JPH032825B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a basic monolithic refractory that is useful as a lining refractory for molten metal containers, mainly for steel manufacturing, such as ladles, external refining furnaces, tundishes, etc. (hereinafter simply referred to as ladles, etc.). In recent years, in steel manufacturing, the tapping temperature has increased due to the adoption of continuous casting, degassing treatment, ladle refining, etc. to meet the increasing demand for high-grade steel, and the working temperature of ladle etc. has become higher. The conditions for using ladles, etc. are becoming increasingly severe, such as longer residence times. For this reason, high-grade refractories such as zircon or high alumina are now being used in place of the high silicic acid refractories that have been widely used as refractories for lining ladles, etc. At present, a sufficiently satisfactory service life in terms of slag corrosion resistance has not been achieved. Along with the dramatic increase in service life due to this improvement in slag corrosion resistance, attempts have been made to apply basic refractories to ladles, etc. for the purpose of purifying steel. Also, due to the occurrence of cracks due to structural spalling, the intrusion of metal into the cracks, and the wear and tear caused by the peeling of the refractory, the excellent effects of basic refractories cannot be utilized, and they are still not put into practical use. We haven't reached that point yet. In the construction of ladles, etc., there has been a shift from bricklaying construction to irregular-shaped construction using methods such as pouring and vibration molding. This irregular-shaped construction is easier than (1) brickwork construction. (2) There is no dust generation at the construction site, and the working environment is improved. (3) Refills can be made during intermediate repairs, and costs are reduced because there is no need to dispose of unused parts with remaining dimensions as in the case of bricks. (4) No need for firing during the manufacture of refractories, resulting in energy savings. There are many advantages such as, but the biggest advantage is labor saving by shortening the construction time. For example, in the case of constructing a 150-ton ladle, conventional brickwork would take three days, but pouring could be completed in just half a day. Therefore, it is thought that it would be optimal if the above-mentioned basic monolithic refractories were used for construction in a monolithic form, but molten metal containers such as ladles made of basic monolithic refractories have lower strength than those constructed using brickwork. It has the disadvantage of large volumetric change, poor filling, large thermal expansion characteristic of basic materials, and easy absorption of molten slag, resulting in concentrated cracking and peeling. Various attempts have been made to solve these problems. For example, (1) reduce the amount of added water. (2) Use a vibrator during pouring work. (3) Dry construction. Studies have been carried out, and although some improvement has been achieved through these measures, it is still insufficient. As a result of a detailed study on the occurrence of cracks in a basic monolithic refractory construction body due to heating and cooling, the present inventors found that the thermal stress generated within the construction body during heating and cooling particularly affects the matrix part. It spreads and concentrates on particularly weak points in the organization, creating large cracks. However, if coarse grains are present in the construction object, the stress propagation stops because the structure of the coarse grain portion is stronger than that of the matrix portion in the irregularly shaped construction object. However, if the coarse grains are not very large, when the stress propagates to the boundary with the coarse grains, it propagates around the coarse grains. If the grain size of these coarse grains is larger than a certain level, the propagation of stress will not be able to go around the coarse grains, and the propagation will stop there, and eventually the stress will not be concentrated at one point but will remain in a dispersed state. . Therefore, it was found that even though very fine cracks may occur in the matrix, they do not concentrate and become large cracks, and do not lead to the intrusion of metal or the occurrence of peeling. In other words, the coarse grains play a wedge-like role. As a result of various experiments, they found that the minimum particle size of coarse particles that can stop the concentration of cracks was 50 mm, and they filed a patent application (Japanese Patent Application No. 135389/1989). In other words, if coarse particles with a particle size of 50 mm or more are used, it can be applied to basic monolithic refractories such as ladles. However, if a basic amorphous material containing coarse grains with a grain size of 50 mm or more is used in a molten metal container such as a super-large ladle of 300 tons, cracks may occur in a part of the steel bath, causing the ground to deteriorate. There was an intrusion of money. Regarding the occurrence of this crack and the intrusion of metal,
A more detailed examination revealed that the microscopic cracks that had occurred in the matrix had become larger, allowing metal to penetrate. This crack is also caused by thermal stress generated within the construction body. Under restraint, the thermal stress generated within the construction object increases as the coefficient of thermal expansion of the refractory material increases, and also increases as the construction object becomes larger. If the construction object is not very large, the generated thermal stress will be absorbed by plastic deformation of the matrix portion, which has a relatively loose structure, as described above. Although thermal stress is also generated in the coarse grain portion, the coarse grain portion has greater strength than the matrix portion, and plastic deformation due to stress is less likely to occur, and the stress in the coarse grain portion is also absorbed by the matrix portion. The stress absorbed in this matrix portion remains as fine cracks, which are also separated by coarse grains. As the construction size increases, the thermal stress generated by basic materials, especially magnesia, which has a high coefficient of thermal expansion, increases, and the stress cannot be fully absorbed in the matrix, causing cracks to remain in a fine state and allowing the base metal to penetrate. It turned out that the crack was large enough to cause damage. As a result of further investigation, the inventors of the present invention found that the main cause of this cracking was thermal stress in the coarse grained part, and as a solution to this problem, the coarse grained part was made of a material with a smaller coefficient of thermal expansion than that of the matrix part. It was discovered that the use of That is, this invention is a basic monolithic refractory material with coarse grains manufactured using a material with a smaller coefficient of thermal expansion than that of the matrix part, which allows for the formation of coarse grains in the part of the construction body. Thermal stress is reduced, and the stress is sufficiently absorbed by the plastic deformation of the matrix. At the same time, due to the effect of the coarse grains, there are no concentrated cracks, which prevents the penetration of metal and the occurrence of peeling. It doesn't connect. When the basic monolithic refractory material of this invention was actually used in a super large ladle (300 tons), there were no continuous concentrated cracks, and therefore no metal intrusion or peeling occurred. When the same refractory material as the matrix was used for the coarse grains, cracks were concentrated in some areas and penetration of metal was observed, although not as much as when no coarse grains were used. The basic amorphous refractory material of the present invention contains 15 to 60% by weight of coarse particles with a particle size of 50 to 90 mm made of a material with a smaller coefficient of thermal expansion than basic refractories other than the coarse particles. and the particle size of coarse particles is 50
~90mm is appropriate; if it is less than 50mm, the propagation of the generated thermal stress cannot be stopped by the coarse grains, and cracks will concentrate, and if the grain size is more than 90mm, fluidity will decrease during kneading or construction, and grain separation will occur. Cheap. In addition, the mixing ratio of coarse particles is preferably 15 to 60% by weight; if it is less than 15% by weight, the number of coarse particles in the construction body is too small, cracks are not divided sufficiently, concentrated cracks occur, and metal intrusion occurs. , peeling occurs. Moreover, if it exceeds 60% by weight, the fluidity during kneading and construction will decrease, which is not preferable. The basic refractory material used for the coarse grains of this invention is one that does not react with components other than the coarse grains to form a low melting point substance or reduce slag corrosion resistance, and the smaller the coefficient of thermal expansion, the more preferable it is. is, than the coefficient of thermal expansion of basic refractory materials other than coarse grains.
It needs to be smaller than 10%. Suitable examples of such basic refractory materials include magnesia-alumina, chromite, chromium-magnesia, and magnesia-silica. On the other hand, the total content of MgO and CaO in the basic refractory material other than coarse particles is preferably 50% by weight or more. This is because if the total amount is less than 50% by weight, the basic refractory material loses its corrosion resistance against slag significantly. Components other than MgO and CaO include SiO ₂ ,
Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Cr ₂ O ₃ and the like,
It does not need to react with MgO or CaO to lower the melting point or significantly deteriorate other properties.
Examples of such basic refractory materials include seawater magnesia clinker, natural magnesia clinker, and stabilized dolomite clinker. Some materials used as coarse grains have slightly inferior slag corrosion resistance compared to materials used for the matrix portion, but there is no need to worry because the coarse grains themselves have greater slag corrosion resistance than the matrix portion. The coarse grains used in this invention need to have a compressive strength of 300 Kg/cm ² or more, preferably 500 Kg/cm ² or more, and an apparent porosity of 20% or less. This is because if the compressive strength is less than 300 kg/cm ² , thermal stress may cause cracks in the coarse grains themselves, or cracks occurring in the matrix may not be stopped, and the apparent porosity may be less than 20%. This is because if it exceeds the limit, slag will easily penetrate into the coarse particles, which is undesirable. Next, methods for producing the coarse particles used in this invention include a method in which raw materials are blended in particle size using a known brick manufacturing method, a binder is added, kneaded, molded, and fired, which is then coarsely crushed and sieved, a pelleter, a rolling mill, etc. Various methods are used, such as granulating it with a granulator or other method and using it as it is, or using natural chromite ore as it is or after calcination, coarsely crushing it and sieving it, and satisfying the conditions such as the physical properties mentioned above. There is no particular limitation as long as it is suitable. In addition to the coarse particles of the basic monolithic refractory according to the present invention, what particularly affects the construction method, properties, etc. is the fine powder portion (particle size of 0.125 mm or less). The refractory material used for this fine powder part is as described above, but when water is used for kneading, it is preferable to use one with as little free CaO as possible. The amount of fine powder used is adjusted by the amount of coarse particles used, but 25% of the refractory material
It is preferably 35% by weight. In addition to fire-resistant materials, binders, water-reducing agents, dispersants, peptizers, anti-explosion agents, thickeners, and other materials normally used for monolithic refractories may be used as appropriate; as binders, Self-hardening or thermosetting materials include aluminum phosphate, alumina cement, sodium silicate, magnesia cement, aluminum sulfate, clay, ethyl silicate, and the like. As water reducing agents, dispersants, and deflocculants, phosphates,
Silicates, sulfonic acid compounds, etc. are used, and various surfactants are used as explosion inhibitors. If appropriate amounts of these substances are used, the viscosity of the bond part will be relatively high in case of pouring construction, and particle separation due to sedimentation will be difficult to occur even if coarse particles are used. Known pulp waste liquid, silica gel, clay,
By adding a small amount of CMC, sodium alginate, PVA, etc., sedimentation of coarse particles can be prevented. As a method of constructing basic monolithic refractories using coarse particles according to the present invention into ladles, etc., known construction methods such as pouring, stamping, and vibration molding may be employed, but among these, the pouring method is the most suitable. preferable. In the case of this pouring construction, coarse particles and other refractory materials, additives such as binders are weighed, mixed using a mixer that does not involve compression as much as possible, such as a vortex mixer, mortar mixer, or cement mixer. Then add water to 5-8% of the solids.
Add and knead for 3 to 20 minutes, then pour into the mold. The curing time until demolding depends on the temperature, but it is 0.5 to 4
About an hour is preferable. It is then dried at elevated temperatures and used. The basic monolithic refractory using coarse particles made of a material with a low coefficient of thermal expansion according to the present invention is used as a refractory lining material for ladles, etc. used at high temperatures. The accompanying penetration and peeling of metal is prevented by using coarse grains with a grain size of 50 to 90 mm. In particular, by using coarse grains with a grain size of 50 to 90 mm, the cracks that occur intensively within 30 to 50 mm from the operating surface, which are found in basic irregularly shaped materials with a commonly used grain size structure, are separated and continuous. It does not become a crack. Furthermore, by using a refractory material with a low coefficient of thermal expansion for coarse grains, it is possible to prevent cracks from forming and intrusion of bare metal even in large construction objects such as ultra-large ladles, which has the characteristics of slag corrosion resistance of basic materials. This is to make full use of the At the same time, by using coarse particles with a small coefficient of thermal expansion,
By combining the thermal volume stability of the refractory layer, the wear resistance of molten steel, and the strength of the aggregate effect, the advantages of basic materials and amorphous materials can be fully utilized. The present invention will be explained in detail below with reference to Examples. Example 1 (Manufacture of coarse grains) (1) Blend fused spinel in particle size, add 30% bittern aqueous solution to 3% by weight of the refractory material, knead in a wet pan, mold into a regular brick shape with a 450 ton press, and then press into a tunnel. It was fired at 1580℃ in a kiln. The obtained fired bricks were crushed using a geocrusher and sieved to a size of 90 to 50 mm. The chemical composition and physical properties of the coarse particles produced are shown in Table 1.
Shown in No.1. (2) Coarse grains were produced in the same manner as in (1) using a refractory material consisting of 35% by weight of chromite and 65% by weight of seawater magnesia clinker. Its chemical composition and physical properties are shown in No. 2 of Table 1. (3) Natural chromium iron ore in a tunnel kiln at 1420℃
After firing, it was coarsely crushed using a geocrusher and sieved to a size of 90 to 50 mm. The chemical composition and physical properties of the coarse particles produced are shown in Table 1.
Shown in No.3. (4) In order to improve sinterability, coarse grains were produced in the same manner as in (1) using CaO-enriched seawater magnesia clinker. Its chemical composition and physical properties are shown in No. 4 of Table 1.

[Table] Examples 2 to 6 Insulating bricks with a thickness of 114 mm were built inside an iron container with a diameter of 3 m and a height of 1.5 m, which was assumed to be a ladle, and an iron core was placed in the center so that the layer thickness was 200 mm. was installed. The mixture of coarse particles and refractory material shown in Table 2 and the binder were mixed with a vortex mixer, water was added, and after kneading for 3 minutes, the mixture was poured into the container. Note that seawater magnesia clinker having the chemical composition shown in Table 3 was used as the refractory material other than the coarse particles. After leaving it for 2 hours, remove the core and immediately heat it to 1000℃ using an oxygen-propane burner at a heating rate of 100℃/hr.
The temperature was raised to °C, maintained for 3 hours, and then allowed to cool. After cooling,
The state of cracks on the surface was observed. Thereafter, the temperature was raised again to 1600°C at a heating rate of 100°C/hr and held for 10 hours. After that, in the heat,
Ladle slag having the chemical composition shown in Table 3 was sprayed. This spraying cooled the furnace to about 1000°C, so the temperature was raised again to 1600°C at a rate of 100°C/hr. This slag spraying-temperature raising operation was repeated five times and then allowed to cool. After cooling, the construction body was observed for cracks and peeling. The results are shown in Table 2. Table 2 also shows the results of Comparative Examples 1 to 4, which were conducted in exactly the same manner as Examples 2 to 6, except that the composition of coarse particles was different. In addition, Comparative Example 1 uses coarse grains (No. 4 in Table 1) that are outside the scope of the claims of this invention in terms of thermal expansion coefficient, and Comparative Examples 2 and 3 use coarse grains in an amount that is outside the claimed range of this invention. Comparative Example 4, which is outside the scope of the claims, does not use coarse particles defined in the present invention.

【table】

【table】

[Table] As is clear from the results in Table 2 above, coarse particles with a particle size of 50 to 90 mm made of a material with a small coefficient of thermal expansion are
The pouring material containing 15 to 60% by weight showed no cracking after heating and cooling at 1000°C. Furthermore, even after heating and cooling at 1600°C, there were no concentrated cracks, the crack width was as small as 1 mm or less, and no peeling was observed. However, those that do not use coarse particles, those that use coarse particles with a high coefficient of thermal expansion, or those that use a small amount of coarse particles with a low coefficient of thermal expansion,
Cracks occurred after heating to 1000°C, and after heating and cooling to 1600°C, both the length and width of the cracks increased, and some were accompanied by peeling. This confirmed the superiority of the refractory of this invention. Example 7 As a result of pouring the pouring material with the composition of Example 3 into a 300 ton ladle to a thickness of 180 mm, there were no concentrated cracks, no intrusion of base metal into the material, and no peeling, compared to Comparative Example 1. The durability was 1.3 times longer than when constructed with other materials.

Claims (1)

[Claims] 1. 15 to 60% by weight of coarse particles with a particle size of 50 to 90 mm in the basic refractory material whose coefficient of thermal expansion is smaller than that of the basic refractory material other than the coarse particles.
A basic monolithic refractory for use in molten metal containers, characterized in that it is formulated with: