JPH08271347A - Molten metal temperature sensor - Google Patents

Abstract

PURPOSE: To provide a molten metal temperature sensor which is acidic-resistant to oxygen in smelting, oxygen in the atmosphere, and oxygen in a slug and corrosion-resistant to molten metal, and can stably take a continuous temperature measurement over a long time. CONSTITUTION: This temperature sensor is essentially formed of an alumina insulating tube 2 having a thermocouple 1 sealed therein; an alumina protecting tube 3 containing the alumina insulating tube 2; and a high melting point composite protecting tube 4 having coatings (an inside coating 6a and an outside coating 6b) on the inner and outer surfaces. The inside coating 6a and the outside coating 6b are formed of a coating material containing one kind of ZrO2 aggregates and Zr O2 aggregates containing Y2 O3 , CaO or MgO, and a partial hydrolysate mainly consisting of Si alkoxide as binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal temperature sensor for continuously measuring the temperature of molten metal or the like,
In particular, it relates to a molten metal temperature sensor having a temperature measurement protection tube for protecting the sensor.

[0002]

2. Description of the Related Art Conventionally, molten metal of molten metal such as hot metal and molten steel
In order to measure the temperature of the (melt), "a consumable thermometer in which the tip of a platinum-rhodium thermocouple is protected by a quartz tube" is generally used.

In the above conventional consumable thermometer, when the thermocouple is immersed in molten pig iron, molten steel, etc., the heat-sensitive part is melted in an extremely short time (10 to 20 seconds), which makes it unusable. ing. Therefore, when using this consumable thermometer,
There was a problem that the temperature measurement had to be completed in a short time, and the thermocouple had to be replaced after each measurement. Therefore, it is difficult to control the quality and operation of molten metal such as hot metal and molten steel, and the temperature measurement cost is high. Therefore, the advent of a thermometer capable of continuously measuring temperature for a long time is strongly desired.

In order to meet the above demands, recently, a temperature sensor for molten metal having a thermocouple protection tube of ZrB ₂ type, Mo-ZrO ₂ type, BN type or the like having a high corrosion resistance to molten metal has been provided. For example, (1) JP-A-1-321326 discloses: A composition "ZrB ₂ as a main component and SiC and BN as auxiliary components
A body of ZrB ₂ system consisting of rB ₂ : 95 to 70 wt%, SiC: 1 to 15 wt%, BN: 4 to 29 wt%, ・ A composition of "Zr with a thickness of 30 μm or more provided on the inner surface of the body.
_{B 2: 50~100wt%, SiO 2} : 0~50wt% " of oxide layer was provided on the outer surface of the-body, thickness composition in 500～2000Myuemu" refractory powder: 50 to 85 wt%, the glass product: A ZrB ₂ type protective tube composed of a glass layer composed of 50 to 15 wt%, an inorganic fiber layer provided on the outer surface of the glass layer is disclosed.

(2) In the catalog issued by TYK Co., Ltd., there is a Mo-ZrO ₂ type protective tube having a composition of "ZrB ₂ : 20-25 wt%, Mo: 75-80 wt%". On the bath surface
A protective tube for continuous temperature measurement of molten metal provided with Al ₂ O ₃ -C type, ZrO ₂ -C type and MgO-C type refractory sleeves is provided.
Further, (3) Jpn. Pat. Appln. KOKAI Publication No. 5-27256, the composition "BN: 50 wt.
%, AlN: less than 50 wt% ", a BN-based protective tube is disclosed.

[0006]

[Problems to be Solved by the Invention]
The ZrB ₂ type protection tube of (1) shows extremely strong characteristics (corrosion resistance) to molten metal, especially molten steel, but is oxidized to oxygen in molten steel, oxygen in atmosphere and oxygen in slag. It has the drawback of

Further, in the ZrB ₂ type protection tube of (1) above, the ZrB ₂
The oxide layer on the inner surface of the ₂ based protective tubes, glass layers respectively provided on the outer surface, further inorganic fiber layer provided on the outside of the glass layer, thereby ZrB ₂ based antioxidant and easy cracking of the protective tube ZrB ₂ The thermal shock resistance of is improved. But,
In the ZrB ₂ type protection tube having such a configuration, it is effective for molten steel, but for slag with strong chemical activity, the glass layer is low-melting and melts into the slag, and a porous inorganic The fiber layer cannot suppress the intrusion of slag, and as a result, Zr
B ₂ comes into direct contact with the slag and is oxidized and consumed, so that it cannot withstand long-term temperature measurement.

Even with the Mo-ZrO ₂ type protection tube of the above (2), although the corrosion resistance against molten steel is strong, the protection tube is essentially weak against oxidation, and oxidation occurs in slag containing a large amount of oxygen, resulting in thinning. It has the drawback of going forward. In addition, M in (2) above
The o-ZrO ₂ based protective tube, in order to prevent the oxidation loss of molten metal surface portion, namely a slag countermeasure, Al ₂ O ₃ -C based, ZrO ₂ -C
-Type, MgO-C type refractory sleeves are installed to increase the service life, but since it contains carbon, it has the problem that oxidation and erosion proceed. There is.

Compared with the ZrB ₂ type protection tube of (1) and the Mo-ZrO ₂ type protection tube of (2), the above-mentioned (3) BN type protection tube has much weaker oxidation resistance and oxygen content. It has a drawback that significant oxidation occurs in a large amount of slag.

As described above, the ZrB ₂ system of the above (1) and Mo-of the above (2)
In continuous temperature measurement with molten steel using ZrO ₂ type and BN type protection tubes of (3), both oxidation resistance and corrosion resistance during temperature measurement are weak,
It cannot withstand temperature measurement for a long time. Therefore, today, there is a strong demand for a protective tube for a thermocouple that can stably measure temperature for a long time.

An object of the present invention is to provide a temperature sensor for molten metal having a protective tube which meets the above-mentioned demand, and more specifically, it is acid resistant to oxygen in molten steel, oxygen in atmosphere and oxygen in slag. It is an object of the present invention to provide a temperature sensor for molten metal, which has a chemical conversion property, has corrosion resistance to molten metal, and can continuously and stably measure temperature for a long time.

[0012]

The present invention is based on the ZrB ₂ system, Mo-
In a temperature sensor for molten metal mainly composed of a high melting point composite protective tube such as ZrO ₂ type, BN type, etc .: ・ Specific ceramic coating on the inner and outer surfaces of the protective tube, that is, fire resistance of oxides, carbides and nitrides At least one kind of aggregate (specifically, ZrO ₂ aggregate, Y ₂ O ₃ , CaO or MgO)
At least one of ZrO ₂ aggregates containing strontium) and a coating material containing a partial hydrolyzate mainly composed of Si alkoxide as a binder "
Or, on the surface of the coating material layer coated on the outer surface of the protective tube, "using an aggregate and a frit-containing powder and a partial hydrolyzate mainly composed of Si alkoxide as a binder". A coating layer made of the above coating material is further provided via a coating layer made of "antioxidant",
Thereby, the temperature sensor for molten metal of the above-mentioned purpose is provided.

That is, the temperature sensor for molten metal according to the present invention
First, in a molten metal temperature sensor comprising an alumina protective tube containing a thermocouple and a high melting point composite protective tube fitted to the outside of the alumina protective tube, the inside and outside surfaces of the high melting point composite protective tube are , At least one of refractory aggregates of oxides, carbides, and nitrides (specifically, ZrO ₂ aggregate, Y ₂ O ₃ , CaO or MgO)
ZrO ₂ aggregate containing 1) and a coating material containing a partial hydrolyzate mainly composed of Si alkoxide as a binder (Claims 1 and 2). "First invention").

Further, a molten metal temperature sensor according to the present invention
Secondly, an alumina protective tube containing a thermocouple, a high melting point composite protective tube fitted to the outside of the alumina protective tube,
In a molten metal temperature sensor provided with a protective layer in the vicinity of slag immersion of the high melting point composite protective tube, the inner and outer surfaces of the high melting point composite protective tube and the outer surface of the protective layer are ZrO ₂ aggregate, Y ₂ O ₃ ，
One of ZrO ₂ aggregates containing CaO or MgO and a coating material containing a partial hydrolyzate mainly composed of Si alkoxide as a binder are coated (claim 3: hereinafter referred to as “Claim 3”). 2 invention ”).

Further, the temperature sensor for molten metal according to the present invention
Thirdly, in a molten metal temperature sensor comprising an alumina protective tube containing a thermocouple and a high melting point composite protective tube fitted to the outside of the alumina protective tube, the inside surface of the high melting point composite protective tube is , ZrO ₂ aggregate, at least one ZrO ₂ aggregate containing Y ₂ O ₃ , CaO or MgO and a coating material having a partial hydrolyzate mainly composed of Si alkoxide as a binder, and coated with After coating the outer surface of the high melting point composite protective tube with the above-mentioned coating material, further, an antioxidant having an aggregate and frit-containing powder and a partial hydrolyzate mainly composed of Si alkoxide as a binder, and the above-mentioned coating material. A plurality of layers are alternately coated (claim 4: hereinafter referred to as "third invention").

Further, the temperature sensor for molten metal according to the present invention
Fourthly, an alumina protective tube containing a thermocouple, a high melting point composite protective tube fitted to the outside of the alumina protective tube,
In the molten metal temperature sensor provided with a protective layer in the vicinity of the slag immersion of the high melting point composite protective tube, the inner surface of the high melting point composite protective tube is ZrO ₂ aggregate, Y ₂ O ₃ , CaO or MgO containing ZrO. ₂ a partial hydrolyzate mainly containing at least one and Si alkoxide aggregate binder - and computing, on the other hand, the outer surface of the refractory composite protective tube, co with the coating material - - co with a coating material to coating After that, further, a plurality of layers are coated alternately with an antioxidant and a coating material containing an aggregate and frit-containing powder and a partial hydrolyzate mainly composed of Si alkoxide as a binder, and the outer surface of the protective layer. Is coated with the antioxidant, and then coated with the coating material,
Alternatively, it is characterized by being further coated with the antioxidant (claim 5: hereinafter referred to as "the fourth invention").

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A molten metal temperature sensor according to the present invention (first to fourth inventions) will be specifically described below with reference to FIGS. 1 to 5. 1 to 4 show the first
The temperature sensor for molten metal, which is one embodiment of each of the invention to the fourth invention,
FIG. FIG. 5 is a sectional view showing another embodiment of the high melting point composite protective tube constituting the molten metal temperature sensor according to the present invention (first to fourth inventions).

As shown in FIG. 1, the molten metal temperature sensor according to the first aspect of the invention comprises an alumina insulating tube 2 enclosing a thermocouple 1, an alumina protective tube 3 containing the alumina insulating tube 2,
The main constituent is a high melting point composite protective tube 4 having coatings (inner coating 6a and outer coating 6b) on the inner and outer surfaces. In FIG. 1, 8 is a stainless steel protective tube and 9 is a terminal box.

As shown in FIG. 2, the molten metal temperature sensor according to the second aspect of the invention comprises an alumina insulating tube 2 enclosing a thermocouple 1, an alumina protective tube 3 containing the alumina insulating tube 2,
Refractory having a high melting point composite protective tube 4 having coatings on the inner and outer surfaces (inner coating 6a and outer coating 6b), and a coating 6c disposed in the vicinity of the slag immersion of the high melting point composite protective tube 4. The material sleeve 5 is the main component. In FIG. 2, 7 is cement, 8 is a stainless protective tube, and 9 is a terminal box.

A molten metal temperature sensor according to a third aspect of the present invention is a molten metal temperature sensor improved from the first aspect of the present invention. As shown in FIG. The outer coating of the high melting point composite protective tube 4 through the antioxidant layer 11 and the outer coating first layer 10a and The main constitution is to have a plurality of layers including the outer coating second layer 10b (this point is different from the first invention).
Note that FIG. 3 is a cross-sectional view enlarging and showing only a main part, and a thermocouple, an alumina insulating tube, an alumina protective tube, and the like are omitted.

A molten metal temperature sensor according to a fourth aspect of the present invention is a molten metal temperature sensor improved from the second aspect of the present invention. As shown in FIG. -The outer coating of the high melting point composite protective tube 4 and the outer coating first layer 10a and the outer coating first layer 10a and Having a plurality of outer coating second layers 10b
(This point is different from the third invention) is the main configuration. Note that this configuration is the same as that of the third invention.

Further, in the fourth invention, as in the second invention, the refractory sleeve 5 is provided in the vicinity of the high melting point composite protective tube 4 immersed in the slag.
The refractory sleeve 5 has a plurality of layers of the antioxidant first layer 11a and the coating 6c (or the antioxidant second layer 11b) on the outer surface thereof. This is a main configuration and is different from the second and third inventions in this respect. Note that FIG. 4 is a cross-sectional view enlarging and showing only a main part, and a thermocouple, an alumina insulating tube, an alumina protective tube, and the like are omitted.

In the molten metal temperature sensor according to the first to fourth aspects of the invention, the high melting point composite protective tube 4 has a shape, as shown in FIGS. It is possible to use the one described in "
It is more preferable to use a pipe-shaped one-end closed tube whose one end is sealed with ceramics cement as shown in FIG. As the above-mentioned ceramic cement, at least one kind of aggregate of Al ₂ O ₃ , MgO, MgO.Al ₂ O ₃ and
It is preferably composed of a binder of a partial hydrolyzate containing Si alkoxide as a main component.

The reason for this is that "a tube closed at one end" (see FIGS. 1 and 2) made of the same material, and a pipe-shaped tube whose both ends are open and one end of which is sealed with the above-mentioned cement. The "tube" (see Fig. 5) is difficult to manufacture with the former "closed-end tube", while the latter "closed-end tube" uses a pipe-like tube and closes one end with the above-mentioned cement. Because it can be manufactured by a relatively inexpensive means,
Also, Si alkoxide containing no alkali is used as a binder.
This is because by using the cement described above, it is possible to obtain a one-end closed type tube that has excellent corrosion resistance and that is firmly bonded to the high melting point composite protective tube 4. For the "binder of the partial hydrolyzate mainly composed of Si alkoxide", refer to the following.

The material (composition) of the high melting point composite protective tube 4 is not particularly limited in the present invention (first invention to fourth invention), but (1) ZrB ₂ content is 70 wt% or more. Sintered boride, (2) Mo-ZrO with ZrO ₂ content of 15-35 wt%
₂ system cermet, (3) BN-Al with BN content of 50 wt% or more
It is preferably made of any one of N-based nitride sintered bodies.

The above (1) "Boride sinter having ZrB ₂ content of 70 wt% or more" has excellent corrosion resistance to molten metal, and has high strength, heat resistance and thermal conductivity. Is excellent,
In addition, the above (2) "ZrO ₂ content is 15 ~ 35 wt% Mo-Z
"rO ₂ -based cermet" is a composite refractory material consisting of Mo, which has excellent heat resistance and spooling resistance, and ZrO ₂ , which has excellent heat resistance and corrosion resistance. −
It has a ring property, and in addition, the BN content of (3) above is 5
A BN-AlN nitride sintered body of 0 wt% or more "has characteristics that combine the" dilution of wettability with molten metal "of the BN component and the" melting resistance "of the AlN component. Therefore, all of them are suitable as the high melting point composite protective tube 4 in the present invention (first invention to fourth invention).

However, the above-mentioned sintered bodies (1) to (3) are
Despite the advantages described above, as explained in the section "Problems to be solved by the invention", they are both oxidizable against oxygen in molten steel, oxygen in atmosphere and oxygen in slag. Therefore, it cannot withstand long-time temperature measurement.

Therefore, in the molten metal temperature sensor according to the present invention (first invention to fourth invention), in order to solve the above-mentioned drawbacks, in order to solve the above-mentioned drawbacks, the high melting point composite protection made of the materials as described in (1) to (3) A specific ceramic coating on the inner and outer surfaces of the tube, namely "one of ZrO ₂ aggregate containing ZrO ₂ aggregate, Y ₂ O ₃ , CaO or MgO.
A coating material (hereinafter abbreviated as "ZrO ₂ -based coating material") containing a partial hydrolyzate mainly composed of Si alkoxide as a binder is provided. In addition, this ZrO ₂ -based coating material is used for the “inner coating 6” shown in FIGS.
a, outer coating 6b, coating 6c, outer coating first layer 10a, outer coating second layer 10b "
Is a covering material.

The above ZrO ₂ type coating material will be described in detail. The present inventors have found that before the present invention, “Si alkoxide,
Inorganic heat-resistant composition containing a composite alkoxide partially hydrolyzed sol composed of at least one selected from Ti alkoxide, Al alkoxide and Zr alkoxide "is proposed.
(See JP-A-1-297471). This composite alkoxide partially hydrolyzed sol is self-hardening at room temperature, and this paste-like composition suppresses shrinkage at the time of curing even if the film is thick, and has a film thickness of 500 μ (0.5 mm) or more. However, it is an adhesive that does not crack and can be firmly bonded.

Further, the inorganic heat-resistant composition obtained by mixing the composite alkoxide partially hydrolyzed sol with the refractory aggregate is used as the refractory aggregate, such as oxides of SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ and SiC. When carbides, nitrides such as Si ₃ N ₄ and BN are used, heat resistance, acid resistance, alkali resistance, electrical insulation and thermal conductivity can be imparted.

As a result of further research on the above-mentioned proposed inorganic heat-resistant composition, the present inventors have found that the inorganic heat-resistant composition is used as a coating material for a high melting point composite protective tube, that is, ZrO ₂ system. dressing "ZrO ₂ aggregates, Y ₂ O _3, binder partial hydrolyzate mainly containing at least one and Si alkoxide ZrO ₂ aggregates containing CaO or MgO - the dressing to" refractory composite protect By coating the inner and outer surfaces of the tube, the drawbacks of the high melting point composite protective tube described above can be eliminated, and it has oxidation resistance against oxygen in molten steel, oxygen in the atmosphere and oxygen in slag, and The present invention has been completed by discovering that it is possible to provide a temperature sensor for molten metal which has corrosion resistance to molten metal and can stably measure temperature continuously for a long time.

In the present invention (first to fourth inventions), the ZrO ₂ aggregate used is ZrO ₂ containing Y ₂ O ₃ , CaO or MgO.
And several types of powders with different particle sizes of 300 μm or less
It is desirable to mix (2-4 types). If only one type of fine particles of several μm is used, it is difficult to thickly coat when dried after coating, and if only one type of aggregate of about 1 to 3 μm is used, a dense film cannot be obtained and ZrO is produced by a slight impact. ₂ Particles fall off. Therefore, it is preferable to combine several kinds of aggregates having different particle sizes because a coating film that can be thickened and is structurally strong can be obtained.

The ratio of aggregate to binder is limited by the application means. For example, when applying with a trowel, spatula, etc., it is desirable to use 10 to 15 parts by weight of binder with respect to 100 parts by weight of ZrO ₂ aggregate. If the binder content is less than 10 parts by weight, the fluidity as a coating agent is poor and the fixing strength is also lowered, which is not preferable. On the other hand, in the case of brushing, spraying, dipping, etc., the binder is preferably 30 to 50 parts by weight with respect to 100 parts by weight of ZrO ₂ aggregate. 50
If the amount is over 30 parts by weight, the precipitation of ZrO ₂ will be remarkably accelerated, the uniformity of the coating film will be deteriorated, and the protective function will be deteriorated.On the other hand, if it is less than 30 parts by weight, the application by brushing, spraying or dipping becomes difficult. Not preferable.

In the present invention (1st to 4th inventions), the reason for using "ZrO ₂ aggregate" as the aggregate is that the present invention relates to the temperature sensor for molten metal. It is desirable to use refractory materials with high thermal conductivity. From this point, it can be said that MgO, Al ₂ O ₃ , MgO.Al ₂ O ₃ etc. are superior, but SiO ₂ , CaO, FeO etc. This is because when the slag contained in a large amount is in contact, the slag resistance is not good as compared with the refractory mainly containing ZrO ₂ . ZrO ₂ aggregates include Y ₂ O ₃ stabilized ZrO ₂ and CaO stabilized Z
Either rO ₂ or MgO-stabilized ZrO ₂ can be used, but especially Y ₂
O ₃ stabilized ZrO ₂ aggregate is more preferable because it has excellent corrosion resistance against slag.

In the present invention (first to fourth inventions), the thickness of the inner coating (corresponding to "inner coating 6a" in FIGS. 1 to 5) of the high melting point composite protective tube is as follows. , 0.1 to 0.5 mm is preferable, more preferably 0.2 to 0.4 mm
Is. With such a coating thickness,
It is possible to suppress "oxidation by oxygen in the atmosphere" on the inner surface of the high melting point composite protective tube.

The thickness of the outer coating of the high melting point composite protective tube (corresponding to the "outer coating 6b" in FIGS. 1, 2 and 5) is preferably 0.1 to 3.0 mm, more preferably It is preferably 0.7 to 1.5 mm. Thereby, "oxidation by oxygen in the atmosphere" and "erosion by molten steel or slag" on the outer surface of the high melting point composite protective tube can be suppressed.
If this coating thickness exceeds 3.0 mm, cracks will often occur during drying, and since the thermal conductivity is low,
It is not preferable because the response becomes poor. The coating thickness can be reduced only at the outer tip of the high melting point composite protective tube to suppress the decrease in thermal conductivity, which is also included in the present invention.

In the present invention, a desired molten metal temperature sensor can be obtained only by coating the above-mentioned ZrO ₂ type coating material on the inner and outer surfaces of the high melting point composite protective tube 4 (first invention: FIG. 1)) and a protective layer provided in the vicinity of the high melting point composite protective tube 4 immersed in the slag (second invention: see FIG. 2). For this protective layer, carbon is 10-40
It is preferable that the refractory sleeve 5 contains wt% and is made of at least one of ZrO ₂ , Al ₂ O ₃ and MgO. "Erosion and oxidative consumption" can be further suppressed, and the life of the molten metal temperature sensor can be extended.

In the case of the second invention in which the protective layer (refractory sleeve 5) is thus provided, since carbon is contained in the protective layer, oxidation and erosion proceed, so that the protective layer is protected. the ZrO ₂ based coating materials having the same composition as described above to the surface co - it is necessary to coating (in FIG. 2 "co - coating 6c" reference). In this case, the coating thickness is preferably 0.1 to 3.0 mm, more preferably 0.7 to 1.5 mm.

A molten metal temperature sensor according to the second aspect of the present invention.
In FIG. 2, cement 7 can be interposed between the outer coating 6b of the high melting point composite protective tube 4 and the refractory sleeve 5. The cement 7 is preferably a ceramic cement containing an aggregate having a high melting point such as Al ₂ O ₃ , MgO, MgO.Al ₂ O ₃ and ZrO ₂ . Since this cement 7 is used to bond and fix the refractory sleeve 5 and the high melting point composite protective tube 4 having the outer coating 6b, both refractory materials (the refractory sleeve 5 and the outer side) are protected. What is suitable for the expansion of the coating 6b) is good.

In the present invention, a desired molten metal temperature sensor can be obtained only by coating a ZrO ₂ type coating material on the inner and outer surfaces of the high melting point composite protective tube (first invention: FIG. 1).
"Inner coating 6a, outer coating 6b"), the outer surface of the high melting point composite protective tube is coated with a ZrO ₂ type coating material.
After coating (see “Outer coating first layer 10” in FIG. 3).
(corresponding to "a"), and by coating an antioxidant containing frit (corresponding to "antioxidant layer 11" in FIG. 3), a desired molten metal temperature sensor can be obtained.
(Third invention: see FIG. 3).

The third aspect of the present invention is an improvement of the first aspect of the present invention. Generally, the outer surface of the high melting point composite protective tube is fragile by being oxidized by oxygen in the atmosphere above the slag surface. It becomes a chemical conversion layer and becomes thinner than the surface. However, as in the third aspect of the invention, the antioxidant action is remarkably improved by compounding the frit-containing antioxidant. However, since the oxidation preventing member is likely to be erosion against slag, the outer surface of the refractory composite protective tube in contact with the slag, as shown in FIG. 3, further ZrO ₂ based on the antioxidant material layer 11 By coating with a covering material (see the outer coating second layer 10b), this melting damage can be prevented.

The action of the second layer of antioxidant (antioxidant layer 11) in the third invention is as follows.
(Outer coating first layer 10a and outer coating second layer 10a
Adhesive with layer 10b) and cushioning against heat,
Therefore, it is possible to prevent the ZrO ₂ -based coating material layers forming the first layer and the third layer from peeling off. In the third invention, the thickness of the antioxidant of the second layer (antioxidant layer 11) is 0.
It is preferably 2 to 1.0 mm, and more preferably 0.3 to 0.8 mm.

As the antioxidant used in the third invention,
Antioxidants for carbon-containing refractories previously proposed by the present inventors
(See Japanese Patent Publication No. 35709/1993). This antioxidant was obtained by blending powder: 100 parts by weight of an aggregate: 50-90 parts by weight, frit: 10-50 parts by weight, with a compound alkoxide partial hydrolysis sol: 35-60 parts by weight. It is a thing.

As the aggregate, feldspars such as orthoclase, potassium feldspar, and anorthite, porcelain scraps such as high-voltage insulator scraps and low-pressure insulator scraps can be used, and frit is borosilicate. A system frit, a lead borosilicate frit, a lead borosilicate frit, and an alumina borosilicate soda frit can be used. As the complex alkoxide partial hydrolysis sol, Si alkoxide and Ti
A partial hydrolyzate containing Si alkoxide as a main component and containing at least one selected from alkoxide, Al alkoxide and Zr alkoxide can be used.

In the present invention, as in the second invention,
A protective layer (refractory sleeve 5) is provided in the vicinity of the high melting point composite protective tube 4 near the slag, and a ZrO ₂ type coating material is coated on the outer surface of this protective layer (coating 6c) to obtain the desired material. Although a molten metal temperature sensor can be obtained (see FIG. 2), an antioxidant containing a frit having the above composition on the outer surface of the protective layer (refractory sleeve 5) as shown in FIG. First layer
A desired temperature sensor for molten metal can be obtained by providing the coating 6c of the ZrO ₂ type coating material via 11a.
(4th invention).

The fourth aspect of the present invention is an improvement of the second aspect of the invention. Since the protective layer (refractory sleeve 5) has pores, it has good adhesion to the antioxidant. From a certain point, in the fourth invention, as shown in FIG. 4, first, the frit-containing antioxidant described above is coated (antioxidant first layer 11a) to form a protective layer (refractory sleeve 5). The anti-oxidant is made to dig into the surface, and then the anti-oxidant
The surface of the layer 11a is coated with a ZrO ₂ type coating material (see coating 6c).

The fourth invention will be further described. The protective layer (the refractory sleeve 5) is located on the slag line and comes into contact with the slag. Therefore, in the fourth invention, ZrO ₂ having slag resistance is used. A system coating material is coated on the surface of the antioxidant first layer 11a. And, the ZrO ₂ based coating material is a protective layer.
Since the thermal expansion is smaller than that of the (fireproof sleeve 5) and the frit-containing antioxidant, the coating material is apt to crack due to the difference in expansion and contraction. In the fourth invention, the antioxidant and the multilayer are used. Thereby, the adhesiveness and the cushioning property can be obtained, and the coating film can be prevented from falling off, and the slag can be prevented from entering. This is an improvement of the second invention in this respect.

In the fourth invention, as shown in FIG.
On the outer surface of the refractory sleeve 5, an antioxidant first layer 11a and a ZrO ₂ -based coating 6c can be provided, and an antioxidant second layer 11b can be further provided thereon. As a result, it is possible to obtain a molten metal temperature sensor capable of continuously measuring temperature continuously over a long period of time.

[0049]

EXAMPLES Examples of the molten metal temperature sensor according to the present invention (first to fourth inventions) will now be described with reference to FIGS.
However, the present invention is not limited to the following examples.

(Examples 1 to 4) Of Examples 1 to 4,
Embodiments 1 and 2 are embodiments of the first invention in which the refractory sleeve 5 is not provided (see FIG. 1), and Embodiments 3 and 4 are
Is an embodiment of the second invention in which a refractory sleeve 5 is provided (see FIG. 2).

In Examples 1 to 4, the alumina protective tube 3 having a diameter of 12 mmφ and an inner diameter of 8 mmφ was used. As the high melting point composite protective tube 4, in Examples 1, 2 and 4, the "one-end closed tube" (see FIGS. 1 and 2) made of the same material having a diameter of 25 mmφ and an inner diameter of 15 mmφ was used. On the other hand, Example 3
Then, a "one-end closed pipe" (see FIG. 3) having a diameter of 25 mmφ and an inner diameter of 15 mmφ, the lower end of which was sealed with cement 7 for 10 mm was used. This cement 7 is MgO with a particle size of 44μ or less.
It is a ceramic cement consisting of Al ₂ O ₃ : 85 wt% and a composite alkoxide partial hydrolyzate of Si and Ti alkoxide with Si / Ti of 100/10: 15 wt%.

The inside and outside coatings 6a and 6b of the high melting point composite protective tube 4 are made of ZrO ₂ (Y
₂ O ₃ : 8 wt% included: 75 wt%, Si / Ti 100/10 Si / Ti alkoxide compound alkoxide partial hydrolyzate: 25 wt% ZrO ₂ type coating material (hereinafter referred to as “coating material (ZrO ₂ System) ”). The composition (wt%) of the high melting point composite protective tube 4 and the thickness (mm) of the inner and outer coatings 6a, 6b of the protective tube 4 in each example are shown in Table 1 below.

In the third and fourth embodiments, the refractory sleeve 5 (see FIG. 2) has an outer diameter of 55 mm and an inner diameter of 28.
mm, Al ₂ O ₃ : 65 wt%, SiC: 5 wt%, C: 30 wt%
The Al ₂ O ₃ -C system consisting of As the coating 6c (see FIG. 2) of the refractory sleeve 5, a coating material (ZrO ₂ system) having the same composition as that of the coatings 6a and 6b was used.

In Examples 1 and 2, the high melting point composite protective tube having the composition (wt%) shown in Table 1 below was used, and the inner coating thickness and the outer coating thickness shown in Table 1 were also used. A temperature sensor for molten metal having Furthermore, in Examples 3 and 4, as also shown in Table 1, an Al ₂ O ₃ -C-based refractory sleeve and a coating material (ZrO ₂₎ having the same composition as the coating material on the surface thereof were used. Each of the systems was coated with a thickness of 1.5 mm (see coating 6c in FIG. 2) to produce a molten metal temperature sensor.

The temperature sensor for molten metal produced in the above Examples 1 to 4 was immersed in molten steel at 1550 ° C. to measure the temperature. The service life (index) at this time was measured, and the results are shown in Table 1. In addition, the service life (index) means the temperature sensor for molten metal produced in Comparative Example 3 described later, and the slag hot water surface portion is corroded and oxidized to reduce the wall thickness of the protective tube, making it impossible to measure the breakage temperature. It is expressed as an index for the service life up to 1.

(Examples 5 to 7) Of the present Examples 5 to 7,
Examples 5 and 6 are examples of the third invention in which the refractory sleeve 5 is not provided (see FIG. 3), and Example 7 is of the fourth invention in which the refractory sleeve is provided. This is an example (see FIG. 4).

In Examples 5 to 7, the high melting point composite protective tube 4 having the composition shown in Table 1 below was used, and the inner layer (inner coating 6a) of the high melting point composite protective tube 4 and the outside As the first layer (outer coating first layer 10a) and the third layer (outer coating second layer 10b), the coating material (ZrO ₂ system) used in Examples 1 to 4 was used. , As the second layer (antioxidant layer 11), "frit: 30 wt%, porcelain scrap powder: 50 wt
%, Potassium feldspar powder: 20 wt% Si / Ti 100/10 Si
A composite alkoxide partial hydrolyzate of alkoxide and Ti alkoxide: an antioxidant of 44 wt% was used. The coating thickness of each layer is shown in Table 1 below.

Example 7 is an example in which an Al ₂ O ₃ -C refractory sleeve 5 similar to those in Examples 3 and 4 is provided, and the above-mentioned composition is used as the first layer on the surface thereof. A first layer 11a of an antioxidant, a second layer (coating 6c) of a coating material (ZrO ₂ system), and a third layer of the same composition of an antioxidant.
11b was coated. The coating thickness of each layer is shown in Table 1 below.

With respect to the temperature sensor for molten metal produced in the above Examples 5 to 7, the service life was the same as in Examples 1 to 4 above.
(Index) was measured, and the results are shown in Table 1.

[0060]

[Table 1]

Comparative Example 1 For comparison with Examples 1 and 5 above, a BN-based protective tube having no coating layer on the inner and outer surfaces (same composition as Examples 1 and 5: see Table 2). A temperature sensor for molten metal using was manufactured. Then, the service life (index) was measured in the same manner as in the above example, and the results are shown in Table 2.

(Comparative Example 2) For comparison with Examples 2 and 6, the conventional molten metal temperature sensor of (1), that is, "Z"
A temperature sensor for molten metal comprising an rB ₂ system body (composition: see Table 2), an oxide layer on the inner surface of the body, a glass layer on the outer surface, and an inorganic fiber layer on the outer surface of the glass layer. With respect to JP-A-1-321326), in the same manner as in the above embodiment,
The service life (index) was measured and the results are shown in Table 2.

(Comparative Example 3) For comparison with the above-mentioned Examples 3, 4 and 7, Mo having no coating layer on the inner and outer surfaces.
-ZrO ₂ based protective tube: using (composition see Table 2), and Al ₂ O ₃ -
A temperature sensor for molten metal provided with a C-based refractory sleeve (the same refractory sleeve as in Examples 3, 4 and 7) was prepared, and the durability time (index ) Was measured and the results are shown in Table 2.

[0064]

[Table 2]

Comparing Examples 1 and 5 with Comparative Example 1,
As is clear from the comparison between Tables 1 and 2, in the BN-based protection tubes having the same composition, in Examples 1 and 5 in which the coating layer specified in the present invention was provided on the inner and outer surfaces, the service life was
The (index) was "0.5, 0.8", whereas in Comparative Example 1 which did not have such a coating layer, it was "0.3" and temperature measurement was impossible in an extremely short time. Further, comparing Examples 2 and 6 with Comparative Example 2, in Examples 2 and 6 in which the coating layers specified in the present invention are provided on the inner and outer surfaces, the service life (index) is "0.9, 1.3". On the other hand, in the conventional molten metal temperature sensor of (1) (Comparative Example 2), it was confirmed to be "0.5".

From Tables 1 and 2, the inner and outer surfaces were
In the case of using a Mo-ZrO ₂ type protective tube having no coating layer, even if an Al ₂ O ₃ -C type refractory sleeve is provided,
The service life (index) is 1 (Comparative Example 3), and in Examples 3, 4 and 7 corresponding to this, more than "1.4, 1.8, 2.
4 "was recognized. As described above, it was confirmed that by providing the coating layer specified in the present invention on the inner and outer surfaces, it is possible to stably measure the temperature continuously for a long time.

[0067]

As described in detail above, the temperature sensor for molten metal according to the present invention includes: -the inner and outer surfaces of a high melting point composite protective tube, or a protective layer.
The outer surface of the (refractory sleeve) was replaced with "ZrO ₂ aggregate, Y ₂ O ₃ , CaO.
Alternatively, one of ZrO ₂ aggregates containing MgO and a coating material containing a partial hydrolyzate mainly composed of Si alkoxide as a binder are coated (first invention, second invention
Inventive), and, further, a coating layer comprising the above-mentioned coating material is provided via a coating layer comprising "an antioxidant containing an aggregate and frit-containing powder and a complex alkoxide partial hydrolysis sol as a binder". (Third and fourth inventions), which has oxidation resistance to oxygen in molten steel, oxygen in atmosphere and oxygen in slag, and corrosion resistance to molten metal, It is possible to provide a molten metal temperature sensor capable of stably and continuously measuring temperature over time.

[Brief description of drawings]

FIG. 1 is a temperature sensor for molten metal according to an embodiment of the first invention.
Sectional view of.

FIG. 2 is a temperature sensor for molten metal according to an embodiment of the second invention.
FIG.

FIG. 3 is a molten metal temperature sensor according to an embodiment of the third invention.
Sectional view of.

FIG. 4 is a temperature sensor for molten metal according to an embodiment of the fourth invention.
FIG.

FIG. 5 is a cross-sectional view showing another embodiment of the high melting point composite protective tube which constitutes the temperature sensor for molten metal according to the present invention (first invention to fourth invention).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Thermocouple 2 Alumina insulation tube (with thermocouple) 3 Alumina protection tube 4 High melting point composite protection tube 5 Refractory sleeve 6a Inner coating (for inner surface of high melting point composite protection tube) 6b Outer coating ( 6c Coating (for protective sleeve) 7 Cement 8 Stainless steel protection tube 9 Terminal box 10a Outer coating 1st layer 10b Outer coating 2nd layer 11 Antioxidant Layer 11a Antioxidant first layer 11b Antioxidant second layer

Front page continued (72) Inventor Kazuhisa Tanaka 1-1, Tobata-cho, Tobata-ku, Kitakyushu, Fukuoka Inside Nippon Steel Co., Ltd. Yawata Works (72) Inventor Seiichi Takahashi 1-Hibata-cho, Tobata-ku, Kitakyushu, Fukuoka No. 1 Nippon Steel Co., Ltd., Yawata Works (72) Inventor Yoji Fujii 134-132 Minamikoto, Okayama City, Okayama Prefecture (72) Inventor Hiroshi Minamizono 256-11 Iron, Okayama City, Okayama Prefecture (72) Inventor Kiyomi Taniguchi 1425-5 Mitsuishi, Bizen City, Okayama Prefecture (72) Inventor Ichiro Taniuchi 3-1-1-18-103 Moritsune, Kokuraminami-ku, Kitakyushu City, Fukuoka Prefecture

Claims (11)

[Claims] 1. A molten metal temperature sensor comprising an alumina protective tube containing a thermocouple and a high melting point composite protective tube fitted to the outside of the alumina protective tube, wherein the inner and outer surfaces of the high melting point composite protective tube are A temperature sensor for molten metal, characterized by being coated with a coating material containing at least one refractory aggregate of oxides, carbides and nitrides and a partial hydrolyzate mainly composed of Si alkoxide as a binder. . 2. A molten metal temperature sensor comprising an alumina protective tube containing a thermocouple and a high melting point composite protective tube fitted to the outside of the alumina protective tube, wherein the inner and outer surfaces of the high melting point composite protective tube are ZrO ₂ aggregate, ZrO ₂ containing Y ₂ O ₃ , CaO or MgO
A temperature sensor for molten metal, characterized in that it is coated with a coating material containing at least one kind of aggregate and a partial hydrolyzate mainly composed of Si alkoxide as a binder. 3. A molten metal having an alumina protective tube containing a thermocouple, a high melting point composite protective tube fitted to the outside of the alumina protective tube, and a protective layer provided in the vicinity of the slag immersion of the high melting point composite protective tube. In the temperature sensor for use, the inner and outer surfaces of the high melting point composite protective tube and the outer surface of the protective layer are formed of ZrO ₂ aggregate, Y ₂
A temperature sensor for molten metal, characterized in that it is coated with at least one ZrO ₂ aggregate containing O ₃ , CaO or MgO and a coating material containing a partial hydrolyzate mainly composed of Si alkoxide as a binder. -. 4. A molten metal temperature sensor comprising an alumina protective tube containing a thermocouple and a high melting point composite protective tube fitted to the outside of the alumina protective tube, wherein the inner surface of the high melting point composite protective tube is ZrO ₂ aggregate, ZrO ₂ containing Y ₂ O ₃ , CaO or MgO
After coating with a coating material containing at least one kind of aggregate and a partial hydrolyzate mainly composed of Si alkoxide as a binder, while coating the outer surface of the high melting point composite protective tube with the coating material, Further, a temperature for molten metal characterized in that a plurality of layers are coated alternately with an antioxidant containing the aggregate and the frit-containing powder and a partial hydrolyzate mainly composed of Si alkoxide as a binder, and the coating material. Sensor. 5. A molten metal having an alumina protective tube containing a thermocouple, a high melting point composite protective tube fitted to the outside of the alumina protective tube, and a protective layer provided in the vicinity of the slag immersion of the high melting point composite protective tube. use temperature sensors - in the inner surface of the refractory composite protective tube, comprising ZrO ₂ aggregates, the Y ₂ O _3, CaO or MgO Zr
At least one kind of O ₂ aggregate and a partial hydrolyzate containing Si alkoxide as a main component were coated with a coating material, while the outer surface of the high melting point composite protective tube was coated with the coating material. After that, further, a plurality of layers are coated alternately with an antioxidant containing the aggregate and frit-containing powder and a partial hydrolyzate mainly composed of Si alkoxide as a binder, and the coating material. A temperature sensor for molten metal, characterized in that the surface is coated with the antioxidant and then coated with the coating material, or further coated with the antioxidant. 6. The protective layer according to claim 3 or 5 is a card.
The molten metal temperature sensor according to claim 3 or 5, characterized in that it comprises a refractory sleeve containing 10 to 40 wt% of bon and containing at least one of ZrO ₂ , Al ₂ O ₃ and MgO. 7. The antioxidant according to claim 4 or 5,
Powder consisting of 50 to 90 parts by weight of aggregate and 10 to 50 parts by weight of frit
The temperature sensor for molten metal according to claim 4 or 5, wherein 100 to parts by weight of 35 to 60 parts by weight of a partial hydrolyzate mainly composed of Si alkoxide is added. 8. The high melting point composite protective tube according to claim 1, 2, 3, 4 or 5, (1) a boride sintered body having a ZrB ₂ content of 70 wt% or more, (2) ZrO ₂ Mo-with a content of 15-35 wt%
ZrO ₂ system cermet, (3) BN content is 50 wt% or more
The molten metal temperature sensor according to claim 1, 2, 3, 4, or 5, which is made of one of an AlN-based nitride sintered body. 9. The high melting point composite protective tube according to claim 1, 2, 3, 4 or 5, wherein the ZrO ₂ content is 15 to 35 wt%.
2. A ZrO ₂ -based cermet, wherein
The temperature sensor for molten metal according to 2, 3, 4 or 5. 10. The high melting point composite protective tube according to claim 1, 2, 3, 4, or 5 is a closed tube with one end made of the same material or a closed tube with one end sealed with a ceramic cement. Claims 1, 2, 3, 4
Alternatively, the temperature sensor for molten metal according to 5. 11. The ceramic cement according to claim 10, wherein at least one aggregate of Al ₂ O ₃ , MgO, and MgO.Al ₂ O ₃ and a binder of a partial hydrolyzate mainly containing Si alkoxide are used. The molten metal temperature sensor according to claim 10, wherein: