JPS60215579A - Basic refractory composition for flame spraying - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a basic refractory composition for flame spraying (hereinafter simply referred to as thermal spraying material) used for flame spraying repair of steelmaking furnaces such as converters, electric furnaces, AOD furnaces, VOD pans, and RH. ) regarding.

In recent years, flame spray repair has begun to be widely considered as an alternative to conventional wet repair, and flame spray has begun to be put into practical use in steelmaking furnaces such as converters, AOD furnaces, and RH. 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 and magnesia are used in solid fuel-oxygen flame spraying. It is difficult to melt high melting point basic materials such as magnesia, dolomite, and lime with these thermal spraying methods, so various low melting point substances such as the above-mentioned alumina, LD slag, and coke ash are added to melt high melting point basic materials. This makes it easy to adhere.

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, magnesia-alumina or dolomite-
The disadvantage of alumina and thermal sprayed materials is that when used at high temperatures in oxygen blowing vessels such as converters and AOD furnaces, and under operating conditions where the slag basicity is 1 or more, the corrosion resistance of the sprayed layer is poor and the durability is insufficient. .

Furthermore, although the magnesia-LD slag thermal spray material has high corrosion resistance against the slag of the oxygen blowing vessel of the converter or AOD furnace, it has low hot strength and has 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.

The thermal spraying material of the present invention contains one or more of magnesia clinker, dolomite clinker, and lime clinker whose particle size is adjusted to less than II+2++! θ~de left weight part and por) f whose particle size was similarly adjusted to 1 m or less
This is a basic material for flame spraying consisting of 5 parts by weight of child cement.

Magnesia clinker, dolomite clinker 1 The lime clinker is not particularly limited, and may be natural or synthetically produced.

The particle size is preferably /WI or less and dried. When the grain size is larger than 1, there is a drawback that rebound loss is large and the construction yield is reduced.

Preferably, the content of fine powder of 10μ or less is 20% or less, and if it exceeds 1.20%, the conveyance of the material will decrease and the material will be discharged unevenly during thermal spraying, and the thermal sprayed layer will have a dense layer and a porous layer. This makes it easier 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. Portland cement OaO/Sin,
The molar ratio is usually about 3, and the main mineral composition is tricalcium silicate, which has a high melting point, so the OaQ/5in2 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 0aO6Ochi or more and SiO□ηJ or less, and other components account for 75%.
The particle size of Portland cement is preferably ioμ 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 recommended to adjust the settings and use it accordingly.

The particle size of Portland cement is preferably 100 to 10 microns from the viewpoint of transportability and meltability.

If the particle size is 1,000 μm or more, the meltability is poor, and if the particle size of less than 10 μm increases, the transportability will deteriorate. Therefore, it is desirable that the proportion of particles smaller than ioμ is 20% or less. Examples will be described below.

Example l Properties of various thermal spray materials sprayed by flame spraying using propane-oxygen, and AO of properties of sprayed films of the present invention and conventional products
Table 1 shows a comparison in Furnace D.

(G) Part 1 It can be seen that the product of the present invention, which is a combination of surface seawater magnesia and Portland cement, is dense and significantly superior to conventional thermal spray materials.

Example 2 In the same manner as in Example 1, the thermal sprayed films obtained when the product of the present invention was flame sprayed using propane-oxygen and when the product was flame sprayed using conventional coke oxygen were compared in an AOD furnace.

In the AOD furnace, the blowing temperature is 7700° C. or higher, the blowing time is about 720 minutes, and the slag basicity is extremely low, which are conditions that are difficult for the furnace material to withstand.

Maguro bricks, dolomite bricks, or lime bricks are used for the lining, but the furnace materials around the tuyere and slag line are severely damaged, which 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 the l-charge has no durability and there is no effective repair method.

As a result of thermal spray repair using coke-oxygen, as shown in Table 1, which shows a comparison between the inventive product and the conventional product, the conventional product can last for 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 parts until after three charges, and had a repair effect.

In addition, j times the lifespan of the conventional AOD furnace can be secured.

Chapter - Table (Blending unit, parts by weight) *Durability around the tuyeres, based on visual inspection.

As described above, the present invention is recognized to be durable even under severe operating conditions, and is significantly superior to conventional thermal spray materials.

Patent Applicant: Shinagawa Shiro Brick Co., Ltd., Nippon Steel Tube Co., Ltd., Nippon Sanso Co., Ltd. (Ir) Procedural Amendment Date: February 12, 1985 Commissioner of the Patent Office: Shiga Gakudon 1, Indication of Case: Patent Application No. 67461, filed in 1988 2. Name of the invention Name of basic refractory composition for flame spraying (412> Nippon Kokan Co., Ltd. 4, Agent 〒100 Address 4th Floor 5, Marunouchi Building, 4-1 Sara-chome, Marunouchi, Chiyoda-ku, Tokyo, Subject of amendment (1) ) Column 6 of Detailed Description of the Invention in the Specification, Contents of Amendment (1) "Seawater magnesia" in lines 5 and 16 of page 6 of the specification is amended to read "seawater magnesia clinker."

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Claims (1)

[Claims] ls of basic aggregates of magnesia, dolomite, and lime
Or a basic refractory composition for flame thermal spraying consisting of 30 to 93 parts by weight of two or more types, and 2 to 3 parts by weight of Portland cement.