JP3293041B2 - Apparatus for measuring oxygen activity in slag, consumable crucible used for the measuring apparatus, and temperature measuring method applied to the measuring apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved technique for measuring oxygen activity in slag which can measure oxygen activity in hot metal slag or molten steel slag generated in an iron making process with high accuracy. Is to improve the efficiency and accuracy of measurement work by providing calibration materials that are easy to handle and have stable chemical properties, and to measure oxygen activity by reducing the cost of consumable crucibles. The present invention relates to a technique capable of improving the accuracy of temperature control in a crucible and the accuracy of measuring oxygen activity by reducing the cost and further proposing a method for quickly and accurately measuring the temperature in an iron crucible.

[0002]

2. Description of the Related Art Steelmaking slag is not only indispensable as an existence for isolating molten steel from the atmosphere, but also because steelmaking slag exists in a suspended state on molten steel and comes into contact with molten steel to form a chemical reaction. And indirectly governs the chemical reaction of the molten steel itself. Therefore, in order to adjust the composition of molten steel as a product, it is inevitably important to control the slag composition. However, in order to estimate the degree of chemical reaction between molten steel and slag, it is not enough to know the composition of the slag, and it is very important to know the oxygen activity in the slag.

As an apparatus for measuring oxygen activity in slag, there are those proposed by the present applicant as Japanese Patent Application Nos. 1-271033, 3-5141 and 3-181948. For example,
In the apparatus proposed in Japanese Patent Application No. 1-271033, as shown in FIG. 8, a reaction tube b filled with an inert gas is vertically provided in a condensing type heating furnace a, and a heating section in the reaction tube b is provided. An iron crucible c as shown in FIG. 8 is detachably mounted on a metal mantle tube d also serving as a support, and a thermocouple e for temperature measurement is provided in the mantle tube d. The temperature sensing part is arranged in a state of being close to the lower surface of the iron crucible c.
Inside, a specific metal M which does not form an alloy with iron at least under an inert atmosphere and hardly generates an oxide and has a specific gravity heavier than the slag S is accommodated in a molten state together with the slag S to be measured. I have. At the time of the measurement, the solid electrolyte f in which the standard electrode is provided in the specific metal M and the slag S which are brought into a molten state by heating the condensing type heating furnace a.
Is immersed, and the electromotive force between the iron crucible c also serving as a control electrode and the standard electrode is measured by a meter g to obtain a slag S.
Was actually measured.

The oxygen activity measurement of steelmaking slag by this apparatus is, in other words, an equilibrium oxygen partial pressure measurement of iron-slag reaction, which is a very important factor in considering the equilibrium reaction between molten steel and slag in the steelmaking process. The iron oxide activity in a certain slag can be measured. This depends on the following method. First, iron oxide (FeO) in the collected sample slag
₍ Eq. 1) is used as an equilibrium reaction equation between _{(in slag)} ) and solid iron (Fe _(S) ) of an iron crucible.

(Equation 1) The activity of iron oxide is indicated by the partial pressure of oxygen in "Equation 1". That is, with respect to the equilibrium oxygen partial pressure (P ° O ₂ (Fe + FeO _PURE )) of solid iron and pure iron oxide (FeOpure), the equilibrium oxygen of iron oxide (FeO in slag) in solid iron and measurement slag is The ratio “Equation 2” of the partial pressure (P ° O ₂ (Fe + FeO in slag)) is obtained as the iron oxide activity in the slag.

(Equation 2) In this device, oxygen concentration battery (solid electrolyte)
Thus, the equilibrium oxygen partial pressure of solid iron and pure iron oxide is measured, and the iron oxide activity of the slag can be obtained by measuring the equilibrium oxygen partial pressure of the slag for which the iron oxide activity is to be determined. By knowing the iron oxide activity in the slag in this way, it has become possible to infer a reaction of phosphorus or sulfur which is not very desirable for products.

[0005] The present applicant has filed the same application (Japanese Patent Application No. 1-271033).
No.) also mentions other ideas for each part of the device. For example, in this device, the temperature of the crucible is constantly monitored by a temperature measuring means constituted by a thermocouple e and a meter h arranged below the iron crucible, and the temperature is collected so that the temperature inside the iron crucible is maintained at a predetermined temperature. Although the power supply to the heat source of the optical heating furnace is controlled, the present applicant discards the iron crucible c used in this device at the end of each measurement in order to avoid contamination with impurities other than the sample to be measured. The idea is to use a so-called consumable iron crucible, and as a specific configuration, by melting and solidifying a specific metal inside the consumable crucible in advance, to accommodate the specific metal at each measurement operation. It was suggested that this would not be necessary, and that this would help to avoid forgetting to insert a specific metal and promote the efficiency of measurement work.

In order to maintain the accuracy of the measurement of the oxygen activity by the apparatus, a substance whose oxygen activity is known is used as a calibration substance, and this calibration substance is periodically inserted into an iron crucible instead of slag. He also proposed calibrating the instruments.

The apparatus for measuring oxygen activity in slag proposed in Japanese Utility Model Application No. 3-5141 is a further embodiment of the above apparatus, and the structure thereof is based on the above structure as shown in FIG. , The iron crucible c is covered with the transparent tube i, the mantle tube d is covered with the opaque quartz tube j, and the exhaust pipe k is erected above the iron crucible c. It was possible to prevent it.

Further, Japanese Patent Application No. 3-181948 discloses that, as shown in FIG. 10, a portion close to the iron crucible c on the surface of the mantle tube d surrounding the thermocouple e arranged on the lower surface of the iron crucible c, as compared with the other portions. Also, the responsiveness of the thermocouple e was improved by providing the colored portion m having a high heat absorption rate.

[0009]

However, such an apparatus for measuring the oxygen activity in slag has the following problems. First, there is a problem that handling of the calibration substance is troublesome. That is, in Japanese Patent Application No. 1-271033, as a calibration substance, ferrous oxide alone or a mixture of ferrous oxide and a halide of an alkaline earth metal and / or a halide of an alkali metal, for example, calcium fluoride (CaF ₂ ) and calcium chloride (CaCl ₂ ) have been proposed to use a mixture thereof. However, since these substances have a high water absorption, their chemical properties are liable to be deteriorated and handling is troublesome. The production of highly toxic gas such as gas also involved danger in handling. In addition, there was a difference between the measurement value of the steelmaking slag to be measured and the measurement level of the calibration sample, which was not very practical. When corresponding to the actual operation slag component, the content of calcium fluoride (CaF ₂ ) and calcium chloride (CaCl ₂ ) is extremely small, and the content of such calcium (CaF ₂ ) and calcium chloride (CaCl ₂ ) Calibration substances with a high ratio have a problem because they are separated from the slag components in the actual operation.

[0010] As a second problem, there is a problem that the production cost of the consumable crucible is high. That is, Japanese Patent Application No. 1-27.
In the technology described in No. 1033, from the viewpoint of improving the efficiency of measurement work, a consumable crucible in which a specific metal is melted and solidified in advance is used on the inner surface of the crucible, but an atmosphere furnace is used to melt and solidify the specific metal without oxidizing it. In addition, it is difficult to set the conditions described above, and it is necessary to operate a heating furnace for melting, so that many costs are required, and the iron crucible cannot be provided at a cost suitable for a consumable crucible.

Further, as a third problem, there is a limit to the accuracy of temperature measurement, and it is difficult to further improve the accuracy of oxygen activity measurement. Also, since the response is low, it is difficult to accurately measure the crucible temperature that changes every moment. could not. In order to improve the measurement accuracy of the oxygen activity, it is necessary to control the temperature of the slag to be measured with high accuracy. In the technique described in Japanese Patent Application No. 1-271033, the temperature of the iron crucible c is measured by the temperature measuring element e positioned below the iron crucible. The measurement accuracy achieved by this measuring method is, for example, ± 5 at 1400 ° C. ° C, and it was difficult to further improve the measurement accuracy. Japanese Patent Application No. 3-181948 discloses a temperature measuring element e.
The responsiveness of the temperature measuring element e can be increased to some extent by providing a colored portion having a higher heat absorption rate than the other portions at a position close to the iron crucible c on the surface of the mantle tube surrounding the outer tube, but it is still possible. It was not enough. To measure the temperature of the slag most accurately, the temperature inside the iron crucible may be measured directly.However, for this purpose, it is necessary to insert a temperature measuring element from above the iron crucible and place it at a predetermined depth inside the iron crucible. There is a problem in workability. Further, when a thermocouple temperature measuring element is used, a new thermocouple must be prepared for each measurement, and there is a problem that a large amount of cost is required for one measurement. Further, the thermocouple temperature measuring element is provided with a quartz protective tube or the like for the purpose of protecting the hot junction, and thus has a problem of poor response.

The present invention has been made in view of such a situation, and solves the above three problems included in the apparatus for measuring oxygen activity in slag proposed by the present applicant as Japanese Patent Application No. 1-271033. In particular, we propose a new calibration material that is easy to handle and has high calibration accuracy, and an inexpensive consumable crucible that contains a specific metal. It is also intended to provide a temperature measuring method that can be easily measured.

[0013]

Means for Solving the Problems Among the above-mentioned problems, the first invention aimed at improving the handleability of the calibration substance is described below.
It is characterized in that a mixture of steelmaking slag components containing at least ferrous oxide is used as a calibration substance. As steelmaking slag components used together with ferrous oxide, silicon dioxide (SiO ₂ ), calcium oxide (CaO), aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO),
Manganese oxide (MnO), phosphorus pentoxide (P ₂ O _5), sodium oxide (Na ₂ O), titanium oxide (TiO _2), chromium oxide (Cr ₂ O _3), nickel oxide (NiO), barium oxide (BaO ) Or boron oxide (B ₂ O ₃ ).
In addition, depending on the state of the steel slag to be measured, a trace amount of one or both of calcium fluoride (CaF ₂ ) and calcium chloride (CaCl ₂ ) may be added in addition to the above to bring the component closer to the steel slag to be measured. Is sometimes preferred. If calcium fluoride (CaF ₂ ) and calcium chloride (CaCl ₂ ) are contained in large proportions, the water absorption is high, so the chemical properties may not be stable or highly toxic gas may be generated. There is no such problem. Although silicon is a metalloid element, silicon dioxide is treated here as a metal oxide.

A second invention aimed at reducing the cost of the consumable crucible is to provide a consumable crucible by pressing a specific metal powder, wire or plate into the inner surface of the iron crucible in such a manner that the powder, wire or plate cannot be dropped from the iron crucible. It is characterized by comprising a crucible.

[0015] Furthermore, a third invention aimed at providing a highly accurate and simple method of measuring the temperature in an iron crucible is a metal or a conductive material which does not form an alloy with a specific metal or slag and does not melt under measurement temperature conditions. The tip of the ceramic wire, rod or plate is brought into contact with the inner surface of the iron crucible, and the thermoelectromotive force between the iron crucible and the metal is measured. It is characterized in that the temperature in the iron crucible is measured by substituting into a relational expression.

[0016]

The measurement of the oxygen activity in the slag using the present measuring device is performed as follows. First, a specific metal, which is a metal that does not form an alloy with iron and hardly generates an oxide at least under an inert atmosphere, is pushed into an iron crucible in advance and placed therein, and a slag to be measured is put thereon. Next, the iron crucible is housed in a melting furnace filled with an inert gas, and the iron crucible is heated to melt the slag and the specific metal. Subsequently, the solid electrolyte of one end closed tube type containing the standard electrode is passed through the slag layer in a molten state and immersed in a specific metal,
The oxygen activity in the specific metal is measured by measuring the electromotive force between the iron crucible also serving as the control electrode and the standard electrode, and the oxygen activity in the slag is determined from this value.

When measuring the electromotive force between the iron crucible also serving as the reference electrode and the standard electrode, the temperature inside the iron crucible is also measured at the same time. This measurement is performed as follows. That is, a metal that does not form an alloy with the specific metal and does not melt during the measurement time, such as a wire, a rod or a plate, such as molybdenum or tungsten, is inserted from above the iron crucible, and the tip of the metal body is iron crucible. Touch the bottom. For example, when a molybdenum rod is used, the molybdenum rod and the iron crucible are equivalent to a thermocouple having a hot junction at a contact portion between the molybdenum rod and the iron crucible. A thermoelectromotive force is generated between them. Then, the temperature of the hot junction is measured by substituting the measurement result of the thermoelectromotive force into a previously obtained relational expression between the thermoelectromotive force and the temperature.

The temperature measurement is preferably carried out simultaneously with the measurement of the oxygen activity in the slag. For this reason, the timing of inserting a metal body such as a molybdenum rod is most preferably carried out almost at the same time as the insertion of a solid electrolyte of a closed-tube type. Even when it is difficult to simultaneously insert the solid electrolyte and the metal rod, it is preferable that the insertion timing of the solid electrolyte and the insertion timing of the metal rod be as close as possible.

In addition, a calibrator prepared by mixing ferrous oxide and another metal oxide is used for calibrating an instrument to maintain the measurement accuracy of the present apparatus. Since these mixtures do not contain or contain halides, the amount thereof is extremely small as in actual operation slag, so that no toxic gas is generated and the water absorption is low, so that handling is extremely easy, and Calibration accuracy is extremely high because the chemical properties are stable.

[0020]

Next, details of the present invention will be described based on embodiments. The first invention is characterized in that the apparatus for measuring oxygen activity in slag described above uses a mixture of steelmaking slag components containing at least ferrous oxide as a calibration substance.

Metal oxides used together with ferrous oxide include silicon dioxide (SiO ₂ ) and calcium oxide (Ca
O), aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), manganese oxide (MnO), phosphorus pentoxide (P ₂ O ₅ ), sodium oxide (Na ₂ O), titanium oxide (TiO ₂ ), oxidation One or more selected from chromium (Cr ₂ O ₃ ), nickel oxide (NiO), barium oxide (BaO), and boron oxide (B ₂ O ₃ ) can be employed. In addition, depending on the condition of the steelmaking slag to be measured, a small amount of calcium fluoride (C
In some cases, it may be preferable to add one or both of aF ₂ ) and calcium chloride (CaCl ₂ ) to make it closer to the component of the steelmaking slag to be measured. As a matter of course, the calibration substance needs to show a stable oxygen activity with respect to a temperature change, and the mixing ratio is determined on the assumption that such a condition is satisfied.

According to the procedure for determining the mixing ratio employed in the embodiment of the present invention in order to obtain a calibration sample satisfying the above conditions, a calibration material consisting of a mixture of three kinds of substances, ferrous oxide, calcium oxide and silicon dioxide, is prepared. A case will be described as an example. The reason for selecting a mixture of three types of materials, ferrous oxide, calcium oxide, and silicon dioxide, as the calibration sample is that these three types of materials are the most basic components in steelmaking slag. This is because the element of basicity, which is the ratio of calcium to silicon dioxide, is treated as a very important index. Here, the handling of the oxygen activity here has the same value as the iron oxide activity in the slag as described above. This is slag in the steelmaking field.
This is because the iron oxide activity is a meaningful numerical value in the analysis of the molten steel reaction, and clearly shows its suitability as a calibration material.

FIG. 1A is an isothermal sectional view of a ternary system of ferrous oxide, calcium oxide and silicon dioxide at 1673K. 1673K is the temperature when measuring the oxygen activity. The calcium oxide and the silicon dioxide are preliminarily mixed so that the molar ratio is 3: 1 so as to be located at the point A on the isothermal cross-sectional view, and then the oxidized oxide is drawn on the line connecting the points A and D. While mixing while changing the ratio of ferrous iron, various mixed samples having different concentration ratios (molar fractions) of ferrous oxide are prepared. FIG. 2 shows the results of measuring the iron oxide activity of various calibration samples having different concentrations of ferrous oxide using the oxygen activity measuring device in the present slag. The concentration ratio of iron (FeO) (XFe0) is shown, and the vertical axis shows the activity (aFe0) of ferrous oxide (FeO). In this measurement, silver is used as the specific metal. The pure silver at this time serves as a lead wire by directly contacting the solid electrolyte, and is necessary for performing stable electromotive force measurement. Also, by equilibrating with the sample slag in the iron crucible, it becomes possible to measure the oxygen activity in the slag.

The point D in FIG. 1 indicates that CaO and SiO ₂
Indicates that the sample is a slag sample in which all are FeO. The results of measuring the iron oxide activity of this slag sample are as follows: pure iron oxide (FeO) and solid iron (Fe).
And the value is 1. This value is shown in FIG.
, The size of D '. D 'in FIG.
The region from C ′ to C ′ indicates that CaO, SiO ₂ , and FeO are in a liquid state (liquid phase: L). The region from C ′ to B ′ is a two-phase coexistence region of the compound 2CaO · SiO ₂ and the liquid phase (L). The area from B 'to A' is 2
This indicates that the three-phase coexistence region of CaO.SiO ₂ , 3CaO.SiO ₂ and the liquid phase (L). FIG. 2 shows, as described above, the iron oxide (F) on the line connecting points A and D in FIG.
eO) The concentration is shown on the horizontal axis, and the vertical axis shows the activity value of FeO. As a sample used as a standard sample, a sample having a composition such that the activity value is constant, for example, in a region E, was used. Within this range, the activity value of iron oxide is stable even if there is some variation in the concentration ratio of ferrous oxide, so that it is suitable for use as a calibration sample. In addition, before an abrupt change in the activity value occurs as in the region F, in other words, C ′
The sample in the region where the activity change is small before the activity concentration becomes almost saturated as indicated by the dot, the activity value of the iron oxide is small even if there is some fluctuation in the ferrous oxide concentration. Because it is stable, it is suitable for use as a calibration sample.

The sample prepared by such a method has a small change in iron oxide activity, that is, shows a stable oxygen activity, and thus is suitable for use as a standard sample for calibration. Moreover, since these mixtures do not contain halides, no toxic gas is generated, and their water absorption is low. Therefore, their handling is extremely easy, and their chemical properties are stable, so that their calibration accuracy is extremely high. In this embodiment,
A mixture of three elements of ferrous oxide, calcium oxide and silicon dioxide has been exemplified, but silicon dioxide (SiO ₂ ), calcium oxide (CaO), aluminum oxide (Al ₂ O ₃ ),
Magnesium oxide (MgO), manganese oxide (Mn)
O), phosphorus pentoxide (P ₂ O ₅ ), sodium oxide (Na ₂
O), titanium oxide (TiO ₂ ), chromium oxide (Cr ₂ O)
₃ ), nickel oxide (NiO), barium oxide (Ba)
O), boron oxide (B ₂ O ₃ ), traces of calcium fluoride (CaF ₂ ), traces of calcium chloride (CaCl ₂ )
The mixing ratio can be determined by a similar method when one or more selected from the above are employed. Even when calcium fluoride (CaF ₂ ) and calcium chloride (CaCl ₂ ) are contained, there is no problem because their amounts are extremely small as in the case of actual operation slag.

Next, the details of the second invention will be described based on the illustrated embodiment. The second invention is characterized in that the specific metal is pushed into the inner surface of the iron crucible in a state where the specific metal cannot be dropped from the iron crucible and is installed. As a form of the specific metal to be pushed into the inner surface of the iron crucible and installed, a powdery one as shown in FIG. 3A, a linear one as shown in FIG.
As shown in (c), a plate shape or a foil shape can be adopted. Then, in order to push the specific metal of each mode into the iron crucible so as not to fall off, the specific metal is repeatedly pressed by the cylindrical jig 2 as shown in the figure, and the specific metal is compression-formed or compressed by this pressing force. It is possible.

For example, when a plate-shaped specific metal is used,
It is conceivable that a specific metal having a plane area larger than the inner diameter of the iron crucible is pushed into the inner surface of the iron crucible. The present inventor studied a method of pushing a pure silver plate material having a plane area of 15 mm × 15 mm and a thickness of 1 mm into an iron crucible having an inner diameter of 16 mm, and as shown in FIG. 4, an outer diameter having a conical pointed tip as shown in FIG. When the plate 3 is pushed into the iron crucible using the 13 mm cylindrical jig 2a and installed, 0.5 kg is required.
It has been confirmed that any air cylinder capable of exerting a pressure of about f to 9.8 kgf / cm ² can be sufficiently used as a driving source for pressurization. It is also possible to use a plurality of plate members to be pushed into the iron crucible, and in this case, the amount of pure silver used can be saved by selecting the number of pure silver plates as needed. In addition, since the push-in installation can be easily performed by the pressing force of the air cylinder as described above, there is no need to operate a heating furnace as in the case of melting and solidifying a specific metal in an iron crucible, thereby reducing the cost of a consumable crucible. Can contribute.

Next, the details of the third invention will be described based on embodiments. A third invention aimed at providing a method capable of easily and accurately measuring the temperature in an iron crucible is a wire or rod made of a metal or a conductive ceramic which does not form an alloy with a specific metal and slag on the inner surface of the iron crucible. Or by contacting the tip of the plate, measure the thermoelectromotive force between the iron crucible and the metal,
The temperature in the iron crucible is measured by substituting the measurement result into a relational expression between the electromotive force and the temperature, which is obtained in advance. FIG. 5 shows an embodiment of the third invention, in which an iron crucible c in a heated state is omitted from surrounding devices. The metal rod 4 is inserted into the iron crucible c containing the slag S and the specific metal M that have been heated to a molten state, and the tip of the metal rod 4 is brought into contact with the bottom of the iron crucible. An instrument 5 for measuring thermoelectromotive force is connected between the upper end of the metal rod and the iron crucible c, and the upper end of the metal rod is maintained at room temperature. As the material of the metal rod 4, a material that does not melt under a measurement temperature environment and does not form an alloy with slag and a specific metal is used. One or more alloys selected from the above can be used. Since the lower end of the metal rod in contact with the bottom of the iron crucible has a temperature difference with respect to the upper end of the metal rod, a thermoelectromotive force is generated between the metal rod and the iron crucible by the Seebeck effect. 5, the temperature of the contact portion between the metal rod and the iron crucible is directly measured. Further, a rod made of conductive ceramics can be used instead of the metal rod. As the conductive ceramic, it is possible to use a mixture conductive ceramic which is a mixture of a metal component and a ceramic component, or a compound conductive ceramic having conductivity by itself. When using a mixed conductive ceramic, molybdenum,
Use one or more alloys selected from tungsten, niobium, rhenium, vanadium, cesium, platinum, palladium, rhodium, lanthanum, zirconium, and use zirconia, silicon carbide, silicon nitride, nitride as the ceramic component in the conductive ceramics One or a mixture of plural kinds selected from boron, lanthanum chromide or zirnium boride can be used. When compound conductive ceramics are used, one or a mixture of one or more selected from boron nitride, lanthanum amide, and zirnium boride can be used as the compound conductive ceramics.

The purpose of measuring the temperature in the iron crucible by this method is to improve the accuracy of the oxygen activity measurement in the slag by measuring the temperature in the iron crucible with high accuracy.
As shown in FIG. 6, it is preferable to perform almost simultaneously with the operation of measuring the electromotive force generated between the standard electrode 6 derived from the solid electrolyte and the iron crucible c having the function of the reference electrode by the instrument 7.

As described above, the temperature measurement is basically performed simultaneously with the measurement of the oxygen activity using the solid electrolyte. However, when a high melting point metal such as molybdenum or tungsten is used as the metal rod, these metals are made of iron. Since it can withstand a long time without melting in the crucible, the temperature change in the iron crucible may be continuously measured.

The positioning of the metal rod in the iron crucible only needs to be lowered until the tip of the metal rod inserted from above the iron crucible comes into contact with the bottom of the iron crucible, and positioning is extremely easy. In addition, since the whole is a metal rod and there is no temperature sensitive part that requires special attention in handling like a general temperature measuring element, handling is easy. In addition, this method of measuring temperature involves contacting a metal rod with an iron crucible and forming a hot junction at the contact portion itself with the iron crucible to be measured.
As in the case of a conventional temperature measuring element in which a hot junction is covered with a heat-resistant protective tube, extremely high responsiveness can be exhibited without requiring time for temperature rise. Note that, here, only the case where the present measuring method is applied to an apparatus for measuring oxygen activity in slag has been described, but it goes without saying that the present temperature measuring method can be widely applied as a temperature measuring method for a sample to be dissolved in an iron crucible. Absent.

In order to confirm the effect of the third invention, the present inventor inserted a molybdenum rod having an outer diameter of 1 mm and a length of 200 mm into the iron crucible from above the iron crucible and measured the thermoelectromotive force.
The temperature in the iron crucible was calculated from the measurement result with reference to a graph (FIG. 7) showing the relationship between the thermoelectromotive force and the temperature between the iron crucible and the molybdenum rod, which was measured and found in advance. It was confirmed that highly accurate results were obtained.

[0033]

According to the first invention, a mixture of steelmaking slag components containing at least ferrous oxide is used as a calibration substance. This calibrator is extremely easy to handle because of its low water absorption and stable chemical properties, and therefore enables high-accuracy measurement of oxygen activity without special precautions in storage and handling. In addition, this calibrator does not contain a halide, or even if it does, the amount thereof is extremely small as in the actual operation slag, so that no toxic gas is generated.

According to the second aspect of the present invention, a consumable crucible is formed by inserting a powder of a specific metal, a wire or a plate into the inner surface of the iron crucible so as not to fall off the iron crucible. Thus, there is no need to operate the heating furnace to melt and solidify the specific metal in the iron crucible, so that a consumable crucible can be provided at low cost. Moreover, since the specific metal is simply pushed into the iron crucible using an air cylinder or the like in a pressurized state, the chemical properties of the specific metal do not change,
Unlike the case where a specific metal is melted and solidified in an iron crucible, it is not necessary to strictly monitor conditions for processing.

According to a third aspect of the present invention, the tip of a wire, rod, or plate made of a metal or conductive ceramic that does not form an alloy with a specific metal or slag on the inner surface of the iron crucible and does not melt under the measurement temperature condition is placed on the inner surface of the iron crucible. The temperature was measured by measuring the electromotive force between the iron crucible and the metal and referring to a previously determined relationship between the electromotive force and the temperature to determine the temperature in the iron crucible from the measurement result. In this temperature measurement method, the contact portion between the metal rod and the iron crucible itself becomes a hot junction, so that highly accurate temperature measurement with excellent responsiveness can be easily performed. Further, the positioning of the metal rod in the iron crucible only requires lowering the metal rod inserted from above the iron crucible until the tip of the metal rod comes into contact with the bottom of the iron crucible, which is easy to handle.

[Brief description of the drawings]

FIG. 1 is an explanatory view for explaining a method of mixing a calibration substance used in the first invention, and is an isothermal sectional view in a state where three elements of ferrous oxide, silicon dioxide and calcium oxide are mixed.

FIG. 2 is a graph showing a change in activity of iron oxide when the amount of ferrous oxide is changed along a line connecting points A and D in FIG. 1;

FIG. 3 is an explanatory view of an embodiment of the second invention, wherein (a) is a case where powder is used as a specific metal, (b) is a case where a linear body is used as a specific metal, and (c) is a specific metal When a plate or foil is used as

FIG. 4 is one embodiment of the second invention, and is an explanatory view showing a state in which a silver plate is pushed into an iron crucible and installed using a cylindrical jig having a conical tip.

FIG. 5 is an explanatory view showing an example of the temperature measurement method of the third invention.

FIG. 6 shows an example of the temperature measuring method of the third invention, in which the temperature is measured simultaneously with the measurement of the electromotive force between the standard electrode derived from the solid electrolyte and the iron crucible also serving as the reference electrode. Explanatory diagram showing how you are

FIG. 7 is an example of a graph showing a relationship between a thermoelectromotive force generated between a molybdenum rod and an iron crucible and temperature.

FIG. 8 is a conceptual explanatory view of an oxygen activity measuring apparatus using a condensing type heating furnace.

FIG. 9 is an explanatory view of an oxygen activity measuring apparatus using a condensing type heating furnace.

FIG. 10 is an explanatory view of an oxygen activity measuring apparatus using a condensing type heating furnace.

[Explanation of symbols]

 a Concentrated heating furnace b Reaction tube c Iron crucible d Mantle tube e Thermocouple f Solid electrolyte g Meter h Meter i Transparent tube j Opaque quartz tube S Slug M Specific metal 1a Powder specific metal 1b Linear specific metal 1c Plate-shaped specific metal 2 Cylindrical jig 3 Plate 4 Metal rod 5 Instrument 6 Standard electrode 7 Instrument

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Ryuji Fujiwara 1-9-9 Nagaodai, Hirakata-shi, Osaka (56) References Materials and Processes, Japan, September 3, 1990, Vol. 3, No. 4, 1087 Metal Trans B, United States, August 18, 1992, Vol. 23B, No. 4,459-466 (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 27/411 JICST file (JOIS)

Claims (7)

(57) [Claims] 1. An iron crucible is housed in a melting furnace filled with an inert gas. The iron crucible is made of a metal that does not form an alloy with iron and that does not easily generate an oxide at least under an inert atmosphere. The specific metal having a specific gravity heavier than the slag is housed in a molten state together with the slag to be measured, and a solid electrolyte of one end closed type having a standard electrode therein is immersed in the specific metal, and also serves as a control electrode. In the oxygen activity measuring device in the slag which measures the electromotive force between the iron crucible and the standard electrode, a mixture of steelmaking slag components containing at least ferrous oxide as a substance for calibrating the accuracy of the oxygen activity measurement A device for measuring oxygen activity in slag, characterized by using: 2. Steelmaking slag components used together with ferrous oxide include silicon dioxide (SiO ₂ ) and calcium oxide (C).
aO), aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), manganese oxide (MnO), phosphorus pentoxide (P ₂ O ₅ ), sodium oxide (Na ₂ O), titanium oxide (TiO ₂ ), oxidation chromium (Cr ₂ O _3), nickel oxide (NiO), barium oxide (BaO) or formed by employing the selected one or more from among boron oxide (B ₂ O ₃₎ according to claim 1, wherein in the slag of Oxygen activity measurement device. 3. A steelmaking slag component used together with ferrous oxide in addition to the steelmaking slag component according to claim 2, in addition to trace amounts of calcium fluoride (CaF ₂ ) and calcium chloride (Ca).
_{2. The} apparatus for measuring oxygen activity in slag according to claim 1, wherein one or both of Cl _{2 and} Cl ₂ are added. 4. An iron crucible is housed in a melting furnace filled with an inert gas. The iron crucible is made of a metal which does not form an alloy with iron and hardly generates an oxide under an inert atmosphere. The specific metal having a specific gravity heavier than the slag is housed in a molten state together with the slag to be measured, and a solid electrolyte of one end closed type having a standard electrode therein is immersed in the specific metal, and also serves as a control electrode. In the oxygen activity measuring device in the slag which measures the electromotive force between the iron crucible and the standard pole, the powder, the wire or the plate of the specific metal cannot be dropped from the iron crucible on the inner surface of the iron crucible. A consumable iron crucible for use in an apparatus for measuring oxygen activity in slag, wherein the iron crucible is installed by being pushed in. 5. An iron crucible is housed in a melting furnace filled with an inert gas. The iron crucible is made of a metal that does not form an alloy with iron and that does not easily generate an oxide at least under an inert atmosphere. The specific metal having a specific gravity heavier than the slag is housed in a molten state together with the slag to be measured, and a solid electrolyte of one end closed type having a standard electrode therein is immersed in the specific metal, and also serves as a control electrode. In a device for measuring oxygen activity in slag by measuring an electromotive force between an iron crucible and the standard electrode, a metal or conductive ceramic wire that does not form an alloy with a specific metal or slag and does not melt under measurement temperature conditions , The tip of the rod or plate is brought into contact with the inner surface of the iron crucible, the thermoelectromotive force between the iron crucible and the metal is measured, and this measurement result is substituted into the previously obtained relational expression between thermoelectromotive force and temperature. You Temperature measuring method applied to oxygen activity measuring device in the slag formed by measuring the temperature of the iron crucible by. 6. A metal selected from the group consisting of molybdenum, tungsten, niobium, rhenium, vanadium, cesium, platinum, palladium, and rhodium as a metal constituting a wire, a rod or a plate directly contacting the inner surface of the iron crucible, or The temperature measuring method applied to the apparatus for measuring oxygen activity in slag according to claim 5, wherein a plurality of types of alloys are used. 7. As a conductive ceramic constituting a wire, a rod or a plate directly contacting the inner surface of the iron crucible,
Use a mixture conductive ceramics which is a mixture of a metal component and a ceramic component or a compound conductive ceramic having conductivity by itself, and when using a mixture conductive ceramics, as a metal component, molybdenum, tungsten, niobium, rhenium, vanadium , Cesium, platinum, palladium, rhodium, lanthanum, using one or more alloys selected from zirconium, zirconia, silicon carbide, silicon nitride, boron nitride, lanthanum amide or boron as the ceramic component in the conductive ceramic Using one or a mixture of a plurality of kinds selected from zirnium boride, while using compound conductive ceramics, as compound conductive ceramics, boron nitride, lanthanum chromide or zirconium boride How temperature measuring applied to oxygen activity measuring device in the slag according to claim 5, wherein comprising using a mixture of several.