JPH039068B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is mainly applicable to the measurement of temperature in hot metal and molten steel in blast furnaces, open hearths, and converters, as well as measurement of dissolved oxygen content, carbon content, etc., and consumable immersion for the purpose of sampling. Regarding the heat-resistant protection tube of the probe. [Prior art] In recent years, in order to rationalize and improve quality control in the iron and steel manufacturing fields, for example, converter furnaces, electric furnaces,
In the casting process, temperature is measured using a consumable thermocouple, which is a rapid immersion thermocouple method, for the purpose of temperature control, and in the converter and casting processes, carbon Consumable multi-purpose measuring elements (sublance, etc.) are used for measuring oxygen content and sampling, etc., and play an extremely important role in quality control and operation. These consumable thermocouples and consumable multi-purpose measuring elements are so-called consumable immersion probes, which have a heat-resistant protection tube attached to the part that is immersed in molten steel or hot metal during measurement to prevent thermal deterioration and improve corrosion resistance. Asbestos sleeves, ceramic fiber sleeves, etc. are used as the heat-resistant protective tube. [Problems to be Solved by the Invention] However, these expendable immersion probes equipped with heat-resistant protection tubes cause many problems when immersed in molten steel or hot metal, and have never reached a satisfactory state. In other words, when a sleeve containing asbestos as the main component is used as a heat-resistant protective tube, it is inexpensive, but
As the heat resistance and corrosion resistance are extremely low, the asbestos sleeve will disappear during immersion, and probes equipped with asbestos sleeves will be burnt out in molten steel or hot metal during immersion, causing splash, or when being lifted from molten steel or hot metal. Only the immersed portion may remain in the molten steel or hot metal as an impurity. Also, contamination of the working environment due to the use of asbestos,
In other words, it can cause asbestos pollution,
Its use is becoming severely restricted. On the other hand, sleeves whose main component is ceramic fiber can be roughly divided into (a) those obtained by vacuum suction molding from an aqueous slurry containing defibrated ceramic fibers and a binder and drying; There are two types of sleeves: (b) sleeves that are hardened with an inorganic binder, and sleeves that are made by winding a paper-like material whose main component is ceramic fiber in multiple layers; Although it is an inorganic fiber with higher heat resistance than asbestos, it does not have the necessary density required for erosion resistance, and a binder, which is applied to further increase the density, is used. Due to significant unevenness in the degree of hardening by the coating material, durability performance varies, and deformation that occurs during removal from the mold after vacuum suction molding makes it difficult to obtain a sleeve with desired precision. On the other hand, in the latter case (b), hardening can be done at the stage of winding in multiple layers, so there is no significant unevenness in the hardening, but the hardening is particularly difficult to achieve in order to have sufficient erosion resistance against the slag that comes into contact with it during dipping. In addition to lacking in properties, the ceramic fiber is first formed into a paper shape and then formed into a cylindrical shape, making it very expensive and unsuitable for use as a consumable item.Like the former, it is by no means satisfactory. As described above, consumable immersion probes equipped with conventional heat-resistant protection tubes cannot be used stably due to insufficient corrosion resistance against hot metal, molten steel, and slag, and probes equipped with asbestos sleeves cannot be used stably. ,, Asbestos dust causes a deterioration of the working environment, and in addition, various improvements have been made to consumable immersion probes equipped with ceramic fiber multilayer sleeves, which are unsuitable for use as consumables because the sleeves are too expensive. There are some issues that should be addressed. [Means and effects for solving the problems] By solving the above-mentioned drawbacks, the present invention has excellent heat insulation properties and corrosion resistance when immersed in hot metal or molten steel, can be used stably, and is extremely inexpensive. The object of the present invention is to provide a consumable immersion probe equipped with a heat-resistant protection tube. That is, the present invention measures the temperature in hot metal and molten steel,
Furthermore, it relates to a heat-resistant protection tube that is attached to the outside of the immersion part of a consumable-type immersion probe such as a consumable thermocouple or a sublance that measures dissolved oxygen content, carbon content, etc., and the heat-resistant protection tube is made of ceramic fiber 60.
~95% by weight, 5-40% by weight of clay, and organic molding aids.
A composition consisting of 10% by weight or less and having a bulk density of
The above objective can be achieved by providing a heat-resistant protective tube characterized by having a heat resistance of 0.5 to 1.2 g/cm ³ . Ceramic fiber is used as the inorganic fiber material used in the present invention in order to have excellent heat resistance, heat insulation, and spalling resistance, and if particularly high heat resistance is required, alumina fiber is used as the inorganic fiber material. Crystalline fibers, mullite crystalline fibers, etc. can also be used. Ceramic fiber is particularly preferred because it has sufficient durability and is inexpensive for short-term immersion in hot metal, molten steel, and slag. The reason why the content of ceramic fiber, which is the main material, is limited to a range of 60 to 95% by weight is that if it is less than 60% by weight, it will not be possible to obtain a product with excellent heat insulation and spalling resistance. This is because if it exceeds the weight percentage, the handling strength and hot strength will become too small. Further, the clay used in the present invention may be any clay that has binding strength, plasticity, and fire resistance, such as montmorillonite, hectorite, bentonite, acid clay, kaolin, and Kibushi clay. Particularly preferred are montmorillonite and hectorite, which have the plasticity to impart shape retention to the molded product during molding, and the bonding strength necessary to obtain handling strength and hot strength in small amounts. The reason why the amount of clay added is limited to the range of 5 to 40% by weight is that if it is less than 5% by weight, sufficient handling strength and hot strength will be low;
This is because if the content exceeds % by weight, the handling strength and hot strength will be sufficiently high, but the heat spalling resistance and heat insulation properties will decrease. Further, as the organic molding aid used in the present invention, any aid can be used as long as it can increase handling strength. However, it is preferable to use one or more selected from methylcellulose, hydroxymethylcellulose, phenol, and acrylic ester, which are effective in small amounts. The reason why the amount of forming aid added is limited to 10% by weight or less is that if it exceeds 10% by weight, it will generate smoke or splash when immersed in molten steel or hot metal, causing a deterioration of the working environment. This is because probes for measuring quantities and the like tend to cause measurement errors. In addition to the above-mentioned constituent materials of the heat-resistant protection tube of the present invention, refractory powders such as alumina, mullite, and siyamoto, magnesia, chromium oxide, magnesia-chromia spinel, and silicon carbide may be used for the purpose of corrosion resistance or cost reduction. Refractory powder with high corrosion resistance can be added. Furthermore, for the purpose of further increasing handling strength and hot strength, general heat-resistant inorganic binders such as colloidal silica, colloidal alumina, basic aluminum chloride, aluminum phosphate, and ammonium phosphate can be added. In the heat-resistant protective tube of the present invention, the ceramic fibers are partially defibrated and are uniformly dispersed in a composition mainly composed of the clay and the organic forming aid, The remainder is particle size 5
It is preferable that the particles have a structure covered with a composition in which the ceramic fibers are uniformly dispersed around the particles. By having such a structure, the heat-resistant protection tube can significantly increase its strength while maintaining the high heat insulation properties and heat spalling resistance inherent to the fibrous molded body. The particle size of the ceramic fiber particles is 5.
The reason why the particle size is less than 5 mm is that if the particle size of the granules exceeds 5 mm, sufficient handling strength and hot strength cannot be obtained, especially in the case of a thin-walled heat-resistant protective tube. The bulk density of the heat-resistant protection tube of the present invention is 0.5 to 1.2 g/cm ³
The reason for limiting the range is that if the bulk density is less than 0.5 g/ ^cm3 , the porosity will increase even if the constituent materials have excellent corrosion resistance. It is prone to invasion and is subject to rapid erosion. On the other hand, if the bulk density exceeds 1.2 g/ ^cm3 , the corrosion resistance against molten steel, hot metal and slag will improve, but it will be necessary to protect the paper sleeve that houses various measurements or functions inside the consumable probe. This is because the heat insulating properties are reduced and the heat spalling resistance is also reduced, making it impossible to perform the role as a heat resistant protective tube. The reason why the wall thickness of the heat-resistant protection tube of the present invention is limited to a range of 2 to 10 mm is that if the wall thickness is less than 2 mm, the inside of the probe will be exposed even when used for a short time (several seconds) only for temperature measurement. This is undesirable because it does not provide the necessary insulation and corrosion resistance for protection. On the other hand, if the wall thickness exceeds 10 mm, the insulation and corrosion resistance necessary to protect the inside of the probe will be significantly improved, but the quality will be excessive and the price will be too high, making it unsuitable for use as a consumable item. It is from. [Effects of the Invention] The thus obtained heat-resistant protective tube of the present invention has significantly superior heat resistance and corrosion resistance compared to the above-mentioned asbestos sleeve, and is also suitable for ceramic fiber wet vacuum suction molding sleeves and ceramic fiber paper multilayer wrapping. Compared to sleeves, the consumable type equipped with the heat-resistant protection tube has the necessary density to provide the corrosion resistance required for slag, hot metal, and molten steel, and also has superior high-temperature insulation properties. Immersion probes work ideally as sensors. In addition, the heat-resistant protective tube of the present invention is prepared by adding 60 to 130 parts by weight of water to 100 parts by weight of the above-mentioned constituent materials and kneading the mixture to obtain a plastic mixture. It is preferable to continuously form the pipe into a vacuum pipe using an extrusion molding machine in the department and dry it. Heat-resistant protective tubes produced by extrusion molding have no variations in composition or density, and molded products with good dimensional accuracy can be obtained. Therefore, unlike ceramic fiber wet vacuum suction molded sleeves, there are no variations in bulk density due to uneven hardening treatment, and even molding There are no quality problems such as poor dimensional accuracy due to deformation that occurs during subsequent demolding. Furthermore, since the heat-resistant protective tube of the present invention is continuously molded, the molding cost is 1/2 to 1/2 of that of ceramic fiber wet vacuum suction molding.
3. The expendable immersion probe equipped with the heat-resistant protection tube can be a sensor suitable for use as a consumable item, since it requires only 1/5 to 1/6 of the ceramic fiber paper multilayer wound sleeve. Next, an example of a consumable immersion probe equipped with the heat-resistant protection tube of the present invention will be described in comparison with a comparative example. Example 1 Ceramic fiber was cut using a cutter mill for 10
A chip-like bulk with a size of mm or less, the ceramic fiber, montmorillonite and hectorite as clay, methyl cellulose and phenol as organic forming aids, colloidal silica as an inorganic binder, mullite powder as an inorganic filler, and water. were mixed in the combinations shown in Table 1 and kneaded in a kneader. Subsequently, a cylindrical sleeve was formed using an extrusion molding machine having an extrusion port in which a circular medium ball with an outer diameter of 40 mm was arranged concentrically inside a circular nozzle with an inner diameter of 50 mm, and the sleeve was cut into a length of 300 mm and dried. The quality obtained is also shown in Table 1. The inorganic fiber sleeve obtained in this way was attached to the outside of a consumable thermocouple as shown in Figure 1, and the probe was placed on a steel containing basic slag whose molten metal temperature was previously maintained at 1700°C in an induction heating furnace. After immersing it in the water for 20 seconds, we checked its durability. The results are also shown in Table 1. Comparative Example 1 A cylindrical molded body was molded by vacuum suction molding from a slurry containing ceramic fibers in water, colloidal silica as a binder, and polyacrylamide as a molding aid, and dried to an outer diameter of 50 mm.
The molded article had a thickness of 5 mm, a length of 300 mm, and a bulk density of 0.3 g/cm ³ . Thereafter, it was hardened with colloidal silica to obtain a ceramic fiber sleeve with a bulk density of 0.5 g/cm ³ . The thus obtained sleeve was attached to a consumable thermocouple in the same manner as in Example 1, and a durability test was conducted. The results are shown in Table 2. Comparative Example 2 A slurry of ceramic fibers in water, latex as a binder, and aluminum sulfate as a forming aid was made into a paper using a round mesh paper machine, dried, and cut into paper sheets with a wall thickness of 0.5 mm and a bulk density of 0.25 g. /
A ceramic fiber paper of cm ³ was obtained. After that, the ceramic fiber paper with an inner diameter of 40
The product was wound in multiple layers to form a molded product with a thickness of 5 mm, a wall thickness of 5 mm, and a length of 300 mm, and then hardened with colloidal silica to obtain a ceramic fiber sleeve with a bulk density of 0.55 g/cm ³ . The thus obtained sleeve was attached to a consumable thermocouple in the same manner as in Example 1, and a durability test was conducted. The results are shown in Table 2.

【table】

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a perspective view of one type of expendable immersion probe. FIG. 2 is a sectional view showing an example of a consumable thermocouple. 1...Protective cap made of steel plate, 2...Ceramics, 3...
...Heat-resistant protection tube, 4...Paper tube, 5...Paper tube, 6...
Steel pipe, 7...PR thermocouple, 8... Compensation lead wire.

Claims (1)

[Claims] 1. Ceramic fiber 60-95% by weight and clay 5.
~40% by weight and 10% by weight or less of an organic forming aid, and a composition consisting mainly of ceramic fibers in a defibrated state, ceramic fiber granules with a particle size of 5 mm or less, clay, and an organic forming aid. The bulk density is 0.5 to 1.2g/
cm ³ heat-resistant protection tube. 2. The heat-resistant protection tube according to claim 1, wherein the protection tube has a wall thickness of 2 to 10 mm. 3. The heat-resistant protection tube according to claim 1 or 2, wherein the protection tube is formed by an extrusion molding machine.