JP2733644B2 - Non-phosphoric acid spray repair material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a repair material for hot repairing a locally damaged portion of a steelmaking furnace such as a steelmaking furnace, a melting furnace, a rotary furnace, an electric furnace or various steelmaking containers such as a ladle. More specifically, the present invention relates to a non-phosphoric acid-based spray repair material suitable for repairing a wrought steel container having a low gas mixing rate.

[0002]

2. Description of the Related Art The inner walls of various steelmaking furnaces and vessels for steelmaking are locally damaged by wear caused by molten steel or hot metal, erosion by slag, and the like, thereby significantly shortening the life of the entire furnace. Therefore, for damage such as cracks, falling off, and melting that occurred during operation, hot spray repairs and the like are performed urgently to extend the life of the furnace and protect the furnace body.

In the spray repair, a spray repair material is adhered to a necessary portion by using a spray gun, and the repair material can be reliably supplied to the repair portion and repair can be performed without interrupting the operation of the furnace. In this case, the spray repair material is required to have the following characteristics. That is, (1) it has fluidity and slurry suitable for operability during repair, (2) it has excellent slag resistance as resistance to slag erosion, and (3)
It has high adhesion between the damaged part and the repair material, and has a sponging resistance that forms a strong structure by sintering under the conditions of use; (4) excellent durability at high temperatures; (5) spraying material Characteristics such as no contamination of molten steel by the

[0004]

In general, a binder is blended into a spray repair material to impart fluidity and slurry to the repair material at the time of repair operation and to maintain strength at a working temperature after construction. ing. Regarding the above (1), (2) and (3), in addition to inorganic compounds such as phosphates as binders,
Organic binders such as MC, MC, PVA, dextrin, and pulp waste liquor are blended. In particular, phosphates have been widely used because they have excellent hot strength, have high peptizing power, and can ensure wettability to a sprayed body. However, when phosphoric acid is added to the spray repair material, the molten steel is contaminated by phosphoric acid,
This contradicts the required characteristics of the above (5). In particular, the phosphoric acid component is not a preferable component at the present time when the dephosphorization process is adopted because the quality of the steel deteriorates in the steel making process.
The requirements are particularly strong in the manufacturing process and ladle of special steel such as stainless steel. On the other hand, when another binder is used, the durability at a high temperature is lacking, and the property of (4) cannot be satisfied. In addition, spray repair is not only an effect of emergency treatment for a damaged portion during furnace operation, but also the durability and heat resistance of a repair material having a high residual ratio even after two charges by one spray repair is expected. In a steel type in which a process such as RH degassing, which has been widely used in recent years, is performed, the tapping temperature is as high as 1700 to 1800 ° C., which is excellent in satisfying the above (2), (3), and (4). Repair materials that satisfy durability and heat resistance are required. However, the residual ratio of the repair material depends on the operating temperature of the furnace, and at a high tapping temperature of 1800 ° C., the residual ratio of the conventional spray repair material is almost 0% even after one charge. As described above, in a situation where high-purity refining is being demanded, the development of a non-phosphoric acid-based spray repair material that has excellent high-temperature durability and high-temperature adhesion and does not contaminate molten steel is strongly demanded. ing.

[0005]

Means for Solving the Problems The present inventor has conducted intensive studies in view of the above circumstances. As a result, by adjusting the pH of the compounding components, excellent repair material densities and deflocculation properties were obtained. They have found that workability at high temperatures can be ensured, and have completed the present invention.

That is, the present invention relates to (a) MgO aggregate 10
(B) special dolomite aggregate having a CaCO ₃ coating layer or dolomite aggregate containing 40% by weight or more of CaO component, (c) silicate 1
-10% by weight, (d) calcium carbonate 1-10% by weight,
(E) A non-phosphoric acid-based spray repair material comprising 1 to 5% by weight of ultrafine silica powder and (F) 0.1 to 3.0% by weight of magnesium sulfate. Hereinafter, the present invention will be described in detail.

In the non-phosphoric acid-based spray repair material of the present invention, Mg
As the O-aggregate, those conventionally used generally can be used. The particle size is not particularly limited, but the particle size is preferably about 7 mm or less, particularly preferably 5.0 mm or less from the viewpoint of strength, fluidity, and filling property of the obtained repair material. . The blending amount is 10
The range is preferably from 70 to 70% by weight, particularly preferably from 10 to 70% by weight.
It is in the range of 50% by weight.

In the non-phosphoric acid-based spray repair material of the present invention,
Special dolomite aggregate or Ca with CO ₃ coating layer formed
Dolomite aggregate containing 40% or more of the O component can be used. The particle size of the dolomite aggregate is not particularly limited, but is preferably 7 mm or less, particularly preferably 5 mm or less for the same reason as the MgO aggregate. As the dolomite aggregate, a special dolomite aggregate that has been subjected to surface treatment with carbon dioxide gas in order to enhance digestion resistance is used. Here, as the surface treatment with carbon dioxide gas, dolomite aggregate or synthetic dolomite aggregate is left in an atmosphere having a carbon dioxide gas concentration of 80% or more and a temperature of 400 to 800 ° C. for about 3 to 6 hours, and the surface thereof is carbon dioxide gas. CaCO ₃
A method of forming a coating layer is suitably employed. Forming C
The thickness of the aCO ₃ coating layer is preferably from 0.8 to 1.0 μm, and sufficient digestion resistance can be obtained within this thickness range. In addition, a dolomite aggregate containing CaO can be used instead of the special dolomite aggregate having the CaCO ₃ coating layer formed thereon. CaO reacts with a silicate component blended in the non-phosphoric acid-based spray repair material to form 3CaO.SiO ₂ having high hot strength in a high temperature range. Heretofore, since the SiO ₂ component forms a liquid phase with the MgO component at a high temperature, sufficient hot strength cannot be secured. However, in the present invention, 3CaO.SiO ₂ is formed by actively incorporating the CaO component. For this purpose, CaO is preferably contained at a high concentration of 40% or more. The amount of the special dolomite aggregate formed with the CaCO ₃ coating layer or the dolomite aggregate containing CaO component of 40% or more is 20 to 7%.
A range of 0% by weight, particularly, closer to 70% by weight is more preferable.

Other components to be added to the non-phosphoric acid-based spray repair material of the present invention include silicate, calcium carbonate, ultrafine silica powder, and magnesium sulfate. These components are mixed with the MgO aggregate and the dolomite aggregate. When 5.00 g of this mixture is put into 500 ml of pure water stirred with a magnetic stirrer, and the pH is measured every 10 seconds, the pH is in the range of 8.5 to 10.5 for about 10 seconds. When the PH after 1 second is in the range of 10.5-11.5, appropriate slurry properties and binding properties as a non-phosphoric acid-based spray repair material are usually obtained. That is, the gelation of the water glass formed by the blending components can be prevented, and the prevention of gelation can ensure the peptizing power. In addition, the amount of water added can be reduced by securing the peptizing power, and a dense layer of the repair material can be formed. In particular, the formation of a dense layer due to low water content makes 3CaO due to the reaction between dolomite and silicic acid.
-The formation of SiO ₂ is smoothly promoted, and the
Various effects such as prevention of slag penetration due to a decrease in porosity also occur. In addition, the improvement of the peptizing property can ensure the wettability to the sprayed body. On the other hand, since the alkali does not show strong alkali at the initial stage and the alkalinity increases with time, the gelation of the water glass progresses with the lapse of time, and the hard glass retains its shape. That is, the repair material after being attached to the sprayed body is subjected to alkali ions released from the MgO aggregate and the dolomite aggregate, whereby the water glass is gelled, and the shape is retained and hardened. This ensures the workability at high temperatures, which has been considered difficult in the past, in addition to the coagulation effect of the ultrafine silica powder. The sintering reaction is promoted by the addition of magnesium sulfate, and a remarkable improvement in durability at high temperatures can be obtained. The amount of these components is 1 to 10% by weight of silicate, 1 to 10% by weight of calcium carbonate, 1
-5% by weight and 0.1-3% by weight of magnesium sulfate are preferred. The ultrafine silica powder is not strictly defined by the average particle diameter, but generally refers to silica powder having an average particle diameter of 0.20 μm or less.

[0010] In producing the non-phosphoric acid-based spray repair material of the present invention, there is no particular limitation, and it can be produced by an ordinary method. For example, a predetermined amount of the components may be mixed and kneaded with a roll pan or the like.

The method of using the non-phosphoric acid-based spray repair material of the present invention is not particularly limited, and can be used in the same manner as a conventional spray repair material, and can be sprayed on damaged parts such as a rotary furnace and an electric furnace. Repair materials are injected with a gun, and spray repair is performed hot.

[0012]

EXAMPLES The present invention will be described in detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

(Examples 1 and 2, Comparative Examples 1 and 2: Hot Bending Strength) Various components having the mixing ratios shown in Table 1 were kneaded with a roll pan to produce a spray repair material. 800
, 1200 ° C, and 1400 ° C, and the hot bending strength at each temperature was measured. As a result, although the conventional product shown in the comparative example had a high hot bending strength at a low temperature, the strength decreased as the temperature rose. However, in the product of the present invention, excellent bending strength at a high temperature was observed.

(Example 3, Comparative Example 3: Workability and Durability) After preparing a spray repair material having the same composition as in Example 1 and Comparative Example 1, it was used in an actual furnace to adhere, peel, and hop. The workability such as the above and the residual ratio after one charge and after two charges were measured. The construction conditions are shown in Table-2 and the results are shown in Table-3. With the conventional product, small peeling was observed during construction,
The product of the present invention had good adhesion and no peeling was observed. Further, the conventional product had a residual rate of 0% after 1 charge at a temperature condition of 1800 ° C., while the product of the present invention had a residual rate of 30% even after 2 charges, and was excellent at high temperatures. Service life was observed.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

The non-phosphoric acid-based spray repair material according to the present invention comprises:
Since it does not contain phosphoric acid as a binder, there is no mixing of phosphoric acid into molten steel. Therefore, if used for repairing a smelted steel container, spray repair can be performed without contaminating the smelted steel.
In the present invention, the pH is adjusted by the compounding components to ensure the peptizing power of the water glass. For this reason, a spray repair material is prepared with a low moisture content, and a high density spray repair material is generated, and the formation of durable 3CaO.SiO ₂ at high temperatures is promoted, and the sintering reaction is promoted by blending magnesium sulfate. 1800 ° C in combination with the coagulation reaction of ultrafine silica powder
It has excellent durability even at high and low temperatures. in addition,
When the non-phosphoric acid-based spray repair material of the present invention is used, it is possible to maintain a high residual ratio even after 2 charges by one spray repair as well as an emergency treatment for a damaged portion during furnace operation. it can.

Claims (1)

(57) [Claims] 1. (a) 10-70% by weight of MgO aggregate,
(B) a special dolomite aggregate formed with a CaCO ₃ coating layer or a dolomite aggregate containing 40% by weight or more of CaO component, 20 to 70% by weight, (c) 1 to 10% by weight of silicate,
(D) 1 to 10% by weight of calcium carbonate, (E) 1 to 5% by weight of ultrafine silica powder, and (F) magnesium sulfate.
A non-phosphoric acid spray repair material consisting of 1 to 3.0% by weight.