JPH0251869B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a converter, an electric furnace, an AOD furnace, a VOD pot,
This invention relates to a basic refractory composition for flame spraying (hereinafter simply referred to as thermal spray material) used for flame spray repair of steelmaking furnaces such as RH. In recent years, flame spray repair has begun to be widely considered as an alternative to conventional wet repair, and
Flame spraying is beginning to be put into practical use in steelmaking furnaces such as . These flame spraying methods include a gaseous fuel-oxygen method, a liquid fuel-oxygen method, and a solid fuel-oxygen method. For gas or liquid fuel-oxygen flame spraying, spray materials such as magnesia-alumina, dolomite-alumina, and magnesia-LD slag are used. Thermal spray materials such as coke-magnesia are used in solid fuel-oxygen flame spraying. It is difficult to melt basic materials with high melting points such as magnesia, dolomite, and lime with these thermal spraying methods, so various low melting point materials such as the above-mentioned alumina, LD slag, and coke ash are added to increase the melting point. Makes it easier to bond basic materials. Although the addition of various low melting point substances improves adhesion, it reduces the corrosion resistance or strength of the thermally sprayed layer (hereinafter simply referred to as the thermally sprayed layer), so it must be used with sufficient selection. For example, the disadvantages of magnesia-alumina or dolomite-alumina thermal sprayed materials are converters,
When used at high temperatures in an oxygen blowing vessel such as an AOD furnace and under operating conditions where the slag basicity is 1 or more, the corrosion resistance of the sprayed layer is poor and its durability is insufficient. Furthermore, although magnesia-LD slag-based thermal spray materials have high corrosion resistance against the slag of the oxygen blowing vessels of converters and AOD furnaces, they have low hot strength and have the drawback of not being able to sufficiently withstand wear of molten steel. The sprayed layer of the magnesia-coke-based thermal sprayed material is very porous, and the ash content of the coke has low basicity, which lowers the refractoriness of the sprayed layer, resulting in poor corrosion resistance. The present invention was made in order to eliminate the drawbacks of the above-mentioned thermal sprayed materials, and provides a high adhesion rate, high hot bonding strength and hot bending strength, and high hot volume stability and corrosion resistance. This provides a thermal spray material with excellent properties. That is, the present invention uses one or more basic aggregates of magnesia, dolomite, and lime in an amount of 50 to 95
The present invention relates to a basic refractory composition for flame spraying, which comprises 5 to 50 parts by weight of Portland cement and is used for flame spray repair of steelmaking furnaces. The thermal spraying material of the present invention contains 50 to 95 parts by weight of one or more of magnesia clinker, dolomite clinker, or lime clinker whose particle size is adjusted to 1 mm or less, and 5 parts by weight of Portland cement whose particle size is also adjusted to 1 mm or less. It is a basic material for flame spraying consisting of ~50 parts by weight. Magnesia clinker, dolomite clinker, and lime clinker are not particularly limited.
It may be natural or synthetically produced. The particle size is preferably 1 mm or less and dried. When the grain size is 1 mm or more, there is a disadvantage that rebound loss is large and the construction yield is reduced. Preferably, the content of fine powder of 10μ or less is 20%; if it exceeds 20%, the conveyance of the material will decrease and the material will be discharged unevenly during thermal spraying, and the thermal sprayed layer will become a dense layer.
It becomes a porous layer and becomes easy to peel off. Portland cement added as a low-melting point material to strengthen adhesive strength is not particularly limited, and any commercially available cement may be used. The CaO/SiO ₂ molar ratio of Portland cement is usually about 3, and the main mineral composition is tricalcium silicate, which has a high melting point, so the CaO/SiO ₂ molar ratio of the connective tissue of the sprayed layer can be increased. Therefore, it has high hot strength and high resistance to slag with a basicity of 1 or more generated in steelmaking furnaces. The chemical composition of this Portland cement is CaO60
% or more, SiO ₂ is 25% or less, and other components are preferably 15% or less. Most of Portland cement has a particle size of 10μ or less, and depending on the particle size of magnesia, dolomite, and lime clinker, it can be used as is, but it can be adjusted to a particle size suitable for thermal spraying using a known granulation method. It is desirable to use the The particle size of Portland cement is preferably 1000 to 10μ in terms of transportability and meltability. If the particle size is 1000μ or more, the meltability is poor, and if the number of particles smaller than 10μ increases, the transportability will deteriorate. Therefore, particles smaller than 10μ account for 20%
The following are desirable. Examples will be described below. Example 1 Table 1 shows a comparison of the properties of various thermal spray materials sprayed by flame spraying using propane-oxygen and the properties of the sprayed films of the present invention and conventional products in an AOD furnace.

【table】

[Table] It can be seen that the product of the present invention, which is a combination of seawater magnesia clinker and Portland cement, is dense and significantly superior to conventional thermal sprayed materials. Example 2 Similar to Example 1, the AOD of the sprayed films when the product of the present invention was flame sprayed with propane-oxygen and when it was flame sprayed with conventional coke oxygen.
A comparison was made in a furnace. The blowing temperature of AOD furnace is 1700
℃ or above, the blowing time is about 120 minutes, and the slag basicity is
1.5, which is a condition that is difficult for furnace materials to withstand. Maguro bricks, dolomite bricks, and lime bricks are used for the lining, but the furnace materials around the tuyere and slag line are severely damaged, and this is the main reason for the furnace to shut down. For this reason, wet spraying repairs have been carried out on these damaged areas, but they do not last for one charge and there is no effective repair method. By thermal spray repair using coke-oxygen, as shown in Table 2, which shows a comparison between the inventive product and the conventional product, the conventional product has a service life of 1 charge, and although it has a repair effect, it is difficult to carry out repairs during daily work. There is a problem with the frequency of repairs becoming too high. Therefore, by thermal spraying the product of the present invention, it was found that it remained effectively in the tuyere and slag line portions until after three charges, and had a repair effect. In addition, 1.5 times the lifespan of conventional AOD furnaces has been secured.

[Table] * Durability around the tuyere, based on visual inspection.
As described above, the durability of the present invention has been confirmed even under severe operating conditions, and it is significantly superior to conventional thermal sprayed materials.

Claims (1)

[Claims] 1 A basic flame spraying product consisting of 50 to 95 parts by weight of one or more basic aggregates of magnesia, dolomite, and lime and 5 to 50 parts by weight of Portland cement, used for flame spray repair of steelmaking furnaces. Fireproof composition.