JPH0764650B2 - Spray repair material for metal refining furnace - Google Patents

Description

TECHNICAL FIELD The present invention relates to a spray repair material for a metal refining furnace.

Conventional technology and its problems In recent years, in metal refining furnaces such as converters, magnesia-carbonaceous bricks with excellent durability have come to be used as lining materials, and local erosion damage such as slag line parts is repaired. The life of the furnace has come to be greatly affected. Conventionally, the spray repair method has been mainly used to repair the locally melted portion. This is a method of forming a repair layer by mixing a mixture of a refractory raw material and a binder (spray material) with water at the tip of a spray nozzle and spraying the mixture on a furnace wall. As a conventional spray material, the workability at the time of spraying, especially the adhesion to the furnace wall, is emphasized,
Highly viscous and fast containing basic refractory raw materials such as magnesia, dolomite, magnesia-dromite (hereinafter referred to as magdro), binders such as phosphates, and hardeners for phosphates such as ultrafine powder of magnesia and lime compounds. Curable materials have been mainly used. However, 1) these repair materials have insufficient durability and hot strength, 2)
Due to the recent changes in operating conditions, melting of steep slopes such as trunnions has disappeared, and only mildly sloped parts such as slag lines have melted, so repairs with low viscosity and slow hardening are possible. The material has come to be desired.
This is because the low-viscosity and slow-hardening repair material boils during hot working, so filling and drying proceed at the same time, making the working body dense, and improving the durability and strength of the working body. This is because it has the advantage of Therefore, in order to obtain a slow-curing repair material, a material in which a phosphate curing agent is not added to the components of the conventional repair material is used, but the following drawbacks are not preferable. That is, when dolomite-containing raw materials such as dolomite and magdolo are used, water-insoluble polymer phosphate reacts with calcia that is eluted from the dolomite raw material during the boiling period of the material and sodium phosphate that is a binder. Is generated, which causes a problem that the curing is accelerated. On the other hand, the magnesia raw material has poor reactivity with sodium phosphate, but lacks in durability, especially volume stability in the hot state, and has large slag penetration, so that structural spalling is prominent. It has the disadvantage that it is inferior to the material.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in view of the problems of the above-mentioned conventional techniques, and as a result, even if the Magdoro raw material is used as a refractory aggregate, it does not contain condensed phosphoric acid and phosphorus. In combination with an alkaline salt of the electrolyte, and by adding a sparingly water-soluble calcium phosphate in order to prevent a decrease in hot strength of the spraying material due to containing an alkali, slow curing,
The inventors have found that a spray repair material for a metal refining furnace, which is extremely excellent in durability such as corrosion resistance and has a high adhesive strength with a furnace wall, can be obtained, and completed the present invention.

That is, the present invention is a refractory raw material 100 parts by weight consisting of dolomite raw material 30 to 70% by weight and magnesia raw material 70 to 30% by weight, condensed sodium phosphate 2.5 to 7.0 parts by weight, strong electrolyte alkali salt 0.2 to 1.5 parts by weight and Slightly soluble calcium phosphate 0.3〜
It relates to spray repair material for metal refining furnace containing 1.5 parts by weight.

In the present invention, dolomite raw material and magnesia raw material are used as the refractory raw material.

As the dolomite raw material, any of those commonly used in this field can be used, but normally a calcia content of 40% or more and a bulk specific gravity of 3.20 or more are used. However, considering the volume stability of the material, the slag permeation-preventing property, etc., the calcia content is particularly preferably 55% or more. The amount of dolomite raw material is preferably about 30 to 70% by weight of the total amount of refractory raw material. If it is less than 30% by weight, the effect of calcia is hardly exerted, while if it exceeds 70% by weight, due to dusting, dolomite fine powder cannot be used, so the grain size composition limits the spraying workability and corrosion resistance. Etc. will decrease.

As the magnesia raw material, those commonly used in this field such as seawater magnesia, electrofused magnesia and natural magnesia can be used, but normally, magnesia content 92%, SiO ₂ content 5% or less, CaO / SiO ₂ = 0.3 or more. use.

The particle size of the refractory raw material is not particularly limited and may be appropriately selected. Usually, coarse particles having a particle size of 5 to 1 mm are about 30 to 50%, and particle size 1
It may be used by containing about 20 to 40% of intermediate particles of mm or less and about 20 to 40% of fine powder of 0.074 mm or less. However,
Considering the dusting of the material, it is desirable not to use dolomite fine powder having a particle size of 0.074 mm or less.

In the present invention, the curing of the repair material is delayed by using the condensed sodium phosphate in combination with the alkali salt of the strong electrolyte containing no phosphorus. This utilizes a salting-out phenomenon, that is, the solubility of two types of strong electrolyte salts in water is influenced by the concentration of each other, and is usually lower than that of a single substance. The reaction is delayed, in which the sodium ion of the water-soluble sodium phosphate is replaced with the Ca ion in the material to form a water-insoluble polymer phosphate.

As the condensed sodium phosphate, any ordinary one can be used, and examples thereof include sodium pyrophosphate, sodium tripolyphosphate, sodium tetraboriphosphate, sodium hexametaphosphate and the like. The blending amount is preferably about 2.5 to 7.0 parts by weight with respect to 100 parts by weight of the refractory raw material. If it is less than 2.5 parts by weight, sufficient adhesive strength will not be exhibited in the initial stage of use, while if it exceeds 7.0 parts by weight, the amount of flux in the material will increase and corrosion resistance will decrease.

As the alkali salt of a strong electrolyte containing no phosphorus, any of a weakly acidic to weakly basic sodium salt or potassium salt having a solubility of 10 or more can be used, for example, chlorides such as NaCl and KCl, Na ₂ CO ₃ , Examples thereof include carbonates such as K ₂ CO ₃ and acetates such as CH ₃ COONa. The blending amount thereof is preferably about 0.2 to 1.5 parts by weight with respect to 100 parts by weight of the refractory raw material. If it is less than 0.2 parts by weight, the curing retarding effect is poor, while if it exceeds 1.5 parts by weight, the amount of phosphate dissolved decreases, and the strength after drying becomes difficult to develop, and C
Since it has a component that decomposes during heating, such as l and CO ₂ , problems such as explosion during heating and deterioration of corrosion resistance occur.

As the poorly water-soluble calcium phosphate, any ordinary calcium phosphate can be used, and examples thereof include dibasic calcium phosphate, tribasic calcium phosphate, and pyrophosphate calcium. The blending amount is 0.3 to 100 parts by weight of the refractory raw material.
It should be about 1.5 parts by weight. If it is less than 0.3 parts by weight, the effect of improving the hot strength is small, while if it exceeds 1.5 parts by weight, the effect is not so changed and it is uneconomical.

The repair material of the present invention, a predetermined amount of each of the above raw materials, according to a conventional method,
For example, it is produced by mixing with an Erich mixer or the like.

In repairing the melted point using the repair material of the present invention, any spray repair method performed in this field can be adopted.

EFFECTS OF THE INVENTION The spray repair material for a metal refining furnace of the present invention has extremely excellent corrosion resistance and adhesion strength to the furnace wall, and exhibits remarkably high durability.

Examples The following examples and comparative examples will further clarify the present invention.

Examples 1 to 5 and Comparative Examples 1 and 2 To 100 parts by weight of the refractory raw material, each raw material was added at a mixing ratio (parts by weight) shown in Table 1, and mixed by an Erich mixer.
The repair material of the present invention and a conventional repair material were manufactured. As the dolomite raw material, natural dolomite with a calcia content of 58% and a bulk specific gravity of 3.25 was used.As the magnesia raw material, magnesia content of 94%, SiO ₂ content of 2.5%, seawater magnesia of CaO / SiO ₂ = 0.4, and condensed phosphoric acid were used. As the material, sodium tetrapolyphosphate having a Na ₂ O content of 23% and a P ₂ O ₅ content of 63% was used.

After kneading the obtained repair material with water, it was poured into a brick frame heated to 1200 ° C. in an oxygen-propane furnace, and its hardening property was determined, and a construction body sample to be subjected to the quality test described later was prepared. . The size of the sample is 170 × 300 × 60 mm, and the brick with a 170 × 300 mm surface is a brick frame (dolomite,
250 x 350 x 110 mm). Slag coating was applied to the surface of the brick in advance so that the construction body (repair layer) was bonded to the brick through the slag surface. With respect to the obtained construction body sample, the denseness and the corrosion resistance were examined. As the denseness test, the porosity and bulk specific gravity were measured according to JISR-2205. As a corrosion resistance test, a crucible type sample with an outer dimension diameter of 50 mm × height of 50 mm and a concave dimension diameter of 20 mm × height of 20 mm was cut out from the construction body sample, and 30 g of converter slag was filled into this sample, which was then oxygen-containing. After firing in a propane furnace at 1700 ° C. for 3 hours, the crucible type sample was cut in the vertical direction, and the erosion area due to slag and the permeation area of slag were measured. The adhesive strength was measured by cutting out a sample having a size of 40 × 40 × 120 mm consisting of a laid brick and a construction body, and performing a room temperature bending strength test centering on the adhesive interface according to JIS R-2213. The results are shown in Table 1.

It can be seen from Table 1 that the repair material of the present invention has a longer curing time, is superior in denseness, is superior in corrosion resistance, and is superior in adhesive strength to the conventional repair materials.

Claims (1)

[Claims] 1. A refractory raw material consisting of 30 to 70% by weight of dolomite raw material and 70 to 30% by weight of magnesia raw material, 2.5 to 7.0 parts by weight of condensed sodium phosphate, and an alkali salt of a strong electrolyte containing no phosphorus of 0.2 to Spray repair material for metal refining furnace containing 1.5 parts by weight and 0.3 to 1.5 parts by weight of sparingly soluble calcium phosphate.