JPH11118754A - Device for measuring oxygen concentration in melted metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a slug in a melted metal from being adhered to a solid electrolyte, relieve a thermal shock when inserting or pulling up an oxygen probe into or from the melted metal, and further prevent the contact with the melted metal of an immobilizing agent for immobilizing the solid electrolyte to an external electrode. SOLUTION: An inner protection pipe 10 and an outer protection pipe 11 are placed on a probe 1. The inner protection pipe 10 consists of a non-porous body and is placed at an outer periphery being dipped into a melted metal 8 of an external electrode 6 excluding a probe bottom part 1a. An inner protection pipe lower edge 10a projects from an outer electrode lower edge 6a, forms a recess 12 at an area to a solid electrolyte bottom part 2a, confines a gas 14, and breaks the contact between the melted metal 8 and an immobilizing agent 7. The amount of projection is smaller lower than the height of the electrolyte bottom part 2a and secures the contact between the electrolyte bottom part and the melted metal. The outer protection pipe 11 consists of a porous body for transmitting the melted metal 8 but rejects the transmission of a slug and is overlapped to and is placed on the outer periphery of the probe bottom part 1a and the inner protection pipe 10. An air gap 15 is formed at an area to the probe bottom part 1a, so that melted metal 8 through the outer protection pipe 11 can stay in the air gap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen concentration measuring device for measuring the amount of oxygen contained in a molten metal, and more particularly to a protective structure for an oxygen probe immersed in the molten metal.

[0002]

2. Description of the Related Art The oxygen concentration (containing 0.02 to 0.05%) in molten metal during casting, particularly in tough pitch copper, which is generally used as a conductive material, depends on the electrical or mechanical properties of a molded product. In addition, it greatly affects workability. Therefore, it is important to control this to an appropriate value, and an oxygen concentration measuring device for continuously or continuously measuring the oxygen concentration in molten copper at the time of casting has been developed.

[0003] The detection unit of the conventional oxygen concentration measuring apparatus is shown in FIG.
As shown in FIG. 1, an oxygen concentration cell is formed by using an external electrode 6, a solid electrolyte 2, and a standard electrode 5, and is a measuring device based on an electrochemical principle, and is called an oxygen probe 1. It has a cylindrical external electrode 6 opened up and down, and a crucible made of an oxygen ion conductor fixed in the open lower part of the external electrode 6 with a fixing agent 7 and having a bottom 2 a protruding from the lower end of the external electrode 6. And a standard electrode 5 made of a metal-metal oxide provided in the solid electrolyte 2.

The materials used in such an oxygen concentration measuring device are as follows. First, as the solid electrolyte 2, for example, magnesia (MgO), yttria (Y ₂ O ₃ ), calcia (C
zirconia (ZrO ₂ ), HfO
₂ , ThO ₂ , CeO _{2 and the} like are used. Of these, stabilized zirconia, which has stable strength and is inexpensive, is mainly used. The external electrode 6 is made of heat-resistant steel or the like, and the fixing agent 7 for fixing the solid electrolyte 2 to this is a heat-resistant cement such as alumina or zircon. A noble metal such as platinum is used for the lead wire 3 fixed to the inner bottom of the crucible-shaped solid electrolyte 2, pulled out from the external electrode 6 and connected to the voltmeter 9.

The standard electrode 5 made of metal-metal oxide filled inside the solid electrolyte 2 has, for example, Fe
_{-FexO 2, Ni-NiO, Mo} -MoO 2, Cr-
Cr ₂ O ₃ or the like is used. Such a known electrode having a constant oxygen concentration (activity) is used as a standard electrode 5, and the molten copper 1 of the object to be measured is sandwiched between the solid electrolyte 2 through which oxygen ions conduct.
8 (external electrode 6) and the standard electrode 5, an oxygen concentration cell is formed, and the electromotive force generated between the electrodes 5 and 6 is measured by a voltmeter 9 based on the electrochemical principle. The concentration can be measured.

FIG. 2 shows the solid electrolyte 2
A metal-metal oxide standard electrode is formed therein, and an air standard electrode is also formed in some cases.

[0007]

In order to measure the oxygen concentration in the molten copper using the above-described conventional oxygen concentration measuring device,
It is necessary to immerse the oxygen probe 1 in the molten copper pool or in the molten copper flow, but at this time, there are the following problems.

(1) The solid electrolyte of the oxygen probe is mechanical,
The thermal shock tends to cause breakage and cracks, and particularly when inserted or pulled into molten copper, cracks are likely to occur due to the thermal shock, making measurement impossible.

(2) Copper oxide, CaO, Si
Oxides such as O ₂ , MgO, and P ₂ O ₅ (hereinafter, referred to as slag) may be mixed. When inserting or pulling up an oxygen probe, these slags are added to the solid electrolyte of the oxygen probe. If touched, an erroneous electromotive force is generated, so that accurate measurement cannot be performed. In particular, zirconia used for the solid electrolyte is liable to adhere to slag, and is difficult to remove once adhered to slag.

(3) The fixing agent between the solid electrolyte and the external electrode comes into contact with the molten copper to cause reaction degradation, which also affects the solid electrolyte and easily affects the electromotive force value, making accurate measurement impossible. .

The problems (1) to (3) are not limited to molten copper, but are common to molten metals.

An object of the present invention is to eliminate the above-mentioned problems of the prior art by mounting a protective tube on the outside of the oxygen probe so that when the oxygen probe is immersed in the molten metal,
Prevents slag contained in the molten metal from adhering to the solid electrolyte, reduces thermal shock when inserting or pulling the oxygen probe into the molten metal, and further fixes the gap between the solid electrolyte and external electrodes An object of the present invention is to provide an apparatus for measuring an oxygen concentration in a molten metal which can prevent a reaction between a fixing agent and a molten metal and measure oxygen concentration continuously and with high accuracy for a long time.

[0013]

According to a first aspect of the present invention, there is provided an apparatus for measuring the concentration of oxygen in molten metal, comprising: a cylindrical external electrode; and a fixing agent fixed in a lower portion of the external electrode with a bottom protruding from a lower end of the external electrode. An oxygen concentration cell is formed from the bottomed solid electrolyte and a standard electrode provided in the solid electrolyte, and oxygen in the molten metal is generated by an electromotive force generated between the external electrode and the standard electrode based on an electrochemical principle. An oxygen probe for measuring the concentration is provided.

Further, it is formed of a cylindrical non-porous body that does not allow the molten metal to pass therethrough, and is attached to at least the outer periphery of an external electrode immersed in the molten metal except for the bottom of the oxygen probe to protect the outer periphery of the oxygen probe. The lower end protruded from the lower end of the external electrode, at the time of immersion, leaving a gas between the bottom of the solid electrolyte protruding from the lower end of the external electrode and forming a dent that cuts off the contact between the molten metal and the fixing agent, An inner protective tube that ensures that the lower end of the inner protective tube does not exceed the height of the bottom of the solid electrolyte to ensure contact between the bottom of the solid electrolyte and the molten metal, and a slag in the molten metal that is permeable to the molten metal but It is made of a bottomed porous material that blocks the permeation of oxygen, and is mounted on the outer periphery of the inner protective tube from the bottom of the oxygen probe to protect the oxygen probe. Forming a space between the bottom of the probe, in which a external protective tube as the molten metal that has passed through the outer protective tube accumulates in the immersion time within the gap.

According to a second aspect of the present invention, there is provided an apparatus for measuring the concentration of oxygen in molten metal according to the first aspect, wherein a notch is provided in a part of a non-porous inner protective tube, and a porous body covering the notch is protected externally. The molten metal that has passed through the tube is brought into contact with the external electrode through the cutout. The notch may be provided on a part of the outer periphery of the inner protective tube, or may be provided on the entire periphery of the inner protective tube so that the inner protective tube is divided into two parts in the axial direction.

According to a third aspect of the present invention, the apparatus for measuring the concentration of oxygen in molten metal has a non-porous internal protective tube and a porous external protective tube made of ceramics having particularly excellent heat resistance.

When a protective tube is attached to the oxygen probe as in the first invention, when the oxygen probe is immersed in the molten metal, the molten metal flow does not directly hit the solid electrolyte due to the action of the protective tube, so rapid heat conduction occurs. And cracks and breakage due to thermal shock of the solid electrolyte can be effectively prevented. In addition, since the outer protective tube is formed of a porous body, the molten metal permeates the porous body, and thereby slag existing in the molten metal is adsorbed and removed, thereby effectively preventing slag from adhering to the solid electrolyte. be able to. Furthermore, the inner protective tube is made of a non-porous body, the lower part of which is protruded from the lower end of the external electrode to form a dent on the outer periphery of the bottom of the solid electrolyte. As we tried to avoid contact with the fixative,
The electromotive force can be measured with high durability for a long time and with high precision without reaction deterioration of the fixing agent and erosion of the solid electrolyte due to the influence. Further, since the projecting amount of the lower end of the inner protective tube is suppressed so as not to exceed the height of the bottom of the solid electrolyte, the contact between the solid electrolyte and the molten metal can be ensured.

When a notch is provided in a part of the inner protective tube as in the second invention, even if the inner protective tube is a non-porous body through which molten metal does not permeate, the porous outer protective tube can be used. Since the permeated molten metal can be brought into contact with the external electrode through the notch, the formation of the oxygen concentration cell can be easily maintained.

According to the third aspect, since the protection tube is made of ceramic, cracks and breakage due to thermal shock of the solid electrolyte can be more effectively prevented.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the apparatus for measuring the oxygen concentration in a molten metal according to the present invention will be described below with reference to the longitudinal sectional view shown in FIG. In FIG. 1, an oxygen probe 1 is the same as that shown in FIG. 2, and has a bottomed crucible-shaped solid electrolyte 2, a lead wire 3, a metal-metal oxide standard electrode 5,
It comprises a cylindrical external electrode 6 and a fixing agent 7 for fixing the solid electrolyte 2 to the external electrode 6.

In the embodiment of the present invention, a protective tube 4 for protecting the oxygen probe 1 is further mounted on the oxygen probe 1. The protective tube 4 has an inner protective tube 10 made of a ceramic non-porous body that does not allow the molten metal 8 to pass through, and an outer protective tube 10 made of a ceramic porous body that allows the molten metal 8 to pass through but prevents the slag in the molten metal from passing through. And a protection tube 11.

The inner protective tube 10 is a tubular body that is opened up and down, and is mounted on the external electrode 6 of the oxygen probe 1 to protect the outer periphery of the oxygen probe 1. The mounting position on the external electrode 6 is an outer peripheral portion immersed in at least the molten metal 8 except for the bottom 1 a of the oxygen probe. The lower end 10a of the inner protective tube attached to the outer electrode 6 protrudes downward by a certain amount from the lower end 6a of the outer electrode. A fixing agent 7 for fixing the solid electrolyte 2 in the open lower portion of the external electrode 6 between the protruding lower end 10a of the inner protective tube and the bottom 2a of the solid electrolyte also protruding from the lower end 6a of the external electrode 6. A concave 12 having a lower surface 7a as a bottom surface is formed, and a gas 14 is confined and retained in the concave 12 during immersion so that the contact between the molten metal 8 and the fixing agent 7 is cut off. The protruding amount of the lower end 10a of the inner protective tube is set to a value that does not exceed the height of the solid electrolyte bottom 2a in order to secure contact between the bottom 2a of the crucible-shaped solid electrolyte and the molten metal 8 accumulated in the oxygen probe bottom 1a.

When the outer periphery of the outer electrode 6 at the portion immersed in the molten metal 8 is mounted by the non-porous inner protective tube 10, the outer electrode 6 does not come into contact with the molten metal 8. Is provided with an annular notch 13 at a part thereof, and the molten metal 8 penetrating through the porous outer protective tube 11 is provided.
However, it is configured to contact the external electrode 6 through the cutout 13.

The outer protective tube 11 is a bottomed cylindrical body whose upper part is open and whose lower part is closed, and like the inner protective tube 10, to protect the oxygen probe 1,
From a, it is mounted on the outer circumference of the inner protective tube 10 mounted on the outer circumference of the external electrode 6. The portion where the outer protective tube 11 and the inner protective tube 10 overlap is brought into close contact, but a gap 15 is provided between the bottom 11a of the outer protective tube and the bottom 1a of the oxygen probe 1.
Is formed so that the molten metal 8 that has passed through the outer protective tube 11 made of a porous body is accumulated in the gap 15 during immersion.

Here, as the material of the ceramic porous body and the non-porous body, a compound having good heat resistance, for example, Al
₂ O ₃ , ZrO ₂ , SiC, Al ₂ TiO ₅ , MgO,
It is appropriately selected in consideration of reactivity with a molten metal such as TiO ₂ , Si ₃ N ₄ and SiO ₂ , heat resistance at a melting temperature, and repetitive thermal shock resistance during use. Especially in the case of a porous body,
In addition to these, consideration is given to manufacturing problems such as workability into a porous body, in addition to its permeability.

Next, the operation of the oxygen concentration measuring device having the above configuration will be described. A portion of the oxygen probe 1 inserted into the molten metal 8 is protected by an inner protection tube 10 and an outer protection tube 11 made of heat-resistant ceramic. Therefore, when the oxygen concentration measuring device is inserted into the molten metal 8 or when the measurement is completed,
Mechanical to the solid electrolyte 2 that occurs when the
Thermal shock can be reduced, and the destruction and cracking of the solid electrolyte 2 can be effectively prevented. Further, even if the molten metal 8 to be inserted has a flow, the solid electrolyte 2 is immersed in the molten metal pool without flow in the space 15 surrounded by the external protective tube 11, so that the impact is further reduced. It can withstand long-term use.

The molten metal 8 coming into contact with the solid electrolyte 2 of the oxygen probe 1 is filtered by an external protective tube 11 made of a porous material to remove slag in the molten metal 8, so that an oxygen concentration measuring device is inserted. When pulling up, the slag does not come into contact with the solid electrolyte 2 of the oxygen probe 1. For this reason, an electromotive force is not generated by mistake due to the contact of the slag, and accurate concentration measurement can be performed.

Further, since a recess 12 surrounded by the lower end 10a of the inner protective tube and the bottom 2a of the solid electrolyte is formed in the bottom 1a of the oxygen probe 1, it is formed by the outer protective tube 11 and the bottom 1a of the oxygen probe. When the molten metal 8 flows through the outer protective tube 11 and flows into the gap 15, the gap 15
Most of the gas inside is evacuated to the outside.
Only the gas inside is trapped and remains. Therefore,
Since the contact between the fixing agent 7 fixing the solid electrolyte 2 to the external electrode 6 and the molten metal 8 is avoided, the reaction deterioration due to the contact with the molten metal 8 does not occur, and the solid electrolyte 2 is affected by the reaction deterioration. It will not be affected or affect the electromotive force value.

The contact between the solid electrolyte bottom 2a and the molten metal 8 is ensured by adjusting the amount of protrusion of the lower end 10a of the inner protective tube, and the contact between the external electrode 6 and the molten metal 8 is Notch 1 provided in internal protective tube 10
3, the formation of the oxygen concentration cell is not hindered even if the protective tubes 10 and 11 are attached to the oxygen probe 1.

In order to mount the protective tubes 10 and 11 on the oxygen probe 1, first, two internal protective tubes 10 are prepared.
After fitting the wire at a predetermined position above the cylindrical external electrode 6,
Notch 1 for maintaining contact between external electrode 6 and molten metal 8
The second wire is fitted with an interval corresponding to 3 and fixed with a ceramic adhesive. When the second inner protective tube 10 is fitted, the amount of protrusion of the lower end 10a of the inner protective tube from the lower end 6a of the external electrode is particularly important as described above, and the contact between the molten metal 8 and the solid electrolyte 2 is ensured. However, the contact between the fixing agent 7 and the molten metal 8 is determined to be avoided. Thereafter, the gap between the two internal protective tubes 10 and 10 (notch 1
The external protective tube 11 is fitted so that 3) is covered, and is fixed with a ceramic adhesive, and the mounting is completed. Note that the inner protection tube 10 and the outer protection tube 11 may be bonded in advance, and the integrated one may be fitted to the outer electrode 6.

[0031]

According to the first aspect of the present invention, when the oxygen probe is immersed in the molten metal, the rapid thermal conduction is reduced by the action of the protective tube for relaxing the thermal conduction, and the heat of the solid electrolyte is reduced. Cracks and breakage due to impact can be effectively prevented. Further, since the slag existing in the molten metal is adsorbed and removed by the molten metal penetrating through the external protective tube of the porous body, it is possible to effectively prevent the slag from adhering to the solid electrolyte. Further, it is possible to effectively prevent the reaction between the molten metal and the fixing agent due to the residual gas trapped in the recess. As a result, no abnormal electromotive force is generated, and the oxygen concentration in the molten metal can be measured stably with high durability for a long time with high accuracy.

According to the second aspect of the present invention, the cut-out portion is provided in the non-porous internal protective tube, and even if the non-porous internal protective tube is attached to the external electrode, the external electrode can be removed. And molten metal can be kept in contact.

According to the third aspect of the present invention, since the protective tube is made of ceramic, cracks and breakage due to thermal shock of the solid electrolyte can be more effectively prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an apparatus for measuring an oxygen concentration in a molten metal according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a conventional apparatus for measuring oxygen concentration in molten metal.

[Explanation of symbols]

 Reference Signs List 1 oxygen probe 1a bottom of oxygen probe 2 solid electrolyte 2a bottom of solid electrolyte 5 standard electrode 6 external electrode 6a lower end of external electrode 7 fixing agent 7a lower surface of fixing agent 8 molten metal 10 internal protection tube 10a lower end of internal protection tube 11 external Protection tube 11a Bottom portion of external protection tube 12 Depression 13 Notch 14 Gas 15 Void

Continued on the front page (72) Inventor Daisuke Ikeda 4-10-1, Kawajiri-cho, Hitachi City, Ibaraki Prefecture Inside the Toyoura Plant of Hitachi Cable Co., Ltd. (72) Inventor Kunio Hashimoto 4-1-1, Kawajiri-cho, Hitachi City, Hitachi, Hitachi (72) Inventor Kohei Naito 4-10-1 Kawajiri-cho, Hitachi City, Ibaraki Pref. Hitachi Cable Co., Ltd.

Claims (3)

[Claims] An external electrode having a cylindrical shape, a solid electrolyte with a bottom fixed in a lower part of the external electrode with a fixing agent and a bottom protruding from a lower end of the external electrode, and a standard electrode provided in the solid electrolyte. An oxygen probe that forms an oxygen concentration cell from the above, measures the oxygen concentration in the molten metal by the electromotive force generated between the external electrode and the standard electrode based on the electrochemical principle, and a cylindrical non-porous body that does not allow the molten metal to pass In order to protect the outer periphery of the oxygen probe, it is attached to the outer periphery of the external electrode immersed in at least the molten metal except for the bottom of the oxygen probe, and the attached lower end protrudes from the lower end of the external electrode. A gas is left between the bottom of the solid electrolyte protruding from the lower end of the electrode to form a recess that cuts off the contact between the molten metal and the fixing agent, and the amount of protrusion of the lower end of the inner protective tube increases the height of the bottom of the solid electrolyte. Over An inner protective tube that ensures the contact between the bottom of the solid electrolyte and the molten metal, and a bottomed porous body that allows the molten metal to pass through but blocks the slag in the molten metal to protect the oxygen probe The oxygen probe is mounted on the outer periphery of the inner protection tube from the bottom of the oxygen probe so that a gap is formed between the bottom of the attached outer protection tube and the bottom of the oxygen probe. And an external protective tube configured to store the molten metal that has passed through the apparatus. 2. A notch is provided in a part of the inner protective tube of the non-porous body, and molten metal that has passed through the outer protective tube of the porous body covering the notch contacts the external electrode through the notch. The apparatus for measuring the oxygen concentration in a molten metal according to claim 1. 3. The apparatus for measuring the oxygen concentration in a molten metal according to claim 1, wherein the non-porous internal protective tube and the porous external protective tube are both made of ceramic.