JPH07187818A - Flame spraying material - Google Patents

Abstract

PURPOSE:To enhance the adhesive strength to a surface to be repaired without damaging high corrosion resistance by compounding SiO2-containing sintered magnesite with a specific CaO-containing clinker. CONSTITUTION:10-90wt.% CaO type and/or MgO-CaO type CaO-containing clinker incorporating >=30wt.% CaO, and <=90wt.% the sum total of 10-90wt.% the sintered magnesite incorporating <=20wt.% magnesite and 1-10wt.% SiO2, and <=20wt.% the magnesite are compound as the flame spraying material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to MgO having excellent adhesiveness.
-CaO-based flame spray material.

[0002]

2. Description of the Related Art It is known to repair lining damage in industrial kilns such as converters, AOD furnaces, ladles, and vacuum degassing furnaces by flame spraying. According to this method, fine refractory powder is passed through a high-speed, high-temperature flame to be in a molten or semi-molten state and sprayed onto a damaged portion, and a dense and high-strength repair body structure can be obtained.

Conventionally, as a thermal spray material used for this flame spraying, a MgO-CaO system material has been proposed. For example, JP-A-63-107872 discloses a material comprising a calcareous clinker and a magnesia clinker.
Japanese Patent No. 107873 discloses a material further mixed with slag.

[0004]

[Problems to be Solved by the Invention] Among flame sprayed materials, M
The gO-CaO-based material is extremely excellent in corrosion resistance, and has become the mainstream of conventional materials for repairing industrial kilns. However, on the other hand, the adhesiveness (adhesive strength to the surface to be repaired) is not sufficient.

An object of the present invention is to improve the adhesiveness of a MgO-CaO flame spray material without impairing the high corrosion resistance of the flame spray material.

[0006]

Means and Actions for Solving the Problems In the present invention, 10 to 90 wt% of calcined magnesite containing 1 to 10 wt% of SiO ₂ as chemical components and 30 wt% of CaO as chemical components are used.
It is a flame spray material containing 10 to 90 wt% of CaO-containing and / or MgO-CaO-containing CaO-containing clinker contained above. Further, it is a flame spray material in which magnesite is mixed in the range of 20 wt% or less.

As a means for improving the adhesiveness of the thermal spray material,
For example, it is conceivable to add a low melting point substance such as K ₂ O, Na ₂ O, or slag, but if these are added in an amount sufficient to obtain a sufficient effect, the corrosion resistance is deteriorated.

On the other hand, the present invention uses Si as a chemical component.
O _2: Using the calcined magnesite containing 110 wt.%. The calcined magnesite is magnesium carbonate (MgC
It is a magnesite containing O ₃ ) as a main component, which has been calcined by a rotary kiln or the like at about 1000 ° C. or dead-burned at 1700 ° C. or higher to form MgO.
A porous structure is formed by decomposition of magnesium carbonate by firing.

In the present invention, by combining the calcined magnesite and the calcareous clinker in a specific ratio, the adhesiveness is remarkably improved. The reason is considered to be as follows. That is, the structure of the calcined magnesite is porous, the heat flow of the thermal spray flame penetrates into the pores, and the melting of SiO ₂ contained in the calcined magnesite is promoted. Then, SiO ₂ and Ca in this calcined magnesite
A low melt is generated by the reaction with the O-containing clinker, and the adhesion to the surface to be repaired is increased.

FIG. 1 is a graph showing the relationship between the material of the thermal spray material and its adhesiveness. In the graph, reference sign a is 50 wt% of calcined magnesite, CaO-containing clinker (C
aO: 97.25 wt%) In a thermal spray material of 50 wt%, there is a relationship between the ratio of the SiO ₂ component in the calcined magnesite and the adhesiveness of the thermal spray material. Reference sign b is seawater magnesia clinker 50 wt%, CaO-containing clinker (CaO: 9
This is the relationship between the ratio of the SiO ₂ component in the seawater magnesia clinker and the adhesiveness of the thermal spray material in the thermal spray material of 7.25 wt%) 50 wt%.

In the calcined magnesite, the content of SiO ₂ varies depending on the place of origin of the raw material magnesite and the beneficiation classification. As indicated by symbol a in the graph of FIG. 1, SiO
_It can be seen that the content of ₂ has a great influence on the adhesiveness.

The seawater magnesia clinker is a synthetic product, and the content of SiO ₂ can be freely controlled. However, seawater magnesia clinker is a dense tissue,
As shown by the graph of the symbol b, no significant change is observed in the adhesiveness of the thermal spray material even if the content of SiO ₂ is increased.

The test method of the adhesiveness in FIG. 1 was the same as the conditions shown in the section of Examples described later.

The calcined magnesite used in the present invention is S
An iO ₂ component having a content of 1 to 10 wt% is used. SiO ₂
If the content is less than 1 wt%, there is no adhesive effect, and 10 w
If t% is exceeded, MgO ・ SiO ₂・ CaO, 2MgO ・
Since excessively low-melting substances such as SiO ₂ are produced, the corrosion resistance is poor. Calcining magnesite MgO, because such SiO ₂ Besides _{Al 2 O 3, Fe 2 O} 3 is has been contained, not to lower the corrosion resistance of the thermal spray material, MgO, components other than SiO ₂ is in total 8wt % Or less is preferable.
The ratio of calcined magnesite in the thermal spray material is 10 wt.
If it is less than%, the corrosion resistance is lowered, and if it exceeds 90 wt%, the spalling resistance is poor.

In the present invention, the calcined magnesite and the magnesite may be used in combination. Magnesite is a natural mineral that has not been heat-treated. When a high-temperature flame is used during the use of a thermal spray material, magnesium carbonate decomposes, and the endothermic reaction due to the generation of carbon dioxide lowers the atmospheric temperature during thermal spraying, leading to a decrease in adhesion.
It is preferably not more than wt%. Further, in the case of using the calcined magnesite and the magnesite together, the total amount of the both must be 90 wt% or less from the viewpoint of spalling resistance.

A specific example of the CaO-containing clinker is a CaO substance containing 30% by weight or more of the chemical component CaO and / or
Alternatively, the quality is MgO-CaO. Dolomite clinker may be used as long as it is MgO-CaO. CaO is 30w
At less than t% clinker there is no adhesive effect. The ratio of CaO-containing clinker in the thermal spray material is 10 wt%
If it is less than the above, there is no effect in improving the adhesiveness. If it exceeds 90 wt%, the proportion of calcined magnesite decreases and the corrosion resistance decreases.

Like the conventional thermal spray material, the present invention further includes a melting aid, a solid fuel, chrome ore, magnesia, alumina, zircon, as long as the effect of the present invention is not impaired.
An appropriate amount of one or more selected from zirconia, spinel, carbon, carbide, nitride, lithium oxide, titania and the like may be blended. Of these, refractory raw materials are 80
You may mix up to wt%. As the melting aid, slag, metal powder, metal ore, talc, K ₂ O, Na ₂ O, Fe
_{It is 2} O ₃ , FeO, etc., and is effective in adhesion. The solid fuel is coal, coke, or the like, and has a melting promoting action by a combustion reaction in combination with oxygen gas.

The particle size of the thermal spray material is not particularly different from that of conventional materials. Considering the jettability from the nozzle, meltability by flame, etc., 1 mm or less, preferably 10 to 500 μm on average.
Is. The thermal spraying method is performed using a high-speed, high-temperature flame spraying apparatus using a gas such as propane gas, acetylene, hydrogen, kerosene, or a solid fuel such as liquid fuel or coke as a heat source as in the conventional method. As the carrier gas for the thermal spray material, for example, one kind or two or more kinds selected from oxygen, air, nitrogen, CO, CO ₂ , natural gas, argon and the like can be used. Also, various exhaust gases from the factory such as converter gas, hot stove gas, coke oven gas, etc. can be used.

The flame sprayed material of the present invention is, for example, a converter or AO.
D furnace, ladle, tundish, vacuum degassing furnace, mixing car, electric furnace, incinerator and other industrial kiln furnace lining formation, covering or repairing the lining, also used for forming, covering, repairing refractory articles, etc. it can.

[0020]

EXAMPLES Examples of the present invention and comparative examples thereof will be shown below. Table 1 shows the chemical analysis values of the blended raw materials used in each example. Table 2 shows the test results as well as the examples of the present invention and the comparative examples.

A propane-oxygen flame spraying apparatus was used for the spraying. The flame temperature is about 2500 ° C. at the highest temperature part. The thermal spray material is adjusted to have an average particle size of 100 to 150 μm and 3
It was fed into the flame at a rate of Kg / min. The surface to be sprayed was a vertical wall of MgO-C brick whose surface temperature was heated to 1200 ° C.

Adhesive strength: The shear strength between the material to be sprayed and the spray material was determined in an electric furnace at 1400 ° C.

Corrosion resistance: The thermal sprayed material after thermal spraying was cut out, and the size of thermal damage was determined by rotary erosion. The erosion agent was a combination of steel slab and converter slag in a weight ratio of 1: 1. The erosion dimension of Comparative Example 1 is shown as an index, and the larger the value, the larger the erosion dimension.

Spalling resistance: The surface structure was observed after spray cooling. ◯: No crevice, Δ: Small crevice, ×: Large crevice Durability (actual machine test); Hot repair of a 300 t converter lined with MgO-C brick was carried out to determine the number of durable charges.

[0025]

[Table 1]

[0026]

[Table 2]

As is clear from the test results shown in Table 2, the examples of the present invention exhibited the effect of excellent adhesion and spalling resistance in addition to the corrosion resistance originally possessed by the MgO-CaO material. . This effect was also confirmed by the durability in the actual machine test.

On the other hand, seawater magnesia clinker and C
Comparative Example 1 in which aO quality clinker is used in combination is inferior in adhesiveness and spalling resistance, and as a result, durability is not sufficient. Comparative Example 2 in which the proportion of calcined magnesite is more than the range of the present invention is inferior in corrosion resistance and spalling resistance. In Comparative Example 3, the total amount of calcined magnesite and magnesite exceeds the range of the present invention, and the spalling resistance is poor. Comparative Example 4 uses calcined magnesite having a SiO ₂ content lower than the limit range of the present invention, and is inferior in adhesiveness. Comparative Example 5 uses the calcined magnesite having a SiO ₂ content higher than the limited range of the present invention, and is inferior in corrosion resistance. Comparative Example 6 is MgO-C.
Since the aO quality clinker has a low CaO content, the adhesiveness is poor. Note that, for example, when the MgO-CaO clinker having a CaO content of 30 wt% or more is used as in Example 8, Mg having a CaO content of less than 30 wt% is further used.
The effect of the present invention can be obtained even by combining O-CaO clinker.

[0029]

The MgO-CaO thermal spray material is excellent in corrosion resistance, but is not sufficient in adhesiveness. The present invention solves this problem of adhesiveness, which results in MgO-
The original corrosion resistance of the CaO-based material is fully exerted, and the durability is significantly improved. As a result, for example, if the thermal spray material of the present invention is used as a repair material for a furnace, the effect of reducing the repair man-hour and repair material, and further improving the operation rate of the furnace is extremely large.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the material of a thermal spray material and its adhesiveness.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Takahashi 1-3-1 Niihama, Arai-cho, Takasago, Hyogo Prefecture Harima Ceramic Co., Ltd. (72) Inventor Kazuo Maeda 20-1 Shintomi, Futtsu-shi Nippon Steel Corporation Technology Development Headquarters (72) Inventor Tsuneo Kayama 20-1 Shintomi, Futtsu City Nippon Steel Co., Ltd. Technology Development Headquarters (72) Inventor Hideyuki Tsuda No. 1 Higashihama-cho, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Kurosaki Kiln Industry Co., Ltd. (72) Inventor Masataka Matsuo 1-1, Higashihama-cho, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Kurosaki Ceramics Co., Ltd.

Claims (2)

[Claims] 1. CaO-containing clinker 10 containing CaO and / or MgO—CaO containing 10 to 90 wt% of calcined magnesite containing 1 to 10 wt% of SiO _{2 as} a chemical component and 30 wt% or more of CaO as a chemical component. 90
Flame sprayed material blended with wt%. 2. A chemical component containing SiO _{2 in an} amount of 1 to 10 wt%, including 10 to less than 90 wt% of calcined magnesite, 20 wt% or less of magnesite, and 30 wt% of CaO as a chemical component.
A flame spray material containing the above CaO-containing and / or MgO-CaO-containing CaO-containing clinker in an amount of 10 to less than 90 wt% and the total amount of the above-mentioned calcined magnesite and magnesite being 90 wt% or less.