JPH0247926B2 - YOKOKAIZAIBUTSUJOKYOYOSETSUKAISHITSUFUIRUTAANOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a filter for removing inclusions such as SiO ₂ and Al ₂ O ₃ , as well as sulfur and phosphorus contained in molten steel. BACKGROUND OF THE INVENTION In recent years, steel used for marine structures, chemical industry containers, sour gas resistant pipes, etc. is required to have a cleaner quality. For this reason, pre-treatment and post-treatment of hot metal, degassing of molten steel, and desulfurization by Ca-Si injection have started to be carried out, and the quality of steel has improved markedly. Further improvements in the quality of steel are required in applications with severe conditions. Therefore, various studies are being conducted to reduce inclusions in the tandate, which is the final process of steelmaking.
That is, attempts have been made to reduce inclusions in steel by changing the shape of the tundish, the structure of the filter, appropriate lining, etc. Particularly recently, calcareous linings are being considered because they allow easy removal of inclusions in steel. In other words, Japanese Utility Model Application No. 57-76956 describes tandem refractories made of calcareous refractories with CaO of 90% or more, or "Tetsu to Hagane" published by the Iron and Steel Institute of Japan, 1983, Vol. 69, No. 12.
The development of the technology for applying CaO refractories to tundishes, or the patent application published by some of the inventors in the No.
Publication No. 55-51763 reports the use of limestone refractories for coating materials and other tundishes using limestone. However, with the lining material of the tandate, it is difficult to expect much contact reaction with molten steel, and for this reason, the following calcareous filters are being considered. That is, JP-A-58-193306 discloses a lime clinker alone or a calcareous filter with a large number of molten steel passage holes made by adding dolomite or magnesia clinker to lime clinker of 50% by weight or more, or JP-A-59-156556 The method used is to stack lime-based cylindrical refractories as filters. However, the following problems can be raised. First, lime clinker is used, but this is dead burnt lime, which is very dense and has poor reactivity, so it has a low ability to absorb inclusions. Secondly, a large number of molten steel ventilation holes are provided, but since they are all straight holes, they have a disadvantage of low porosity and low contact reaction with molten steel.
It is still insufficient to sufficiently absorb inclusions of molten steel. Furthermore, on page 102 of ``Development and Application of Porous Ceramics'' (published on February 27, 1984) edited by Makoto Hattori and Shoji Yamanaka, there is a description of the transfer of molten metal by a ceramic foam with an alumina-cordierite network structure. However, this method only physically removes inclusions and does not have the ability to chemically absorb and remove inclusions such as Al ₂ O ₃ and SiO ₂ , as well as sulfur and phosphorus. It can be said that the ability to remove inclusions, etc. is still insufficient. In addition, pressure resistance or bending strength is low, and structural strength against molten steel is insufficient. Problems to be Solved by the Invention The present invention is a lime filter having a network structure made of limestone or dolomite, and since this filter is composed of active CaO, Easily reacts with inclusions.
Therefore, inclusions in steel can be reduced very efficiently from the structural and material standpoints. The present inventors have discovered that inclusions such as Al ₂ O ₃ and SiO ₂ in molten steel, as well as sulfur and phosphorus, can be removed by using a lime filter with a porous structure made from limestone or dolomite. It was discovered that it can be removed efficiently. That is, by passing the molten steel through the porous lime porous body, contact between the lime and the molten steel is very good, and therefore inclusions in the steel can be efficiently removed. The present invention uses one or two types of limestone or dolostone.
100 parts by weight of seeds and 0.1 to 100 parts of an alkali metal inorganic compound or one or more halogen compounds.
20 parts by weight of refractory is made into a slurry and poured into the void of an organic aggregate made of organic resin such as foamed urethane beads, foamed polystyrene beads, polyethylene beads, etc., where the surfaces are in contact with each other, and then dried.
It is fired at 1000℃ or higher to remove organic resin and dissociate CO ₂ from limestone and dolomite, creating a CaO filter. The limestone and dolomite used in the present invention are not particularly limited, and any commercially available ones may be used. The particle size is preferably 0.3 mm or less, preferably 0.074 mm or less. As a binder, a halogen compound such as salt, calcium chloride, magnesium chloride or/and sodium hexametaphosphate, monopotassium phosphate, 3
0.1 to 20% of alkali metal inorganic compounds such as sodium silicate, lithium silicate, borax, and sodium aluminate.
When added in parts by weight, the firing shrinkage of limestone is suppressed to about 0 to 2%, and an active CaO molded body can be obtained. Water is added to the calcareous refractory having such a structure to form a slurry, which is then poured into the void of the organic aggregate made by the method described below. That is, the organic aggregate is made of organic resin such as foamed urethane beads, foamed styrene beads, polyethylene beads, etc., and it is important that the spherical surfaces of the organic beads are in contact with each other. This contact is not a point contact, but is 1/2 to 1/2 of the maximum cross-sectional area of the organic beads used.
Preferably, it is a surface contact having a contact area of 1/20. When it exceeds 1/2, the strength of the porous body decreases, and when it is less than 1/20, sufficient molten steel permeability cannot be obtained. The organic beads are made into an organic aggregate using an adhesive.
The diameter of the organic beads is preferably 0.1 to 80 mm. When the surface contact portions of the organic beads disappear by firing, they become openings. If the opening is less than 0.1 mm, the permeability of molten steel will be greatly reduced, which is not preferable. Moreover, if it exceeds 80 mm, the degree of contact with molten steel will decrease, which is not preferable. This limits the diameter of the organic beads. The viscosity of the calcareous refractory slurry is preferably in the range of 10 to 500 poise.If it exceeds 500 poise, it is difficult to soak the slurry, and if it is less than 10 poise, solid-liquid separation of the solution and powder will occur, so it is preferable. do not have.
The ratio of calcareous refractory to water should be in the range of 9:1 to 1:10. After pouring the calcareous refractory, it is dried and fired at a temperature of 1000℃ or higher. That is, it is necessary to eliminate the aforementioned organic aggregates and dissociate carbon dioxide gas from limestone or dolomite to form porous and active CaO. It was made like this
The CaO skeleton has many fine pores of 10μ or less, and the crystal size is small, 10μ or less. For this reason, it is characterized by an extremely excellent ability to chemically adsorb inclusions, and in combination with the ability to physically remove inclusions due to its porous structure, an excellent filter effect can be obtained. The pores of the calcareous filter made in this way are continuous, and the porosity is 50 to 90%. As the molten steel passes through these continuous porous pores, the contact reaction between the molten steel and CaO becomes extremely large, making it possible to physically remove non-metallic inclusions such as SiO ₂ and Al ₂ O ₃ in the steel. chemically active
CaO can absorb nonmetallic inclusions such as SiO ₂ and Al ₂ O ₃ or sulfur and phosphorus. This filter is not only used to remove inclusions such as SiO ₂ and Al ₂ O ₃ , sulfur, and phosphorus in molten steel, but also to remove sulfur and phosphorus in hot metal, and to remove impurities in nonferrous metals. It can also be used for Example The quality of the filter of the present invention is shown in Table 1. After applying a self-hardening epoxy resin to the surface of the various organic beads shown in Table 1, press molding is performed to reduce the contact area of the beads to 1/2 to 1/1 of the maximum cross-sectional area of the bead diameter.
An organic aggregate adjusted to 0 was formed. After the organic aggregate was completely hardened, a slurry of limestone or limestone and dolomite was poured into the slurry by vibration, dried, and fired at 1500°C for 2 hours. As a result, three types of products of the present invention shown in Table 1 were obtained, and the removal of nonmetallic inclusions and SP from steel was investigated through an actual furnace test in a 35-ton tundish of Company A.

[Table] 〓 Skeletal specific gravity 〓
*2: Shown as a percentage when the comparative product is set as 1.
For comparison, a conventional weir made of lime bricks was used. This weir is 500mm x 500mm x 50mm, and
It has 256 20φ molten steel passage holes. The porosity is
As low as 32%. In contrast, the shape of the product of the present invention is 500
The shape was the same as mm x 500 mm x 50 mm. Effects of the Invention The calcareous filter manufactured by the method of the present invention has excellent porosity and can absorb non-metallic inclusions such as SiO ₂ and Al ₂ O ₃ in molten steel, as well as sulfur and phosphorus, etc. very efficiently. The effect of facilitating the production of the desired ultra-clean steel could be achieved.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the organic beads of the present invention impregnated with slurry, and Figure 2 is a sectional view showing the structure of a calcareous filter with pores after the organic resin has been removed by firing. Yes, In the figure, 1... calcareous refractory slurry, 2... organic beads, 3... calcareous refractory, 4... pores.

Claims (1)

[Claims] 1 100 parts by weight of one or two types of limestone and dolomite, salt, halogen compounds such as calcium chloride, magnesium chloride, and/or sodium hexametaphosphate, monopotassium phosphate, No. 3 sodium silicate, lithium silicate, borax, 0.1 to 20% of one or more alkali metal inorganic compounds such as sodium aluminate
A calcareous filter for removing inclusions from molten steel is produced by pouring a refractory slurry containing parts by weight into the voids of an organic resin aggregate whose spherical surfaces are in contact with each other, drying and solidifying it, and then firing it at a temperature of 1000°C or higher. Production method.