured. This is because it is not suitable for applications where

(Copper wire manufacturing equipment and manufacturing method)
Next, with reference to FIG. 5, a copper wire manufacturing apparatus and manufacturing method will be described. FIG. 5 is a configuration diagram showing a schematic configuration of a manufacturing apparatus 8 that manufactures a copper wire from a copper raw material. This manufacturing apparatus 8 is a continuous casting and rolling apparatus for continuously casting and rolling a copper wire (copper wire rod), which is a copper alloy material.

The manufacturing apparatus 8 includes a melting furnace 80 that heats and melts the copper raw material, an upper gutter 81 that transfers the molten copper flowing out of the melting furnace 80, and the molten copper transferred by the upper gutter 81, which is temporarily A holding furnace 82 for storage, a metal element adding device 83 for adding a metal element to the molten copper, a lower gutter 84 for transferring the molten copper to which the metal element has been added by the metal element adding device 83, and A tundish 85 for temporarily storing the molten copper, a pouring nozzle 86 for flowing out the molten copper from the tundish 85, a continuous casting machine 87, and a casting bar 91 transferred from the continuous casting machine 87 are continuously operated. It has a hot rolling device 88 for rolling and a winder (coiler) 89 for winding the copper wire 92 transported from the hot rolling device 88 through the surface cleaning treatment device.

The metal elements added to the molten copper by the metal element addition device 83 are, for example, titanium (Ti), indium (In), tin (Sn), magnesium (Mg), and the like. In some cases, no metal element is added to the molten copper, and in this case, the metal element addition device 83 is not required.

The continuous casting machine 87 is a device for continuous casting of a belt-wheel type, and includes a casting ring (casting wheel) 871 having grooves formed on its outer periphery, a belt (casting belt) 872, and a cylindrical caster holding the casting ring 871. and a holding portion 873 of . The casting ring 871 is rotationally driven by a motor (not shown). The belt 872 is guided by a plurality of pulleys 874 and circulates while contacting part of the outer peripheral surface of the casting ring 871 .

Molten copper flowing down from the tundish 85 through the pouring nozzle 86 is supplied between the groove of the casting ring 871 and the belt 872 . The casting ring 871 and belt 872 are cooled by cooling water while rotating. Molten copper supplied to the continuous casting machine 87 is cooled and solidified between a casting ring 871 and a belt 872 to form a rod-shaped casting bar (cast material) 91 .

The oxygen sensor 10 is arranged in the molten copper flow path from the melting furnace 80 to the continuous casting machine 87 . Casting is performed while the oxygen sensor 10 continuously detects the oxygen concentration of the molten copper. Here, "continuous detection" means that the oxygen concentration is constantly detected without interruption while the immersion portion 20 is immersed in molten copper from the start to the end of the production of the cast material (here, the cast bar 91). It means to detect.

The position of the oxygen sensor 10 may be the upper gutter 81, the holding furnace 82, or the lower gutter 84, but it is more desirable to place it in the tundish 85 immediately before being supplied to the continuous casting machine 87. In particular, it is more desirable to dispose it directly above the pouring nozzle 86 inside the tundish 85 . By arranging the oxygen sensor 10 in this way, for example, even if the sealing of the upper gutter 81 or the lower gutter 84 becomes insufficient for some reason and the oxygen concentration changes in the flow path, it can be detected. This is because It is also effective to dispose a plurality of oxygen sensors at a plurality of locations as described above. In this way, if there is a change in the oxygen concentration indicated by, for example, the oxygen sensor directly above the pouring nozzle 86 during operation, it is possible to know which part upstream caused the change.

The oxygen concentration of the molten copper detected by the oxygen sensor 10 varies depending on, for example, oxygen-free copper with a residual oxygen content of 10 ppm or less, low-oxygen copper with a residual oxygen content of 20 ppm or less, and tough pitch copper with a purity of about 99.9%. It is used for quality control such as Also, the oxygen concentration of the molten copper detected by the oxygen sensor 10 can be used to control the amount of active metals such as titanium and magnesium added by the metal element adding device 83 . Titanium and magnesium easily combine with oxygen, and the oxygen concentration in the molten copper changes depending on the amount of these added, so it is possible to estimate the amount of active metal added from the oxygen concentration in the molten copper.

The temperature detected by the thermocouple 4 is used to calculate the oxygen concentration using the above relational expression, and is used to check whether the preheating of the oxygen cell 2 is performed properly. can be used for By preheating the oxygen cell 2, the generation of microcracks can be suppressed more reliably. A specific preheating method is not particularly limited, but preheating may be performed, for example, by a gas burner, and the immersion portion 20 of the oxygen cell 2 is brought close to the surface of the molten copper before immersion in the molten copper. can also be done by

(Experimental result)
Table 1 shows solid electrolytes using magnesium oxide (MgO) as a stabilizer, a stabilizer concentration of 9 mol%, a stabilization rate of 30%, and an absolute value of the coefficient of thermal expansion of 6.2×10 ⁻⁶ K. [Example 1], using yttrium oxide (Y ₂ O ₃ ) as a stabilizer, the stabilizer concentration is 8 mol%, the stabilization rate is 100%, and the absolute value of the thermal expansion coefficient is 10 An oxygen cell formed by a solid electrolyte of 1×10 ⁻⁶ K [Comparative Example 1], and calcium oxide (CaO) as a stabilizer, with a stabilizer concentration of 15 mol % and a stabilization rate of 100%. , Using an oxygen cell [Comparative Example 2] formed of a solid electrolyte having a coefficient of thermal expansion with an absolute value of 10.2×10 ⁻⁶ K, a table showing the results of measuring the average number of repeated immersion measurements. be.

この表１に示す繰り返し浸漬測定可能回数の平均値の計測方向は、次のステップ１～５の通りである。

The measurement direction of the average value of the possible number of repeated immersion measurements shown in Table 1 is as shown in steps 1 to 5 below.

(Step 1) Three types of oxygen sensors for molten copper using the oxygen cells shown in Example 1, Comparative Example 1, and Comparative Example 2 are prepared as test samples.
(Step 2)
For the first test sample of each of the three types of oxygen sensors for molten copper, "preheat ⇒ immerse in molten copper made of pure copper kept at about 1200 ° C (1 hour) ⇒ pull out from molten copper and slowly cool". One cycle (once, about 1.5 hours) is performed.
(Step 3)
It is determined whether or not the oxygen concentration can be measured during immersion in one cycle, and whether or not cracks have occurred in the test sample at the end of slow cooling in one cycle.
(Step 4)
If the determination result in step 3 shows that the oxygen concentration can be measured during immersion in molten copper and no cracks have occurred in the test sample, repeat the same cycle as in step 2 for the test sample. , and then step 3 is determined. On the other hand, if the oxygen concentration cannot be measured during immersion in molten copper, or if cracks occur in the test sample, replace it with the next test sample of the same type and The same cycle as in step 2 is performed, and then the determination of step 3 is performed.
(Step 5)
For each of the three types of test samples, if an abnormality is found in the determination of step 3 in the third test sample, the test for that type of test sample is terminated. Then, the average value of the number of cycles in which the judgment result of step 3 was passed in the three test samples is calculated.

In the measurements in steps 1 to 5 above, with the oxygen sensor for molten copper using the oxygen cell according to Example 1, the average value obtained in step 5 was It was greater than the average value determined in step 5 for the oxygen sensor. Further, in the oxygen sensor for molten copper using the oxygen cell according to Example 1, the number of cycles at which the determination result of step 3 was acceptable for all three oxygen cells was the same as that for melting using the oxygen cells according to Comparative Examples 1 and 2. It was more than the number of cycles in which the judgment result of step 3 was passed in the oxygen sensor for copper. That is, the oxygen sensor for molten copper using the oxygen cell according to Example 1 exhibited stable and high durability.

(Actions and effects of the embodiment)
According to the embodiment described above, it is possible to suppress the occurrence of microcracks in the oxygen cell 2 and improve the durability of the oxygen sensor 10 . Further, by using the second metal conductor wire 42 that constitutes the thermocouple 4 as the internal electrode 40, the number of parts of the oxygen sensor 10 can be suppressed and the cost can be reduced.

(Summary of embodiment)
Next, technical ideas understood from the embodiments described above will be described with reference to the reference numerals and the like in the embodiments. However, each reference numeral in the following description does not limit the constituent elements in the claims to the members and the like specifically shown in the embodiment.

[1] Provided with an oxygen cell (2) formed of a zirconia solid electrolyte having oxygen ion conductivity, the oxygen concentration of the gas supplied to the inside of the oxygen cell (2) and the oxygen cell (2) An oxygen sensor for molten copper (10) that outputs a detection voltage corresponding to a potential difference generated by a difference in oxygen concentration from the oxygen concentration of molten copper (M) in which at least a portion is immersed, wherein the solid electrolyte is zirconia Partially stabilized zirconia whose crystals are partially stabilized by a stabilizer is used, and the absolute value of the coefficient of thermal expansion of the oxygen cell (2) is 8.2×10 ⁻⁶ /K or less. oxygen sensor (10).

[2] The oxygen sensor for molten copper according to [1] above, wherein the content of the stabilizer in the partially stabilized zirconia is 2 mol % or more and 9 mol % or less.

[3] The oxygen sensor for molten copper (10) according to the above [1] or [2], wherein the zirconia crystal in the oxygen cell (2) has a stabilization rate of 10% or more and 50% or less.

[4] A thermocouple (4) formed by connecting a pair of metal conductor wires (41, 42), wherein a connection point (43) of the pair of metal conductor wires (41, 42) is the oxygen cell (2) One of the pair of metal conductor wires (41, 42) arranged to contact the inner surface is used as an internal electrode (40) for detecting the potential difference. The oxygen sensor for molten copper (10) according to any one of [1] to [3].

[5] A metal conductor arranged outside the oxygen cell (2) to support the oxygen cell (2), and for detecting the potential difference between the metal conductor and the internal electrode (40) The oxygen sensor for molten copper (10) according to the above [4], which is used as an external electrode (5).

[6] The molten copper oxygen sensor (10) according to [5] above, a voltage detection section (12) for detecting a voltage between the internal electrode (40) and the external electrode (5), and An oxygen sensor device for molten copper (1), comprising a calculation unit (13) for calculating the oxygen concentration of the molten copper (M) based on the detected value of the voltage detection unit (12).

[7] The internal electrode (40) and the external electrode (5) are made of different metals, and the computing unit (13) is configured to The oxygen sensor device for molten copper according to the above [6], wherein the oxygen concentration of the molten copper (M) is calculated from the value obtained by subtracting the thermoelectromotive force generated due to the difference in the voltage detection unit (12) from the value detected by the voltage detection unit (12). (1).

[8] Using the oxygen sensor (10) for molten copper according to [5], wherein the internal electrode (40) and the external electrode (5) are made of dissimilar metals of different materials, the internal electrode (40 ) and the external electrode (5) by subtracting the thermoelectromotive force generated by the difference in material from the voltage between the internal electrode (40) and the external electrode (5). A molten copper (M) oxygen concentration detection method for calculating the oxygen concentration.

[9] The oxygen sensor for molten copper (10) according to any one of [1] to [5] above is arranged in the flow path of the molten copper (M), and the oxygen sensor for molten copper (10) A method for producing a copper wire (91) in which casting is performed while continuously detecting the oxygen concentration of molten copper (M).

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the scope of claims. Also, it should be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

DESCRIPTION OF SYMBOLS 1... Oxygen sensor apparatus 10, 10A... Oxygen sensors 2, 2A... Oxygen cell 20, 20A... Immersion part 3... Insulating tube 4... Thermocouple 40... Internal electrode 41... First metal conductor wire 42... Second metal conductor Wire 43 Welded portion 5 External electrode 6 Sealing material 7 Support mechanism 8 Manufacturing apparatus

Claims (9)

An oxygen cell comprising a zirconia solid electrolyte having oxygen ion conductivity, the oxygen concentration of a gas supplied to the inside of the oxygen cell and the oxygen concentration of molten copper in which at least part of the oxygen cell is immersed. An oxygen sensor for molten copper that outputs a detection voltage according to the potential difference generated by the oxygen concentration difference between
Partially stabilized zirconia in which zirconia crystals are partially stabilized by a stabilizer is used as the solid electrolyte,
The absolute value of the coefficient of thermal expansion of the oxygen cell is 8.2×10 ⁻⁶ /K or less,
Oxygen sensor for molten copper. The content of the stabilizer in the partially stabilized zirconia is 2 mol% or more and 9 mol% or less,
The oxygen sensor for molten copper according to claim 1. The stabilization rate of the zirconia crystal in the oxygen cell is 10% or more and 50% or less,
The oxygen sensor for molten copper according to claim 1 or 2. A thermocouple formed by connecting a pair of metal conductor wires is arranged so that a connection point of the pair of metal conductor wires is in contact with the inner surface of the oxygen cell,
using one of the pair of metal conductor wires as an internal electrode for detecting the potential difference;
The oxygen sensor for molten copper according to any one of claims 1 to 3. a metal conductor disposed outside the oxygen cell to support the oxygen cell, the metal conductor being used as an external electrode for detecting the potential difference with the internal electrode;
The oxygen sensor for molten copper according to claim 4. 6. The oxygen sensor for molten copper according to claim 5, a voltage detection unit that detects the voltage between the internal electrode and the external electrode, and the oxygen concentration of the molten copper based on the detected value of the voltage detection unit. A computing unit that calculates
Oxygen sensor device for molten copper. the internal electrode and the external electrode are made of different metals,
The calculation unit calculates the oxygen concentration of the molten copper from the value obtained by subtracting the thermoelectromotive force generated by the difference in material between the internal electrode and the external electrode from the value detected by the voltage detection unit.
The oxygen sensor device for molten copper according to claim 6. Using the oxygen sensor for molten copper according to claim 5, wherein the internal electrode and the external electrode are made of dissimilar metals of different materials,
calculating the oxygen concentration of the molten copper from the value obtained by subtracting the thermoelectromotive force generated due to the difference in material between the internal electrode and the external electrode from the voltage between the internal electrode and the external electrode;
Method for detecting oxygen concentration in molten copper. The molten copper oxygen sensor according to any one of claims 1 to 5 is arranged in the molten copper flow path, and the molten copper oxygen sensor continuously detects the oxygen concentration of the molten copper while casting. A method of manufacturing a copper wire.

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