JPH0230364B2 - SEIKOYOSHINKUDATSUGASUSOCHINORAININGUKOZO - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a lining structure for a vacuum degassing apparatus for steel manufacturing for producing clean steel. BACKGROUND OF THE INVENTION The quality requirements for steel materials used in civil engineering, architecture, ships, machinery, chemical, electrical industries, etc. are becoming stricter. In the steel manufacturing industry, high-quality steel products are manufactured by desulfurizing hot metal using a pig iron mixer and removing impurities using a vacuum degassing device. However, (1) slag, (2) deoxidation products such as Al ₂ O ₃ , (3) reoxidation of molten steel,
(4) Oxide-based inclusions caused by damage to refractories deteriorate the quality of steel materials. In order to deal with these problems, (1) slag is removed by slag cut during converter tapping, (2) deoxidized products are floated and removed by blowing inert gas into molten steel or by using synthetic flux. 3) Preventing contact between the atmosphere and molten steel to prevent re-oxidation of the molten steel, and (4) Using highly corrosion-resistant refractories to suppress damage to refractories. These methods have been effective. Problems to be Solved by the Invention The inclusions generated by damage to the refractory have a size of several tens of microns to several hundreds of microns, and are the most difficult oxide inclusions to float and separate. In other words, oxide inclusions with a size of 10 μm or less do not significantly affect the homogeneity of the steel material, and those with a size of several hundred μm or more float to the surface due to the buoyancy of the molten steel, causing almost no problem. On the other hand, several tens of μ
Oxide-based inclusions of ~ several hundred microns are suspended in molten steel and tend to remain in the steel as they are, degrading the quality of the steel material. The size of the oxide-based inclusions caused by the refractory is thought to be due to the fact that the refractory used has crystal grains of 30μ or more. Among oxide inclusions caused by refractories, SiO ₂
Since system inclusions are soft and malleable, they pose relatively no problem. On the other hand, Al ₂ O ₃ based, MgO based, and spinel based inclusions are hard and have no malleability and cause defects such as wire breakage and surface flaws. In the steelmaking process after the converter, the ladle is made of SiO _{2
-Al2O3 -} based or _ZrSiO4- based refractories are mainly used, and MgO-based coating materials are mainly used for continuous cast tundishes. The lining of vacuum degassing equipment such as the RH and DH methods is made of mag-chlorite brick or alumina castable, and the hot repair material is magnesia-based spray material or alumina-based injection material. That is, the RH and DH methods are a means of improving the quality of steel materials, but because they use MgO, Al ₂ O ₃ , and spinel-based refractories, they also have the potential to contaminate molten steel. The present invention covers a refractory lining of a degasser with a covering material made of limestone or dolomite,
The aim is to produce cleaner steel. Means for Solving the Problems The present inventors applied a coating material made of limestone and/or dolostone and a binder onto the lining refractory of a degasser by spraying, pouring, press-fitting, patching, etc. coated with a method and used with or without preheating at a temperature of 1000°C or higher. CaO or MgO generated from this limestone or dolomite coating
is a fine crystal of 10 μ or less, and several tens of μ to several hundred μ
The generation of oxide-based inclusions can be prevented. Limestone and/or dolomite of the present invention and one or more inorganic compounds or inorganic salts of alkali metals or alkaline earth metals or halogenated compounds are mixed together.
A coating material made of a binder containing 0.1 to 20% by weight is used as a refractory lining for degassing equipment.
The surface of chlorine brick, alumina castable, etc. is coated with a thickness of 5 to 50 m/m by spraying, pouring, press-fitting, patching, etc. to remove MgO caused by mag/chlorine brick or alumina castable.
This is a method for suppressing the generation of Al ₂ O ₃ and spinel-based oxide inclusions of several tens to hundreds of microns. If an inorganic compound or inorganic salt of an alkali metal or alkaline earth metal or a halogenated compound is used as a binder for limestone or dolomite, it will not shrink even when used at high temperatures and sintering will be prevented. Therefore, CaO or
MgO has a fine crystal diameter of 10μ or less and is active. The limestone and dolomite used in the present invention are not particularly limited, and may be those commonly used in Japan. In addition, in terms of particle size, there is no problem with the particle size normally used for refractories. The binder must be one or more inorganic compounds or salts of alkali metals or halogenated compounds. If inorganic compounds other than these are used, firing shrinkage is large and cracking and falling off are likely to occur, and crystal growth of CaO and MgO occurs, resulting in a crystal diameter of 10 μm or more, which is not preferable. That is,
When inorganic compounds, inorganic salts, or halogenated compounds of alkali metals or alkaline earth metals are used as a binder, the firing shrinkage is about 0 to 2% and it can be used as a structure, whereas when other binders are used Because it shows a shrinkage of 10% or more, it is prone to cracking and falling off, making it impossible to use it as a covering material. The amount of the binder added is within the range of 0.1 to 20% by weight, and if it is less than 0.1% by weight, the binding strength will be insufficient, and if it exceeds 20% by weight, the corrosion resistance will decrease, which is not preferable. Binders used include alkali phosphates such as sodium hexametaphosphate and potassium phosphate;
Alkali silicates such as No. 3 sodium silicate and potassium silicate, and halogenated compounds such as magnesium chloride, calcium chloride, and sodium chloride can be used. This coating material made from limestone or dolomite is sprayed, poured, press-fitted, patched, etc. onto the cold or hot surface of the lining refractory of vacuum degassing equipment such as RH and DH methods. Construct with a thickness of 50mm. If it is less than 5 mm, the durability of the coating layer will be poor and the working surface of the mag/chlorite brick or alumina caster will be exposed during the use of one charge, which is undesirable. If it exceeds 50 mm, the coating will take too long and the degassing snorkel This is not preferable because it reduces the internal volume of the container. Covering material made of limestone or dolomite is heated to 1000℃
In order to dissociate CO ₂ gas below, it is desirable to preheat to 1000°C or higher before use. Examples will be described below. Table 1 shows the quality and construction examples of limestone or dolomite covering materials. These coatings were applied to the snorkel part of a RH vacuum degasser. The coating method used was spraying and/or press fitting. A dry spraying method was used for spraying, and an automatic sprayer was used to spray the inside and outside of the snorkel after each charge. Press-fitting is suitable for large-volume, thick construction, and was applied to the inner surface of the snorkel. A comparison of the inclusion index in the ladle after degassing with and without a limestone or dolomite coating is shown in Table 2. From this result, inclusions in steel were reduced by using limestone or dolomite coating material, and the effect was recognized.

【table】

[Table] Effects of the Invention The present invention provides the following effects. (1) The crystal size of CaO or MgO produced from limestone or dolomite is less than 10μ and is unlikely to cause defects in steel materials. (2) Al ₂ O ₃ , a deoxidation product, can be absorbed by active CaO. (3) Active CaO can absorb S and P in steel.

Claims (1)

[Claims] 1 Limestone and/or dolomite and one or more inorganic compounds or inorganic salts of alkali metals or alkaline earth metals or halogenated compounds in an amount of 0.1
A lining structure for a vacuum degassing device for steel manufacturing, in which the surface of the inner lining refractory of the vacuum degassing device is coated with a coating material made of a binder containing ~20% by weight.