JPH03128453A - Component concentration sensor for molten metal by using composite solid electrolyte - Google Patents

Abstract

PURPOSE:To make measurement with high accuracy by using the composite solid electrolyte formed by using partially stabilized zirconia of magnesium oxide as the base body of the solid electrolyte and integrating a mixture composed of an oxygen ion conductor and an oxide contg. components to be measured on the base body. CONSTITUTION:The powder mixture A (metal+metal oxide), such as Mo+MoO2, Cr+Cr2O3, Fe+FeO, or Ni+NiO, is packed as an oxygen reference electrode, into the composite solid electrolyte Tamman tube B and after an Mo lead wire C is inserted therein, the open end of the Tamman tube B is sealed with inorg. cement D, etc., to form the sensor. The Mo lead wire on a molten metal side and this sensor are immersed into the molten metal, by which the electromo tive force corresponding to the concn. of the component to be measured is generated between the two Mo leads. The concn. of this component is known by calculation or by a calibration curve.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an oxygen concentration battery type sensor for molten metal components using a composite solid electrolyte.

[Conventional technology]

In the ferrous and non-ferrous thin metal industry, it is important to measure the concentration of various constituent elements in the molten state during various processes such as smelting, refining, and casting of these metals, from the viewpoint of process and product quality control, and also in the future. This is an important issue for the improvement of Conventionally, these measurements were carried out by chemical analysis or instrumental analysis of sampled samples, but recently there has been a demand for various sensors that can obtain measurement results on the spot due to cost and time considerations, and some sensors are now in practical use. For example, there are oxygen sensors for measuring the oxygen concentration in molten steel, and silicon sensors that are applied to oxygen sensors for measuring the silicon concentration in molten pig iron.

[Problem to be solved by the invention]

One of the component concentration sensors for molten metal currently proposed is one that applies the principle of an oxygen sensor found in silicon sensors. In other words, if the component element to be measured in the molten metal is in equilibrium with dissolved oxygen, and the temperature is constant or known, the concentration of the component element can be indirectly determined from the equilibrium constant by measuring the oxygen concentration. It can be done. Generally, the component element to be measured is not in an equilibrium state with oxygen, so for example, it is necessary to force an equilibrium by placing an oxide of the component element near the oxygen sensor. If the change in the concentration of 0 due to equilibrium movement is not small, the error will be large and it is not practical, so it is necessary to select an oxide containing that component that suits the measurement situation.
For example, in a silicon sensor for molten pig iron, silicon dioxide is adhered to the outside of the magnesium oxide partially stabilized zirconia solid electrolyte tube of a normal oxygen sensor for molten steel with an organic binder, or magnesium silicate is dispersed in the solid electrolyte itself. ing. However, the former requires an extra adhesion process and has the problem that the silicon dioxide peels off during use because it is an organic binder, while the latter has the advantage of being able to be manufactured at once using raw materials pre-mixed with silicate, but cannot be used at high temperatures. There is a problem with thermal shock resistance. Although devices that apply the principle of oxygen sensors have been proposed in this way, improvements in performance have been required, and they are not suitable for general-purpose practical use. Therefore, the present invention provides a sensor that can measure the concentration of component elements in molten metal at low cost, quickly, and with high precision.

[Means to solve the problem]

Therefore, the present invention uses partially stabilized magnesium oxide zirconia as a solid electrolyte base, and uses a composite solid electrolyte in which a mixture of an oxygen ion conductor and an oxide containing an element to be measured is integrated on the base. This is an oxygen a battery type component concentration sensor for molten metal. In addition, the thickness of the composite solid electrolyte is 0.11-3 cm or less, and the thickness of the mixture is 5 pm or more and the total
It is optimal if they are integrated in a layered manner with a thickness of 0% or less. Further, it is preferable that the proportion of the oxygen ion conductor in the mixture is 40% or more and 99% or less. Furthermore, the oxygen ion conductor in the mixture is zirconia partially stabilized by an alkaline earth metal oxide,
Moreover, it is more effective if the oxide containing the component element to be measured is a composite oxide of the oxide of the component element and an alkaline earth metal oxide. (b) Magnesium oxide partially stabilized zirconia was used as the solid electrolyte because it is widely used as a solid electrolyte in oxygen sensors for molten steel, and it has excellent impact resistance, quickness, and high accuracy over a wide concentration range. This is because it has the ability to measure the oxygen concentration of molten steel and other non-ferrous metals. (0) Magnesium oxide partially stabilized zirconia. Zirconia containing 3 to 13 mol% of magnesium oxide is molded into a predetermined shape such as a Tammann tube, a rod or a disc,
It is sintered at 1,400 to 1,800°C, and the manufacturing method for solid electrolytes for ordinary oxygen sensors for molten steel can be applied. (c) The oxygen ion conductor in the mixture is mainly zirconia partially stabilized with alkaline earth metal oxides such as magnesium oxide and calcium oxide, and also zirconia and yttrium oxide. Combinations of cerium oxide, various other types of zirconia, and their stabilizers can be used. The stabilizer is 2
In addition to the zirconia type, hafnia type, thoria type, and other oxygen ion conductors can also be used. The reason why the proportion of the oxygen ion conductor in the mixture is set to 40% or more and 99% or less is that the sensor of the present invention can maintain the oxygen ion conductive performance and retain the necessary amount of oxide containing the component element to be measured. This is to demonstrate performance. (d)′JJ? Examples of oxides containing Jll constant target component elements in the compound include silicon dioxide, magnesium E1 acid, aluminum silicate, etc., when the first component element is silicon. That is, it is an oxide of its component element or a composite oxide with other oxides, and other oxides are preferably alkaline earth metal oxides such as magnesium oxide and calcium oxide, but are not limited to these. Therefore, when the target component element is aluminum, it is aluminum oxide, magnesium aluminate, etc., when it is phosphorus, it is phosphorus oxide, calcium sulfate, sodium phosphate, etc., and when it is chromium, it is chromium oxide, Examples include magnesium chromate. (Book) Magnesium oxide partially stabilized zirconia substrate,
Integrating the mixture with the oxide containing the component element to be measured in the PM elementary bioionic conductor can be carried out, for example, by baking the mixture after sintering the substrate, or by attaching the mixture to the green green compact of the substrate. This can be done by sintering it later. The mixture may be applied as a layer on the substrate or may be applied intermittently to be integrated. Further, the thickness of the mixture must be 5 pLm or more, since performance cannot be fully exhibited if it is too thin, and 30% or less of the total composite solid electrolyte is appropriate, since impact resistance deteriorates if it is too thick. (f) The thickness of the composite solid electrolyte is preferably 0.1 mm or more in order to maintain its electrolytic performance, and 3 mm or less in order not to impair thermal shock resistance or response performance. (g) The assembly of a component concentration measurement sensor for molten metal using these composite solid electrolytes may be the same as a normal oxygen sensor, that is, as an oxygen reference electrode, No + MeO
2, Or + Cr2O3, Fe + Fed. Mixed powder A of (metals and metal oxides) such as Xi + NiO
is packed in a composite solid electrolyte Tammann tube B with 1Mo lead &
! After inserting the aC, the open end of the Tammann tube may be sealed with inorganic cement D or the like to form a sensor (see Figure 1). By immersing the molten metal lead wire and this sensor, an electromotive force corresponding to the concentration of the component to be measured is generated between the two leads, and the concentration of that component can be determined by calculation or a calibration curve. You will be able to do that. Hereinafter, five aspects of the present invention will be explained in detail.

[Example 1] A mixture of 20% magnesium silicate and 80% of zirconia partially stabilized with 7 mol% magnesium oxide was added to the outer surface of a Tamman tube-shaped zirconia containing 7 mol% magnesium oxide. A slurry of powder was applied. After drying, it was sintered at 1.700° C. to obtain a Tammann tube sintered body having an inner diameter of 3.5 mm, an outer diameter of 5 mm, a diameter of 7 ta, and a length of 35+ sm. In addition, since the outer diameter of the part to which the mixed powder slurry was not applied was 5.51 mm, the thickness of the layer of the mixture was 0.5 mm.
It was found to be 1mm. And (M(+ + M2O3
) R gold powder was filled as an oxygen reference electrode, and a silicon sensor element was prepared by a conventional method. 7Erosilicon was added to pig iron at 1500° C. that had been high-frequency melted in a magnesium oxide crucible to give a silicon concentration of 0.2%, a silicon sensor was immersed together with a No. 2 bar serving as a counter electrode, and the electromotive force was measured with a recorder. Similar tests were conducted on molten pig iron containing 0.5% and 1.0% silicon, respectively. FIG. 2 shows the relationship between electromotive force and silicon concentration, and it can be seen that there is good correspondence. The response time was good at 8 to 11 seconds, and no cracks occurred in the sensor after immersion.

Example 2 The outer surface of a sintered Tammann tube of 8 mol% magnesium oxide partially stabilized zirconium was coated with 50% quartz and 50% 1
A mixed powder of 0 mol % calcium oxide partially stabilized zirconium was applied, and after drying, it was baked at 1,400°C. The thickness of the baked layer was 4i0.021mm. Similar to Example 1, a silicon sensor was assembled and an immersion experiment in silicon-containing molten pig iron was conducted, and the results shown in FIG. 3 were obtained. According to this, the electromotive force and silicon concentration showed a good correlation, the response time was 7 to 9 seconds, and no cracking occurred during immersion.

[Example 3] A mixed powder of 10% magnesium chromate and zirconia containing magnesium oxide equivalent to 7 mol% of 90% was placed on the outer surface of a Tammann tube molded body of partially stabilized zirconia containing 9 mol% of magnesium oxide. The slurry was applied and, after drying, sintered at 1,850°C. The thickness of the mixture layer of the obtained sintered Tammann tube was 0.05 am e (N
A chromium sensor filled with o + M (+02) mixed powder was prepared, and ferrochrome was used in the same manner as in Example 1.
According to FIG. 4, which shows the results of immersion in molten steel, there is a good correlation between the electromotive force and the chromium concentration. Response speed is 8-10
seconds, and no cracks occurred in the sensor.

[Example 4] 8% calcium phosphate and 92% calcium phosphate were added to the outer surface of a Tamman tube molded body of zirconia containing 7 mol% magnesium oxide.
A mixed powder slurry of 10 mol % oxidizing power of partially stabilized zirconia with lucium was applied, and after drying, it was sintered at 1,700°C. The thickness of the obtained mixed powder layer was 0.13 mm.* A phosphorus sensor filled with (No + No. 02) mixed powder was prepared, and the thickness of each layer was 0.01 mm using phosphorous iron in the same manner as in Example 1. .0.05, O. It was immersed in 1450°C molten pig iron containing 1% phosphorus. According to the results in FIG. 5, there is a good correlation between the electromotive force and the phosphorus concentration. The response speed was 7 to 12 seconds, and no cracks occurred in the sensor.

【Effect of the invention】

As described above, according to the present invention, the concentration of component elements in molten metal can be measured at low cost, quickly, and with high precision. Further, according to the second aspect of the present invention, stable measurements can be performed without causing cracks. The third aspect of the present invention has the effect of stabilizing the performance. Furthermore, according to the fourth aspect of the present invention, the performance is even more stable.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a Tammann tube type sensor according to an embodiment of the present invention, and FIG. 2 is a diagram of experimental data of the first embodiment. 3 is an experimental data diagram of Example 2, FIG. 4 is an experimental data diagram of Example 3, and FIG. 5 is an experimental data diagram of Example 4.

Claims (4)

[Claims] (1) A composite solid electrolyte is used, in which partially stabilized magnesium oxide zirconia is used as a solid electrolyte base, and a mixture of an oxygen ion conductor and an oxide containing an element to be measured is integrated on the base. Oxygen concentration battery type component concentration sensor for molten metal. (2) The thickness of the composite solid electrolyte is 0.1 mm or more and 3 mm or less, and the thickness of the mixture is 5 μm or more and 30% of the total
The component concentration sensor for molten metal according to claim 1, which is integrated in a layered manner with a thickness of: (3) The component concentration sensor for molten metal according to claim 1 or 2, wherein the proportion of the oxygen ion conductor in the mixture is 40% or more and 99% or less. (4) The oxygen ion conductor in the mixture is zirconia partially stabilized by an alkaline earth metal oxide, and the oxide containing the component element to be measured is a mixture of the oxide of the component element and the alkaline earth metal oxide. The component concentration sensor for molten metal according to claim 1, 2 or 3, which is a composite oxide of .