UA124020C2 - Fire-resistant plating for sliding nozzle, and method of manufacturing same - Google Patents

Abstract

The present invention provides a fire-resistant plating that inhibits the occurrence of surface damage on a sliding surface when receiving steel having an especially low free oxygen concentration in a melt, such as Al-killed steel. The fire-resistant plating of the present invention contains 15 % by mass to 45 % by mass of an Al4O4C component, 2.0 % by mass to 4.5 % by mass of a free carbon component, 0.5 % by mass to 4.0 % by mass of an SiO2 component, and 1.0 % by mass or less (inclusive of 0) of a metallic aluminum component, the main component of the remainder being an Аl2О3 component as a main component. The plating includes a surface that serves as a sliding surface, and has a permeability of 40×10-17 m2 or less in a direction orthogonal to said surface sewing as a sliding surface, and an apparent porosity of 11.0 % or less.

Description

FIELD OF THE INVENTION

0001

The present invention relates to a refractory material for a sliding nozzle plate (hereinafter also referred to as "the plate") for use in controlling the opening and closing, as well as in controlling the pouring rate in the process of issuing molten steel, in particular molten steel having a low concentration of free oxygen , from a container such as a ladle or intermediate ladle; in the steelmaking process, and to the method of obtaining refractory material.

TECHNICAL LEVEL

OOO2I

Surface pitting of the sliding surface, which is one of the main types of plate damage, is a phenomenon where the structure of the sliding surface, which serves as the working surface during casting, is embrittled, resulting in secondary phenomena such as abrasion, wear and chipping. It is believed that this surface cracking is due to the complex effect of several factors, such as chemical factors and physical factors. Oxidation and decarburization are believed to often initiate surface embrittlement, with oxidation caused by gas-phase oxidation by oxygen in atmospheric air and liquid-phase oxidation by oxygen in molten steel, and decarburization caused by desorption of carbon into molten steel. It is also believed that molten steel or components of molten steel, such as inclusions and slag, infiltrate into, adhere to, or react with the structure of the work surface, which is embrittled by oxidation and decarburization, and then the resulting infiltrated or adhered layer causes spalling of the structure, resulting in acceleration surface cracking.

IO0OZI

At the same time, data on oxidation and decarburization mechanisms other than simple gas-phase oxidation, liquid-phase oxidation due to oxygen in molten steel, and decarburization due to desorption of carbon into molten steel have recently appeared.

For example, the following Non-Patent Document 1 describes a test in which three types of steel consisting of ultra-low carbon AI-deoxidized steel (carbon concentration: 20 ppm), low-carbon AI-deoxidized steel (carbon concentration: 410 ppm) and

From ultra-low-carbon deoxidized 5i-em steel (carbon concentration: 20 ppm) was placed in an electric furnace and subjected to a reaction with a simple sample consisting of a finely dispersed powder of aluminum oxide and carbon, at a temperature of 1560 C in an Ag atmosphere with vacuum replacement, as well as evaluated and examined the interphase structure of the sample. As a result of the reaction with ultra-low-carbon deoxidized AI steel (carbon concentration: 20 ppm), the formation of a crumbly layer with a thickness of about 200 μm on the working surface of the sample was established, that is, the release of carbon grains and A/2O3z. Similarly, in low-carbon AI-deoxidized steel (carbon concentration: 410 ppm), the formation of a crumbly layer with a thickness of about 100 microns was established, from which carbon grains and AIgOzAI were released.

In addition, in the following Non-Patent Document 2, after a molten steel pouring operation, such as AI deoxidized steel having a low concentration of free oxygen, the sliding surface of the plate was observed to find out the formation of a crumbly layer from which carbon grains were released and A/2O3. 0004)

As stated above, during the pouring operation of molten steel, such as AI1-deoxidized steel having a low concentration of free oxygen, it is believed that the embrittlement layer is formed in the part of the sliding surface of the plate in contact with the molten steel or on the surface of the plate subjected to the influence of the inner space of the hole (this surface will be called the "working surface" of the plate in the future), thereby leading to the appearance of the phenomenon of surface cracking. However, the detailed mechanism, method of improvement, etc., for surface cracking have not been sufficiently studied.

LIST OF CITATIONS

UNPATENT DOCUMENTS

IO0O5I

Non-Patent Document 1: Rgtoseedipudb5 oi She 151 gop apa 5iee!i Veigasioies Sottievje,

Mometreg" 21, 2013, p. 180 - p. 187.

Non-patent Document 2: Rgoseeeeedipud5 oi She Zgy gop apa 5iev! Veigtasupevz Sottiinevie,

Mometreg 26, 2015, p. 167 - p. 174.

BRIEF DESCRIPTION OF THE ESSENCE OF THE INVENTION

(510) TECHNICAL PROBLEM

IO0Ob)

The technical problem to be solved by the present invention is to provide a refractory material for the plate capable of allowing the sliding surface of the plate to become less prone to surface pitting during the pouring operation of molten steel, such as deoxidized A1 steel, and a method of obtaining the refractory material for the plate.

In addition, the technical problem to be solved by the present invention is to provide a refractory material for the plate which is suitable for the pouring operation of molten steel having a low concentration of free oxygen, and a method for obtaining the refractory material for the plate. |Solving a technical problem) 00071

As a result of various studies by the inventor of the mechanism of surface cracking on the sliding surface during the pouring operation of molten steel, such as AI-deoxidized steel, in particular molten steel having a low concentration of free oxygen, it was found that the above-mentioned embrittlement layer from which the grains were released carbon and A/I2Oz, formed as a result of the redox reaction between carbon and oxide, etc. in the refractory material, and surface spalling is accelerated when the spalled layer is damaged.

IO0O8)I

More specifically, the carbon in the refractory is oxidized by the oxygen (0) in the component

AI29Oz, component 510", component 2gO"5, etc., which are the main components in the refractory material, and becomes a gas phase in which CO gas is released, thereby causing decarburization. In addition, the AI2Oz component, the 5iO2 component, the 27O»2 component, etc. are reduced by carbon with the formation of gas-phase particles such as AI gas, AI2O gas, 510 gas, and carbides such as 2, 5iC, etc. . It is believed that many of the gas-phase particles formed move to the working surface and desorb into the molten steel. In addition, it is believed that part of the 5iO gas forms 5iC in the refractory structure and similarly forms 2gC, while when the carbide is formed from the oxide, its volume decreases and many voids are formed in the refractory structure adjacent to the working surface, with the formation of a brittle layer .

ИО0О9

In addition, in the inner hole of the plate during molten steel casting, when the degree of opening of the inner hole decreases, that is, the hole narrows, an area is generated that is not filled with molten steel. In this area, the degree of narrowing becomes greater, the degree of pressure reduction becomes greater. Thus, as a rule, the pouring time will be increased. It was also found that in some cases, compared to the sliding surface of the lower part of the plate, the sliding surface of the upper part of the plate, which is exposed to such a pressure reduction for a longer time, is rougher, because in the structure adjacent to the sliding surface of the upper part of the plate, the crumbly layer, from which the grains of carbon, A/2Oz, etc., have been released, becomes thicker, and the depth of penetration of molten steel or the like becomes greater.

IOO1OI

Based on these facts, the authors of the invention found that the formation of the above-described embrittlement layer or surface cracking is influenced by temperature, time and pressure in the space of the inner hole in addition to the concentration of oxygen in the molten steel. Then the inventors discovered that when the concentration of free oxygen in molten steel is 30 ppm or less, the higher the temperature, the longer the time and the greater the degree of negative pressure in the space of the inner hole, the greater the degree of formation of a brittle layer or surface cracking.

ИО0О11И

More specifically, in the refractory structure around the working surface, in addition to AI2Oz grains, a significant transformation of grain aggregates was also observed, such as raw material based on AI2Oz - 2102 and 72gO5-mullite, which added raw material with low thermal expansion. It was also found that this transformation also tends to be larger in the upper part of the plate than in the lower part of the plate when regulated by pouring over a long time. Further, it was established that in raw material based on AI2Oz-2tO" grains of 7gO:" in the raw material are transformed into 2gS, while in 7gOg2-mulite the component 5iO: in the mullite part is released, only AIg2Oz remains, the 5iOg component is gasified and migrates to the surface layer of the particle of 7gO2-mullite to exist as 5IiS. In addition, it was confirmed that not only the 5iOg2 component in the mullite part, but also the AI2Oz component is released as transformations progress. In addition, as with the 270" grains, it was confirmed that the 2702 60 grains were converted to 2gS similarly to the 2gO" grains in the AI2Oz-2gO" raw material.

0012

All these phenomena are caused mainly by the reducing action of carbon in the refractory structure, and under conditions of negative pressure, the reduction reaction of oxide components, such as 5iO", 2gO", and

AIII25Oz in the refractory structure for the plate, with carbon it progresses even more.

IOO1ZI

These mechanisms can basically be represented by the reactions shown by the following formulas from 1 to 5.

ZO" (t) i- ZS (t) -51С (t) 42С0О (g) Formula 1

ЗАИ2Оз 27510" (t) 412С (t)-ЗА2Оз (t) t251С (t) 44СОО (g) 412С (t) Formula 2 21" (t) и ЗС (t) х2гС (t) 42СО (g) Formula Z

AI2Oz (t) and ZS (t) -2AI (g) "ZSO (g) Formula 4

AI2Oz (t) 12 (t) XA2O (g) 42С0О (g) Formula 5

IOO141

As a result of calculating the reactions of these Formulas 1-5 at a temperature of 1550 "C using Rasi Zade thermodynamic calculation software, it was established that the reactions are more prone to progress under conditions of negative pressure. In addition, it was found that the reactions are more prone to progress in of the order (1)2(2)2(3)2(4)-(5), and the raw material for general use in the mentioned refractory material for the plate is prone to transformation in the order of mullite, 2gO2-mullite»AI2Oz3z-27O2»AIg2Oz. Next , according to this calculation, it was found that although the reduction reactions (4) and (5) with carbon AIg2Oz do not progress at a normal pressure of 1 atm, in the case where a small amount of component 510 is present, the reaction occurs in a very small amount from 1 atm .This shows that when the io component is contained, the above-mentioned reduction reaction also occurs on the slip surface in the region that becomes atmospheric pressure or positive pressure during pouring to form a crumbly layer, causing surface cracking. 0015)

Based on these data, the refractory material for the sliding nozzle plate of the present invention is mainly created based on the following conditions.

(1) The amount of the carbon component must be the minimum necessary. (2) The amount of the 5iO2 component and the amount of the 27O2 component must be the minimum required. (3) The amount of the metal AI component should be the minimum necessary. (4) The refractory structure should be compacted.

Here, the above term "minimum required" means approximately the minimum relative amount/degree required taking into account the balance of strength, heat resistance, corrosion resistance, etc., after using other alternative means 0016)

In addition, the refractory material for the sliding nozzle plate of the present invention contains the component Al/2Oz as a main component in addition to the component Al/I«O4C.

The AI2Oz component, in particular corundum, has the necessary properties in the most balanced way, such as corrosion resistance, wear resistance, heat resistance, thermal expansion properties, etc. Therefore, the refractory material for the sliding nozzle plate of the present invention also contains corundum as an A/2Oz component as a main component. 00171

On the other hand, when the amount of the carbon component described above (1) is reduced, the formation of a brittle layer can be restrained. However, the heat resistance deteriorates due to the increase in the modulus of elasticity or the coefficient of thermal expansion, the progress of sintering when receiving heat during casting, etc., as well as due to chipping of the edges of the plate, radial cracks, which also cause a deterioration in durability. Furthermore, when the amount of compn

ZO" and the amount of component 770" described above (2) decreases, the formation of a brittle layer can be restrained, but then heat resistance decreases and chipping of the edge of the plate occurs, radial cracks appear, etc., which also leads to a deterioration in durability. 0018)

Therefore, in this invention, heat resistance increases due to the content of the AI404C component in the amount of 15 to 45 wt. 956, which has less thermal expansion than corundum. Component

AI404C is the main component of aluminum oxycarbide composition and has a coefficient of thermal expansion of about 4x105/K, which is about half of this coefficient of corundum, and thus has a high effect of reducing the coefficient of thermal expansion. In addition, the component AIgO4C is restored in the presence of carbon, as shown in the following formula 6.

And according to the calculation at a temperature of 1550 "С with the help of Rasi 5abe it was found that the reaction of this formula 6 occurs even at 1 atm. 0019)

On the other hand, as a result of the study of the structure around the working surface after the actual use of many plates on which the aluminum oxycarbide composition was applied, it was established that a small transformed layer, which has a thickness of about several tens of micrometers, is formed only around the surface of the aluminum oxycarbide grains and a deeper structure remains less transformed. From this, it was found that the reaction represented by Formula 6 above occurs only in the surface layer of the aluminum oxycarbide composition on the surface of the work surface. Further, from the above Formula 6, it is believed that the above-mentioned converted layer consists of A/2O3 and AlI3C3, and both AlI2O3 and AlI3C3 are more stable than 2" and 5iO" in the coexistence of carbon, and therefore they are considered to be functional as a protective layer for aluminum oxycarbide composition. From this, it was found that the composition of aluminum oxycarbide has a higher stability in a reducing atmosphere at high temperature than the composition based on AI2Oz3-2gO", 2gO2-mullite and the composition based on A/203-510", and is able to retain the property of low thermal expansion for a long time, and therefore makes it difficult to embrittle the structure due to the progression of the transformation of the composition itself. 0020

Despite the fact that the metal AI component in the above condition (3) mainly has the effect of increasing strength by oxidation, it also has a strong reducing effect. The amount of metal AI component should be reduced to the minimum required for inhibition

From a reaction, preferably such as excessive oxidation, to prevent the deterioration of heat resistance and to prevent the formation of a brittle layer due to the reduction of the oxide. 00211

The above-mentioned mechanisms (reactions) pass through the pores in the refractory material, and therefore, increasing the density of the refractory structure, contribute to restraining the formation of a brittle layer or surface cracking. However, the pores are necessary to a certain extent and cannot be completely excluded from the production point of view, since the pores are also responsible for the functions of softening the thermal and mechanical stress of the refractory structure. Therefore, the sealing of the refractory structure in the above condition (4) must be adjusted from the point of view of balancing with heat resistance. 0022

The practice of impregnation with tar, pitch or thermosetting resin to supplement the carbon source and perform sealing is widespread. However, the carbon added to the refractory structure in this way is active and an excess of carbon is present, thus accelerating the formation of a brittle layer. In addition, with regard to such sealing, it can be implemented by other means, and thus, in this invention, it is desirable to dispense with such an impregnation step.

IOO23I

Based on the above conclusions, this invention is a refractory material for a sliding nozzle plate and a method of obtaining a refractory material for a sliding nozzle plate in the following points 1-6. 1. Refractory material for a sliding nozzle plate for use in steel casting, while the refractory material contains the component A/I«04C, in an amount from 15 to 45 wt. 95, a free carbon component in the amount of 2.0 to 4.5 wt. 95, 5iO" component in the amount from 0.5 to 4.0 wt. 95, as well as the metal AI component in the amount of 1.0 wt. 95 or less (including zero), the remainder comprising A/2Oz component as a major component, the refractory material comprising a sliding surface and having a gas permeability of 40x10!7 mg or less as measured for said refractory material, including said surface, and in a direction perpendicular to said surface, and an open porosity of 11.0, 96 or less.

2. The refractory material according to item 1, and the gas permeability is from 5x10-7 to 40x1077 mg, and the open porosity is from 8.0 to 11.0 95. 3. The refractory material according to item 1 or item 2, which has a coefficient thermal expansion from 0.5 to 0.6 95, measured in a non-oxidizing atmosphere at 1000 "C, and bending strength from 15 to 40

MPa, measured at room temperature. 4. The refractory material according to any one of paragraphs 1-3, in which the steel has a free oxygen concentration of 30 ppm or less, measured in the molten state of the steel during casting. 5. The method of obtaining a refractory material according to any of paragraphs 1-4, and the method includes the steps of: forming a mixture containing metal AI or AI-containing alloy, where the total amount of metal AI component in metal AI or AI-containing alloy is 2.0-10.0 wt. 9b; and subjecting the mixture to heat treatment in a non-oxidizing atmosphere at 1000 "С or more to adjust the content of the metal AI component in the refractory material within 1.0 wt. 95 or less (including zero). 6. The method according to item 5, which is carried out without a stage impregnation of refractory material with tar, pitch or thermosetting resin. 00241

In this invention, the term "free oxygen in molten steel" means dissolved oxygen in molten steel and does not include oxygen contained in inclusions in molten steel present in the form of oxide. Also, in this invention, the term "free carbon component" means a carbon component that is present alone and excludes carbon components that are present in the form of a compound with other elements, regardless of crystallinity, shape, etc.

TECHNICAL EFFECT OF THE INVENTION) (0025)

The present invention makes it possible to significantly reduce surface scratches on the sliding surface of the sliding nozzle plate when casting steel, such as deoxidized AI steel, especially even when the degree of opening is small and the degree of throttling is large, or during long-term casting. This makes it possible to obtain stable high durability.

In particular, when casting steels with a concentration of free oxygen in the molten steel of 30

Of pprt or less, which has hitherto been prone to significant damage when casting, the present invention can significantly reduce surface pitting on the sliding surface of the sliding nozzle plate. This makes it possible to obtain stable high durability.

DESCRIPTION OF IMPLEMENTATION OF THE INVENTION

(oO26)

The refractory material for the plate according to this invention contains the component A/«04C in an amount from 15 to 45 wt. 95. If the content of the AI204C component is less than 15 wt. 95, the refractory material has a low effect of reducing the coefficient of thermal expansion and has insufficient heat resistance. If the content of the AI404C component exceeds 45 mab. 9o, then the amount of thermal expansion of the refractory material for the plate becomes relatively smaller than the amount of thermal expansion of the metal strip adjacent to the outer periphery of the refractory material, which leads to a decrease in the binding force of the refractory material for the plate, and as a result, may occur or spread cracks In addition, due to the displacement of the metal strip, and especially during the repeated use of the plate, there may be problems with the deterioration of performance and safety during use, such as, for example, disconnection of the plate. (00271

The refractory material for the plate according to the present invention contains a free carbon component in an amount of 2.0 to 4.5 wt. 95. If the content of the free carbon component is less than 2.0 wt. 956, the refractory is easily wetted by oxides such as slag, so that oxide inclusions and slags in the molten steel are more likely to adhere to and penetrate the working surface of the plate and facilitate surface embrittlement.

In addition, the effect of restraining sintering between oxides deteriorates, which prevents the reduction or increase of the modulus of elasticity, so that the heat resistance deteriorates and the probability of the appearance and propagation of cracks increases. If the content of the free carbon component exceeds 4.5 wt. to, embrittlement of the structure is accelerated by the release of carbon due to oxidation in the part exposed to the outside air. In addition, according to the formulas 1 to 5 above, the oxides forming the refractory material are also released together with the carbon in the refractory structure. As a result, structural fragility will be more likely to progress and surface spalling will be facilitated. (510) (оО28)

The refractory material for the plate according to this invention contains the component 51iO" in the amount of 0.5-4.0 wt. 95. Component 5iO" contributes to the improvement of refractory strength and compaction of the structure, depending on its source material or its form of existence. Also, although the metallic A! the component contributes to the improvement of corrosion resistance and resistance to oxidation, compaction of the structure, it generates AIgSz due to obtaining heat, in particular, during casting, and as a result AIgSz hydrates in some cases destroy the structure. The 5iO component is effective for keeping AIgSz hydrated." To prevent the hydration of AI"Cz, it is necessary that component 5102 be contained in an amount of 0.5 wt. 95 or more, and if the content is less than 0.5 wt. 95, it is impossible to achieve a sufficient hydration restraining effect. On the other hand, as shown in Formulas 1 and 2, the 5iO2 component partially reacts with carbon under high temperature conditions and precipitates as 5IiC and is released as 510 (g). However, the formation of 5iC is accompanied by a decrease in volume, and therefore it is also one of the factors that deteriorate the structure. In addition, as described above, according to the calculation using Gracy Zadeh, although the reduction reactions shown in formulas (4) and (5) with carbon AI2Oz do not proceed at 1 atm., which is the normal pressure, in the case where a small the amount of the component is 510", the reaction occurs in a very small amount from 1 atm.

The AI2Oz reduction reaction is one of the factors that facilitates the embrittlement of the refractory structure. To prevent deterioration of the structure as a result of the reduction reaction or release of the 5iO2 component and the AI2Oz component, the content of the 5iOg component should be 4.0 wt. 95 or less.

IoO29

In the refractory material for the plate according to this invention, the content of the metal AI component is set at 1.0 wt. 95 or less (including zero). If the content of metal A! component is 1.0 wt. 96 or less, the refractory material contributes to the inhibition of oxidation of the free carbon component or the AI«0:C component in the refractory structure, improvement of corrosion resistance, compaction of the refractory structure, etc. without a significant change in the refractory structure due to heat generation during use. However, if the content of the metal AI component exceeds 1.0 wt. 95, it is difficult to ensure the stability of the refractory structure depending on the casting time, the type of steel, the number of applications, etc. and deterioration of durability is caused more quickly.

Co., Ltd.) IOOZOI

The rest of the refractory material for the plate according to the present invention, in addition to the other components mentioned above, consists mainly of the component AI2Oz in the form of corundum. This is because Al2Oz in the form of corundum has a melting point of 2060 "C, which is excellent for heat resistance, and has excellent corrosion resistance to foreign components such as Geo. In addition, in order to prevent oxidation, in addition to the Al2Oz component the residue may contain carbide components such as small amounts of 5iC, BaC, AlYi, Cz, etc., nitride components such as bisMy, VM, AIM, etc. and a metallic component such as metallic 5i, Ma in AI !- alloys, etc. These components also deteriorate the density of the refractory structure, corrosion resistance, etc., due to oxidation, transformations, etc., so that their total amount is preferably about 7.0 wt: 95 or less .0091)

In the refractory material for the plate of the present invention, the density of the structure is an important factor, as well as the determination of the components as described above. In particular, it is important that the structure of the sliding surface side of the plate, especially the part serving as the working surface, which is on the high temperature side and is easily affected by foreign components and has a large degree of transformations such as reduction reaction, is dense.

This density can be estimated or determined by gas permeability measured for said refractory material, including the surface serving as a sliding surface and in a direction perpendicular to said surface, and open porosity. Therefore, it is necessary that the refractory material for the plate of the present invention includes a surface serving as a sliding surface and has a gas permeability of 40x10-77 me or less as measured for said refractory material including said surface and in a direction perpendicular to said surface, and an open porosity of 11.095 or less. If gas permeability exceeds 40x1077 m? or if the open porosity exceeds 11.0 95, the decomposed gas inside the refractory material easily migrates, the further infiltration of the foreign component easily progresses, so that the deterioration of the structure of the refractory material and damage to the sliding surface (surface cracking) are accelerated. However, if the refractory structure is excessively compacted, there is a possibility that the modulus of elasticity will increase and the heat resistance will deteriorate, so that, preferably, the lower limit of gas permeability is 5x10-17 me, and the lower limit of open porosity is 8.0 95.

I0OoZ2I

Preferably, the refractory material for the plate of the present invention has a coefficient of thermal expansion of 0.5 to 0.6 95, measured in a non-oxidizing atmosphere at 1000 "C.

The refractory material for the sliding nozzle plate must be heat-resistant because high-temperature molten steel passes through its inner hole. In particular, when the refractory material for the sliding nozzle plate is installed in the sliding nozzle device and is used under the conditions of restriction by means of a pushing metal member, etc., in order to reduce the thermal stresses generated during casting, it is important to reduce the coefficient of thermal expansion of the refractory material for the sliding nozzle nozzle plate. As a rule, the larger the shape of the plate, the greater the probability of failure due to thermal stress. However, from studies of the plate, which generally has the largest shape used so far, it was found that if the coefficient of thermal expansion at 1000 "C is about 0.695 or less, then significant destruction is avoided. On the other hand, if the amount of thermal expansion of the refractory material for the sliding of the nozzle plate during casting is too small, the restraining force of the metal strip in the outer circular direction of the plate decreases, and when it is less than the amount of thermal expansion of the metal strip, the restraining force disappears. Then there may be problems in the refractory material for the sliding nozzle plate, such as , cracks may occur, or cracks may spread, and when the plate is detached after casting, the metal strip is greatly displaced and the disassembly operation becomes difficult. For these reasons, the coefficient of thermal expansion at 1000 "C is preferably about 0.5 95 or more.

I0OZZI

Preferably, the refractory material for the plate of the present invention has a flexural strength of 15 to 40 MPa measured at room temperature. The refractory material for the sliding nozzle plate is installed in the sliding nozzle device, and is fixed by applying surface pressure in the thickness direction, and is also fixed by means of holding equipment, etc., on the periphery. When the mechanical strength of the refractory

Of the material for the sliding nozzle plate fixed in this way is low, the failure is caused by the restraining force. If the flexural strength of the refractory material for the plate of the present invention, measured at room temperature, is less than 15 MPa, the authors have found from experience that cracks may occur during installation or fixation in the sliding nozzle device, or when the pressure surface is loaded. Therefore, the flexural strength at room temperature is preferably 15 MPa or more. On the other hand, if the flexural strength at ordinary temperature increases, the modulus of elasticity also increases, which is a factor in the deterioration of heat resistance. If the flexural strength of the refractory material for the plate of the present invention, measured at room temperature, exceeds 45 MPa, the inventors have found from experience that the modulus of elasticity is likely to be excessively high and cracks may occur due to thermal shock. Therefore, the bending strength at room temperature is preferably from 15 to 40 MPa.

IOOZA

The method of obtaining the refractory material for the plate according to the present invention will be described below.

I0OZ5I

As a general rule, the refractory material for the sliding nozzle plate can be produced by a production method that includes the following steps. (A) The specified amount of raw materials of each component of the refractory material for the sliding nozzle plate are combined and mixed to obtain a mixture of raw materials. (B) A resin is added and mixed into the mixture of raw materials, which forms a carbon bond after heat treatment and can be used as a regulator of the wet state of the mixture during molding and further, if necessary, a solvent, etc., to obtain the mixture. (C) The mixture is subjected to molding under pressure by any method and at any pressure to obtain a molded product from the mixture. (6) The formed product is subjected to drying and heat treatment (firing) in a non-oxidizing atmosphere. (E) If necessary, perform polishing, winding of metal tape, etc.

I0OZ6)

In such a general method of obtaining a refractory material for a sliding nozzle plate, the method of obtaining a refractory material for a plate according to this invention is characterized by the fact that it includes the steps: setting the content of the metal AI component in the mixture in the amount of 2.0-10.0 wt. 95; formation of the mixture; and subjecting the mixture to heat treatment in a non-oxidizing atmosphere at 1000 "С or more to obtain a refractory material in which the content of the metal AI component is 1.0 wt. 96 or less (including zero).

I0OZ7I

If the content of the metal AI component in the mixture is less than 2.0 wt. 95, then a compacted structure cannot be obtained after heat treatment. In other words, if the product formed from a mixture containing a metal AI component in the amount of 2.0 wt. 95 or more, subjected to heat treatment at a temperature of 1000 "C or more in a non-oxidizing atmosphere, the metal AI component in the formed product reacts with other components to obtain reaction products such as

AIM, AI«Sz, AIg6 OS, AIgO4C, AIg2Oz, etc., causing compaction of the structure due to volume expansion of accompanying reaction products. The form of the metal AI as the source of the metal AI component (raw material) can be crushed grains, lamellar grains, fibers or the like. In addition to metal AI, alloy A1I-5i, AI-Ma, etc. can also be used.

I0OZ8)I

On the other hand, if the content of the metal AI component in the mixture exceeds 10.0 wt. 95, then the amount of the metal AI component in the refractory material (refractory material for the plate as a product) may exceed 1.0 wt. 95. But if the content of the metal AI component in the mixture is in the amount of 2.0 to 10.0 wt. 95, depending on the heat treatment conditions and the form of the metal AI or AI alloy, as a source of the metal AI component (raw material), etc., the metal AI component may not remain in the refractory material after heat treatment.

Including such cases, in this invention, the content of the metal AI component in the refractory material after heat treatment is set equal to 1.0 wt. 95 or less (including zero).

I0OZ9

The melting point of metallic AI is 660 "C. However, for example, in the case when

With the form of metallic AI, there are crushed grains in which the surface layer of the grains is covered with an oxide film, or fibers that have a relatively large shape, even if the temperature is not lower than the melting temperature of metallic AI, a large amount of metallic A! the component can remain at a temperature below 1000 C. Therefore, it is necessary to perform firing at a high temperature of 1000 "C or more in order to sufficiently react the metal Al of the component with the other components in order to seal the structure. 0040)

In addition, heat treatment must be performed in a non-oxidizing atmosphere. However, as heat treatment in a non-oxidizing atmosphere, in addition to nitrogen atmosphere, argon atmosphere and CO atmosphere, in which the heat treatment is carried out by embedding in coke, it is also possible to undergo heat treatment in a simple CO atmosphere, in which the molded product is placed inside a container made of metal, such as 5IS or 505, and is heated 3-outside the container by a torch or similar means. On the other hand, during heat treatment in an oxidizing atmosphere, for example, in the ambient atmosphere, not only is the carbon of the formed product oxidized, but also AIM, AiPgS3 are not formed,

AI2OS, AOS, etc., which makes it possible to compact the structure.

IO0ATI

In the present invention, in order to obtain a gas permeability of 40x1077 me or less, which is measured for a refractory material including a surface serving as a sliding surface and in a direction perpendicular to said surface, the composition of various raw materials, etc., as described above , in particular, the morphology and amount of metallic AI and the conditions of further heat treatment can be adjusted. In the conditions of heat treatment, calcination is performed in a non-oxidizing atmosphere at a temperature of 1000 "C or more (for example, a temperature of 1200 "C or more in a nitrogen atmosphere with an oxygen concentration of 100 ppm or less). The method of fine adjustment of oxygen concentration for each temperature region, partial pressures of nitrogen and CO, etc., is also effective.

In addition, in relation to each raw material, it is possible to apply the method of selection as dense as possible and forming with an oil press or a friction press at a pressure of 100 MPa or more, for example, using raw materials containing AI404C obtained by the method of arc melting.

In addition, the gas permeability can be adjusted to the above value by means of such methods as reducing the diameter of the fraction of small particles, adjusting the ratio of the structure of large, medium and small particles by size, increasing the pressure applied during molding, increasing the number of drafts, adjusting the speed at

B pressure, etc. so as to make the particle size composition of the mixture, especially the fine fraction, tend to form a densely packed structure.

Open porosity control is also similar to these techniques.

In addition, there are aspects that cannot accurately capture and express the density of the structure with only open porosity, and therefore it is necessary to estimate the density through a comprehensive evaluation with open porosity and gas permeability. 0042

A specific method in which the product is formed from a mixture selected in such a way that the content of the metal AI component is from 2.0 to 10.0 wt. 95, subjected to heat treatment to obtain a refractory material containing a metal AI component in the amount of 1.0 wt. Uo or less, includes optimal regulation of, for example, temperature, gas components, such as oxygen partial pressure, gas flow rate, etc., for each of the above methods.

I0043

As described above, it is common practice in the production of refractory material for the sliding nozzle plate to impregnate with tar, pitch or thermosetting resin in order to seal the structure etc. However, in the method for obtaining a refractory material for a plate according to the present invention, the stage of impregnation with a die, pitch or thermosetting resin is not necessarily required. 00441

Each of the tar, pitch or thermosetting resin ultimately leaves residual carbon.

Among them, thermosetting resin forms a solid rigid amorphous carbon structure and is effective in increasing strength. However, it will probably lead to a decrease in heat resistance. On the other hand, tar and pitch are solid at room temperature, soften at temperatures from several tens of "C to one hundred and several tens of "C, forming a liquid, and have

From a high rate of carbonization during heat treatment at high temperature and turn into crystalline carbon after heat treatment. Therefore, the impregnation of the refractory material for the sliding nozzle plate in a given temperature regime with tar or pitch has a sealing effect, which significantly reduces gas permeability and open porosity, and maintains density even after carbonization, which leads to the production of crystalline soft carbon. Thus, the increase in the modulus of elasticity is restrained, and the negative effect of the decrease in heat resistance is small. However, when impregnated with tar, pitch or thermosetting resin, the carbon will be present in such a way as to fill the voids in the refractory structure. Accordingly, the amount of free carbon component in the refractory material becomes high, and there is a large amount of carbon around the oxide raw material, such as A/I2Oz grains. As a result, the oxide material, such as AI2O3z particles, 2gO2 mullite, etc., will be restored in the so-called high efficiency during long-term casting. This makes it easier for the embrittlement layer to form due to the release or transformation of these oxide materials etc. near the working surface, which can further accelerate damage to the sliding surface. Therefore, according to the method of obtaining a refractory material for a plate according to the present invention, it is preferable not to impregnate with tar, pitch or thermosetting resin.

EXAMPLES

0045)

Table 1 presents Examples of the Invention and Comparative Examples. In Examples for

According to the invention and Comparative Examples in Table 1, the raw materials were weighed and mixed so as to have the corresponding given raw material compositions and the particle distribution was set, while an organic binder was added and mixed with the mixed raw materials to obtain a mixture that was uniaxially pressed into a lamellar body under the given forming conditions. The formed product was subjected to heat treatment at a given temperature and atmosphere to form a refractory material for the sliding nozzle plate. Volumetric specific gravity, open porosity, gas permeability, flexural strength, modulus of elasticity and coefficient of thermal expansion were evaluated, and for the evaluation of chemical components, the AI"04C" component, A/HgOz component, 5iO" component and free carbon were quantified. In addition, tests on the reaction with molten steel and tests on the reaction with molten cast iron were carried out using a high-frequency induction furnace to evaluate the formation of a brittle layer. In addition,

heat resistance was also evaluated using a high-frequency induction furnace. The methods of these assessments are as follows. 0046)

Bulk density and open porosity were measured according to 995 H2205. Samples for measuring bulk density and open porosity were cut into a shape of 40mmx4O0mmx4Ωmm, including the surface serving as the sliding surface of the refractory material for the sliding nozzle plate, and measured in the direction perpendicular to the surface serving as the sliding surface of the refractory material for the sliding nozzle plate. When the shape of the refractory material for the sliding nozzle plate is small, samples cut in a similar shape with dimensions of 30 mmx30 mxZOmm can be evaluated. 00471

Gas permeability was measured according to 5 82115 (2008). Samples for gas permeability measurement were taken to be 50 mm in size, including the sliding surface of the refractory material for the sliding nozzle plate, and cut into a shape with a thickness of 20 mm in the direction perpendicular to the sliding surface. In this sample, the surface serving as the sliding surface and the surface of the 20 mm thick side were parallel. The gas permeability of this sample was measured in the direction perpendicular to the surface that serves as the sliding surface. 0048)

The flexural strength was measured using a sample cut in the form of 20mmx20mmxvOmm according to 5-8 2213 (1995).

I0049)

The modulus of elasticity was measured by the ultrasonic method. In particular, the measuring ends were placed at both ends of the sample cut in the shape of 20mmx20mmxhOhm to measure the acoustic velocity, and the modulus of elasticity was calculated by calculating the ratio between the acoustic velocity and the bulk density measured according to U15-H2205.

I0O5O

The coefficient of thermal expansion was measured up to 1000 "C in a nitrogen atmosphere by the non-contact method described in 415-8 2207-1.

From 0051

Among the chemical components, the AI404C component, the A25Oz component, and the metallic AI component were quantified by the Rietveld method using X-ray diffraction. If a standard sample is available, quantification can also be performed using an internal standard method similar to X-ray diffraction. When analyzed by conventional X-ray fluorescent or wet methods, it is very difficult to separate and quantify AlO 4 C and Al 2 O 3 , and thus it is desirable to quantify X-ray diffraction. Similarly, in relation to the quantitative determination of the metallic AI component, when the AI-04C component is contained, it is practically impossible to separate and quantify AI404C by analysis using atomic absorption,

ISR, etc., wet method.

The 5iO2 component was determined quantitatively by the method of fluorescence diffraction of X-rays according to 45-28 2216.

The free carbon component (indicated as "V.V." in Table 1) was quantitatively determined by the method prescribed in LI5-B8 2011. (0Оо52И

The formation of a brittle layer was evaluated by means of a reaction test with molten steel and a reaction test with molten cast iron using a high frequency induction furnace as described above.

In particular, the surface serving as the sliding surface of the refractory material for the sliding nozzle plate was laid out in the high-frequency induction furnace to be the inner surface of the high-frequency induction furnace, and then the brittle layer formed by the reaction test with molten steel or molten steel was evaluated. cast iron

Regarding the evaluation method of the embrittlement layer on the sliding surface of the plate due to the oxygen in the molten steel (oxidation and decarburization are mainly caused by the molten steel), as the molten steel 55400 was used and the adjustment was made by adding b5i and carbon so that the concentration of free oxygen during the test was in the range from 30 to 50 ppt.

As for the method of evaluating the formation of a brittle layer, mainly due to the reduction reaction inside the refractory material, it was established that when using molten iron, which contains almost no oxygen and has a carbon content of about 4 wt. 95, the oxygen concentration at the time of assessment was stable at 5 ppm or less.

Reaction tests were carried out at 1600 C for 3 hours. After conducting reaction tests, the lining of the high-frequency induction furnace was broken and the thickness of the crumbled layer formed on the surface, which serves as the sliding surface of the refractory material for the sliding nozzle plate (the inner surface of the furnace of the high-frequency induction furnace), was measured. In Table 1, the thickness of the crushed layer is expressed as an index, where the thickness of the crushed layer in the example is 100. The smaller the index, the thinner the crushed layer, and the better the resistance of the surface to cracking. As described in

Non-Patent Document 2, the molten cast iron reaction test can well reproduce the sliding surface structure during the pouring operation of molten steel having a low concentration of free oxygen, such as AI deoxidized steel. (0053)

Thermal resistance was evaluated using the so-called immersion thermal shock test, in which the sample was immersed in molten iron in a high-frequency induction furnace and the degree of cracking of the sample after cooling was assessed. Specifically, a 40mmx40mmx180mm sample was cut from a refractory plate, and the test series was repeated three times, in which the sample was immersed in molten iron at 1600 "C for 3 minutes, and then cooled in air for 30 minutes. After the test, the degree of cracking of the sample was determined.

I0O541

In addition, some examples and comparative examples were applied in production conditions (working in real conditions). In production tests, by casting two types of molten steel, i.e. high-oxygen molten steel (steel having a concentration of free oxygen in the molten steel above 30 ppm) and low-oxygen molten steel (steel having a concentration of free oxygen in the molten steel of molten steel 30 ppt and less), the samples were evaluated according to the damaged condition of the refractory material for the sliding nozzle plate, etc., according to a total of three criteria o (Excellent), A (Good) and x (Unsatisfactory).

I0O55)

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I0O56)

In Table 1, in Examples 1-3, the content of the AI«O4C component is in the range from 15.0 to 45.0 wt. uyu, the content of the 5iO" component is within 2.0 wt. 95, the content of the free carbon component is within 3.0 mass: 95, and the content of the metal AI component is within 1.0 mass. Uo or less, each of which falls within the scope of the present invention, and properties such as open porosity, gas permeability, flexural strength, coefficient of thermal expansion also fall within the scope of the present invention. Therefore, as a result of the reaction test with molten steel and the reaction test with molten cast iron, the formation of a brittle layer was insignificant and the evaluation of heat resistance was good. As a result of testing the materials according to Examples 1-3 in production conditions, good durability was obtained.

On the other hand, in Comparative Example 1, the content of the A/«02:C component was only 13.0 wt. 6, and the effect of reducing the coefficient of thermal expansion was low. Thus, a large crack was formed as a result of the heat resistance assessment, and therefore good durability cannot be expected.

In Comparative Example 2, the content of the AI«02C component reached 48.0 wt. 905, and thus the coefficient of thermal expansion became extremely low. As a result, when the plate is detached from the sliding nozzle device after actual use, the heat-shrink tape (HB) on the outer periphery of the plate is displaced, and thus the disassembly property is poor. In addition, cracks developed that made reuse difficult, and as a result the plate was rated as unsatisfactory.

IOO57I

In Examples 4 and 5, the content of the free carbon component was 2.0 wt. 95, and 4.5 wt. 95, the content of the AIO4C component - 30.0 wt. 95, the content of the component 51iO»5 - 2.0 wt. 95, the content of the metal AI component was 1.0 wt. 95 or less, each of which falls within the scope of the present invention, and properties such as open porosity, gas permeability, flexural strength, coefficient of thermal expansion also fall within the scope of the present invention.

Therefore, as a result of the reaction test with molten steel and the reaction test with molten cast iron, the formation of a brittle layer was insignificant and the evaluation of heat resistance was good.

On the other hand, in Comparative Example C, the content of the free carbon component was only 1.0 wt. 95 and thus the modulus of elasticity becomes high. As a result, the Comparative

Example C was evaluated as the worst in terms of heat resistance. Thus, even in production conditions, it is not necessary to expect an acceptable durability.

Next, in Comparative Example 4, the content of the free carbon component reached 5.0 wt. oh, and thus in the molten steel reaction test and the molten cast iron reaction test, the formed brittle layer was thick. Thus, even in production conditions, it is not necessary to expect an acceptable durability.

I0O58)

In Examples 6 and 7, the content of the 5iO2 component was 0.5 wt 95 and 4.0 wt 95, respectively, the content of the AI404C component was 30.0 wt. 95, the content of the carbon component was 3.0 wt. hey and the content of the metal AI component was 1.0 wt. 95 or less, each of which falls within the scope of the present invention, and properties such as open porosity, gas permeability, flexural strength, coefficient of thermal expansion also fall within the scope of the present invention. Therefore, as a result of the reaction test with molten steel and the reaction test with molten cast iron, the formation of a brittle layer was insignificant and the evaluation of heat resistance was good.

On the other hand, Comparative Example 5 does not contain the component 5iO", and thus during processing and after processing for recovery and reuse after actual use, spalling occurred.

In addition, in Comparative Example 6, the content of the 51iO2 component reached 4.5 wt. 95, and thus the formation of a brittle layer was noticeable in the reaction test with molten cast iron.

I0O59)

In Examples 8 and 9, the content of the AI204C component was 30.0 wt. 95, the content of the component 51iO» 2.0 wt. 95, the content of the free carbon component is 3.0 wt., 9Uo, and the content of the metal AI component is 1.0 wt. 965 or less, each of which falls within the scope of the present invention, and properties such as open porosity, gas permeability, flexural strength, coefficient of thermal expansion also fall within the scope of the present invention. However, Examples 8 and 9 were carried out by high-pressure molding, and thus in Example 8, the open porosity was 7.8 95 , while in Example 9 the open porosity was 7.0 95 , and the gas permeability was up to 8x1077 me , and both examples have a high modulus of elasticity. Therefore, despite the fact that the formation of a brittle layer was quite insignificant in the reaction test with molten steel and the reaction test with molten cast iron, but still the heat resistance was slightly degraded. In addition, when tested under production conditions, although the damage on the sliding surface was insignificant, the radial crack on the side of the nozzle opening was slightly larger.

However, overall better results can be obtained than with a comparable conventional product.

I0ObO

In Example 10, the heat treatment temperature was 1000 °C, the content of the AOS component was 30.0 wt. 95, the content of the 5iO component was 2.0 wt. 95, the content of the free carbon component was 2.0 wt. U", and the content of metallic AI component was 1.0 wt.95 or less, each of which falls within the scope of the present invention, and properties such as open porosity, gas permeability, flexural strength, coefficient of thermal expansion also fall within the scope of the present invention. Therefore, as a result of the test on the reaction with molten steel and the test on the reaction with molten cast iron, the formation of a brittle layer was insignificant and the evaluation of heat resistance was good.

On the other hand, in Comparative Example 7, the annealing temperature is only 900 °C, and despite the high pressure forming, the reaction of metal A! during the heat treatment was small. In addition, the compaction was insufficient and the content of the metal AI component was more than 1 .0 wt. 95. Therefore, in the reaction test with molten steel and the reaction test with molten cast iron, the formation of a brittle layer was also notable, even when tested under production conditions, surface cracking occurred, and as a result, good durability could not be obtained. 00611

In Comparative Example 8, the molding pressure during the molding of the refractory material for the sliding nozzle plate was adjusted and the bulk density was set low. For this reason, in Comparative Example 8, the annealing temperature was 1200 "C, the content of the AI404C component was 30.0 wt. 956, the content of the 5iO2 component was 2.0 wt. vol., the content of the free carbon component was 2.0 wt. 95, the content of the metal The AI component was 1.0 wt 96 or less, each of which falls within the scope of the present invention. However, the open porosity is 12.195 and the gas permeability is 43x1077 me, and thus the sealing is insufficient. Also, the flexural strength is 14 MPa .Therefore, in the molten steel reaction test and the molten cast iron reaction test, the formation of a brittle layer was also notable, and even in the production test, good durability was not expected. In addition, due to the insufficient strength in the production test a kind of crack occurs, different from radial cracks, etc., which occurs as a result of normal thermal loads, and at the same time the durability deteriorates. 0О62

In Example 11, pitch impregnation is performed, which falls within the scope of the present invention. However, the content of the free carbon component becomes high, and the carbon component is homogeneously present in the refractory structure. Therefore, as a result of the reaction test with molten cast iron, a reduction reaction occurs in the refractory structure and the formed brittle layer tends to be somewhat thick. On the other hand, as a result of the reaction test with molten steel, the formation of a brittle layer was insignificant. When testing in

From the production conditions, after the high-oxygen molten steel pouring operation, the sliding surface damage was negligible, while after the low-oxygen molten steel pouring operation, the sliding surface damage tended to be slightly larger. However, overall better results can be obtained than with a comparable conventional product.

Claims (5)

FORMULA OF THE INVENTION 1. A sliding nozzle plate made of refractory material for use in steel casting, the refractory material containing an AOS component in an amount of 15 to 45 wt. 905, free 40 carbon component in the amount from 2.0 to 4.5 wt. 95, 5iOo-component in the amount from 0.5 to 4.0 wt. 96, metal AI component in the amount of 1.0 wt. 95 or less, or a refractory material free from the metallic AI component, the remainder comprising the A/29Oz component as a major component, the refractory material including a surface serving as a sliding surface, and having a gas permeability of 5x1077 to 40x10-77 me, which is measured for the specified 45 refractory material that includes the specified surface, and in a direction perpendicular to the specified surface, and an open porosity of 8.0 to 11.0 95. 2. The plate according to claim 1, in which the refractory material has a thermal expansion coefficient of 0.5 to 0.695 when measured in a non-oxidizing atmosphere at 1000 "C, and a bending strength of 15 to 40 MPa when measured at room temperature. 50 3. The plate of claim 1 or claim 2, wherein the steel has a free oxygen concentration of 30 ppm or less, as measured in the molten state of the steel during casting. 4. The method of obtaining a sliding plate according to any of claims 1-3, and the method includes the steps of: forming a mixture containing: metal AI or an AI-containing alloy, the component AiI«O04C, a free carbon component, a 5iOho-component and an A2Oz component , while the total amount of 55 metal AI-component in the specified mixture is from 2.0 to 10.0 wt. 95 relative to 100 wt. to the specified mixture; and subjecting the formed product to heat treatment in a non-oxidizing atmosphere at 1000 C or more to adjust the content of the components in the refractory material of the sliding nozzle plate so that the content of the Ai2:04C component is in the range of 15 to 45 wt. 95, the content of 60 free carbon components ranges from 2.0 to 4.5 wt. 95, content 5iOg2- component is in the range from 0.5 to 4.0 wt. 95, and the content of the metal AI component in the refractory material is from 1.0 wt. 95 or less or equal to zero. 5. The method according to claim 4, which is carried out without the stage of impregnating the refractory material with tar, pitch or thermosetting resin.