JPH0786499B2 - Component concentration sensor for molten metal using composite solid electrolyte - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

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

[Prior art]

In the ferrous and non-ferrous metal industries, measuring the concentrations of various constituent elements in the molten state in various processes such as smelting, refining, and casting of those metals is important from the viewpoint of process and product quality control. It is also an important issue for the improvement of. Conventionally, these measurements have been performed by chemical analysis or instrumental analysis of sampling samples, but recently, various sensors that can obtain measurement results on the spot have been demanded from the viewpoint of cost and time, and some have been put to practical use. For example, there is an oxygen sensor for measuring the oxygen concentration in molten steel, and there is a silicon sensor to which the oxygen sensor is applied for measuring the silicon concentration in molten pig iron.

[Problems to be Solved by the Invention]

One of the currently proposed concentration sensors for molten metal is an application of the principle of the oxygen sensor found in silicon sensors. That is, when the component element to be measured in the molten metal is in equilibrium with dissolved oxygen, the concentration of that component element can be indirectly determined from the equilibrium constant by measuring the oxygen concentration if the temperature is constant or known. You can do it. In general, the component element to be measured is not in equilibrium with oxygen, so for example, an oxide of that component element should be present near the oxygen sensor to forcibly create equilibrium. At this time, if the concentration of the component element does not change greatly due to the equilibrium movement, the error becomes large and it is not practical. Therefore, it is necessary to select an oxide containing the component suitable for the measurement situation. For example, in a silicon sensor for molten pig iron, silicon dioxide is bonded to the outside of the solid electrolyte tube of magnesium oxide partially stabilized zirconia of an oxygen sensor for normal molten steel with an organic binder, or magnesium silicate is dispersed in the solid electrolyte itself. ing. However, in the former case, there is a problem that an extra bonding step is required and the silicon dioxide peels off during use due to the organic binder, and in the latter case, there is an advantage that it can be manufactured at once using a raw material in which silicate is mixed, but at a high temperature. There is a problem in thermal shock resistance. As described above, the one applying the principle of the oxygen sensor has been proposed, but it is not suitable for general-purpose practical use because improvement of performance is required. Therefore, the present invention provides a sensor which can inexpensively, quickly, and highly accurately measure the concentration of a constituent element in molten metal.

[Means for Solving the Problems]

Therefore, the present invention uses a magnesium oxide partially stabilized zirconia as a base material of a solid electrolyte, and uses a composite solid electrolyte formed by integrating a mixture of an oxygen ion conductor and an oxide containing a component element to be measured on the basis. Is a concentration sensor for molten metal component concentration of oxygen concentration battery. It is optimal that the composite solid electrolyte has a thickness of 0.1 mm or more and 3 mm or less, and the mixture has a thickness of 5 μm or more and is 30% or less of the total thickness in a layered form. Also, the proportion of oxygen ion conductor in the mixture should be 40% or more 99
% Or less is good. Further, the oxygen ion conductor in the mixture is zirconia partially stabilized by an alkaline earth metal oxide,
It is even more effective if the oxide containing the component element to be measured is a composite oxide of the oxide of the component element and the alkaline earth metal oxide. (B) Here, magnesium oxide partially stabilized zirconia was used as a solid electrolyte because it is used in large quantities as a solid electrolyte for oxygen sensors for molten steel, and has excellent impact resistance and a wide concentration range with rapid and high accuracy. This is because it has the ability to measure the oxygen concentration of, and is widely used for molten copper and other non-ferrous metals. (B) Magnesium oxide partially stabilized zirconia is 3 to
Zirconia containing 13 mol% magnesium oxide is molded into a predetermined shape such as a Tammann tube, rod shape, disk shape, etc.
It is sintered at 1800 ° C, and it is possible to apply the usual solid electrolyte manufacturing method for oxygen sensors for molten steel. (C) The oxygen ion conductor in the mixture is mainly zirconia partially stabilized by an alkaline earth metal oxide such as magnesium oxide or calcium oxide. In addition, zirconia and yttrium oxide, cerium oxide, and various other zirconia A combination with the stabilizer can be used. You may use together 2 or more types of the stabilizer. In addition to zirconia, hafnia, thoria,
Other oxygen ion conductors can also be used. The proportion of oxygen ion conductor in the mixture is 40% or more 99
The reason for setting the content to be not more than% is to maintain the oxygen ion conductive performance and to hold the required amount of the oxide containing the component element to be measured to exhibit the sensor performance of the present invention. (D) The oxide containing the component element to be measured in the mixture is, for example, silicon dioxide, magnesium silicate or aluminum silicate when the target component element is silicon. That is, it is an oxide of the component element or a composite oxide with another oxide, and the other oxide is preferably an alkaline earth metal oxide such as magnesium oxide or calcium oxide, but is not limited thereto. . Therefore, when the target component element is aluminum, it is aluminum oxide, magnesium aluminate, etc., when it is phosphorus, it is phosphorus oxide, calcium phosphate, sodium phosphate, etc., and when it is chromium, it is chromium oxide, magnesium chromate, etc. . (E) Magnesium oxide partially stabilized zirconia substrate,
Integrating the mixture of the oxygen ion conductor and the oxide containing the component element to be measured includes, for example, baking the mixture after sintering of the base, and adhering the mixture to the green body compact of the base. It can be carried out by sintering later. The mixture may be layered on the substrate or may be intermittently applied and integrated. Further, if the thickness of the mixture is too thin, the performance cannot be sufficiently exhibited, so that the thickness is required to be 5 μm or more, and if it is too thick, the impact resistance is deteriorated, so 30% or less of the whole composite solid electrolyte is appropriate. (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 so as not to impair thermal shock resistance and response performance. (G) The assembly of the component concentration rate sensor for molten metal using these composite solid electrolytes may be the same as that for a normal oxygen sensor. That is, as the oxygen reference electrode, _Mo + _Mo O ₂ , Cr + Cr ₂
O _3, Fe + FeO, (metal + metal oxide) such as Ni + NiO mixed powder A packed into a composite solid electrolyte Tammann tube B, M _o lead C
After inserting, the open end of the Tammann tube may be sealed with an inorganic cement D or the like to form a sensor (see FIG. 1). By immersing the molten metal side in the _Mo lead wire and this sensor, an electromotive force corresponding to the concentration of the component to be measured is generated between both _Mo leads, and the concentration of that component can be known by calculation or calibration curve. You will be able to Examples of the present invention will be described below.

Example 1 Mixing 20% magnesium silicate and 80% zirconia partially stabilized with 7 mol% magnesium oxide on the outer surface of a zirconia tanman tube shaped body containing 7 mol% magnesium oxide. A slurry of powder was applied. After drying, it is sintered at 1,700 ℃ and has an inner diameter of 3.5 mm, an outer diameter of 5.7 mm and a length of 35 m.
A m-shaped Tammann tube sintered body was obtained. Since the outer diameter of the portion not coated with the mixed powder slurry was 5.5 mm, the thickness of the mixture layer was determined to be 0.1 mm. And (M _o + M _o O
₂ ) The mixed powder was filled as an oxygen reference electrode, and a silicon sensor element was prepared by a conventional method. Ferrosilicon was added to 1500 ° C. for pig iron and high-frequency melted in magnesium oxide crucibles, and 0.2% silicon concentration, a silicon sensor immersed with M _o rod as the counter electrode, were measured electromotive force recorder. Similarly, molten pig iron containing 0.5 and 1.0% silicon was also tested. FIG. 2 shows the relationship between the electromotive force and the silicon concentration, and it can be seen that a good correspondence is shown. The response time was as good as 8 to 11 seconds, and the sensor after immersion did not crack.

Example 2 Sintering of 8 mol% magnesium oxide partially stabilized zirconium The outer surface of a Tammann tube was coated with a mixed powder of 50% quartz and 50% 10 mol% calcium oxide partially stabilized zirconium. After drying, it was baked at 1,400 ° C.
The thickness of the baking layer was 0.02 mm. A silicon sensor was assembled in the same manner as in Example 1, 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 the 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 90% zirconia containing 7% by mole of magnesium oxide was formed on the outer surface of a Tammann tube molded body of 9% by mole of magnesium oxide partially stabilized zirconia. After applying the slurry and drying, 1,
Sintered at 650 ° C. The thickness of the mixture layer of the obtained sintered Tammann tube was 0.05 mm. Chromium sensors filled with (M _o + M _o O ₂ ) mixed powder were prepared and ferrochrome was used in the same manner as in Example 1 to contain 1,5,10,20% chromium, respectively.
It was immersed in molten steel at 600 ° C. According to the result of FIG. 4, the electromotive force and the chromium concentration show a good correlation. The response speed was 8 to 10 seconds, and the sensor did not crack.

Example 4 8% calcium phosphate and 92% calcium phosphate were formed on the outer surface of a Tamman tube molding of zirconia containing 7 mol% magnesium oxide.
A mixed powder slurry with 10 mol% calcium oxide partially stabilized zirconia was applied, dried and then sintered at 1,700 ° C. The thickness of the obtained mixed powder layer was 0.13 mm. (M _o +
M _o O ₂₎ mixed powder to prepare a phosphorus sensor stuffed were immersed in 1450 ° C. molten pig iron contain respectively 0.01,0.05,0.1% phosphorus with phosphorus iron in the same manner as in Example 1. According to the result of FIG. 5, the electromotive force and the phosphorus concentration show a good correlation. The response speed was 7 to 12 seconds, and the sensor did not crack.

【The invention's effect】

As described above, according to the present invention, there is an effect that the concentration of the constituent element in the molten metal can be measured inexpensively, quickly and highly accurately. In addition, according to the second aspect of the present invention, stable measurement can be performed without causing cracks. The third aspect has the effect of stabilizing the performance. Further, in the fourth aspect, the performance is further stabilized.

[Brief description of drawings]

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

Claims (4)

[Claims] 1. A composite solid electrolyte comprising magnesium oxide partially stabilized zirconia as a solid electrolyte substrate and a mixture of an oxygen ion conductor and an oxide containing a component element to be measured integrated on the substrate. Characteristic oxygen concentration cell type concentration sensor for molten metal. 2. The molten metal according to claim 1, wherein the thickness of the composite solid electrolyte is 0.1 mm or more and 3 mm or less, and the mixture is layered to a thickness of 5 μm or more and 30% or less of the whole. Component concentration sensor. 3. The proportion of oxygen ion conductor in the mixture is 40%.
The concentration sensor for molten metal according to claim 1 or 2, wherein the concentration is not less than 99%. 4. The oxygen ion conductor in the mixture is zirconia partially stabilized by an alkaline earth metal oxide, and the oxide containing the constituent element to be measured is an oxide of the constituent element and an alkaline earth metal. The component concentration sensor for molten metal according to claim 1, 2 or 3, which is a complex oxide with an oxide.