JPS6035311B2 - thermal spray material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal spray material having excellent corrosion resistance, adhesiveness, and thermal shock resistance and suitable for lining or repairing the walls of various industrial furnaces.

In recent years, thermal spraying has come to be used for lining or repairing the walls of industrial furnaces used in the steel industry.

This method involves passing a thermal spray material made of refractory powder through high-speed, high-temperature conditions, molten it, and spraying it onto the furnace wall, compared to the conventional method of spraying refractory powder mixed with a binder and water. Since the fineness and stability of the structure are significantly superior, the useful life of the furnace wall can be greatly extended. Conventionally, thermal spray materials used in this method are siliceous or alumina-siliceous materials that have a relatively low melting point because they can be easily melted.

However, with this material, the silica component foams during thermal spraying, making it impossible to obtain a dense structure, and its relatively low melting point does not provide sufficient corrosion resistance under harsh operating conditions, such as in steelmaking furnaces. . In addition, when the surface to be repaired is covered with slag, such as when repairing a molten metal container, adhesiveness (after adhesion to the furnace wall,
There was a problem in that the property (the property of not easily falling off during furnace operation) was significantly reduced. The present inventors aimed to resolve the above problems of conventional thermal spray materials.As a result of research, it was found that a thermal spray material that combines alumina and chromium raw materials in a specific ratio has excellent corrosion resistance and adhesion to furnace walls covered with slag. I found that it was extremely good.

Furthermore, we discovered that when magnesia alumina spinel is added to this material, the thermal shock resistance can be significantly improved, which led us to develop the present invention. That is, the present invention provides: (1) A thermal spray material for lining a furnace wall or repairing the same, consisting of 60-90% alumina and 10-40% chromium raw material by weight.

(2' Weight percentage of alumina 20-85%, chromium raw material 10-40%, magnesia alumina spinel 5
-40% thermal spray material for lining or repairing furnace walls.

It is.

Next, each raw material used in the thermal spray material of the present invention and its limited proportion will be explained in detail.

Note that all percentages shown below are percentages by weight. First of all, alumina has a large effect on improving wear resistance, and because of its relatively low melting point, it is a material necessary to impart adhesion to thermal spray materials (a property that causes less rebound loss during thermal spraying). Specific examples thereof include light calcined alumina obtained by calcining aluminum salt such as aluminum hydroxide at a temperature higher than the thermal decomposition temperature and lower than 165,000 ℃, loose alumina calcined at an even higher temperature, or haze fused alumina. In order to fully exhibit the above-mentioned effects of alumina, it is necessary to use alumina with a purity of 95% or more.

Chrome materials improve corrosion resistance because the component chromia (Cr203) is difficult to wet with molten steel and slag, and also exhibits excellent adhesion to furnace walls covered with slag, making them ideal for repairing molten metal containers. It is a particularly effective material in the case of

As the chromium-based raw material, chromium iron ore, magurolinker of Raidou or Agee, etc. can be used, and the chromia component is 20%.
% or more is preferable. Addition of magnesia alumina spinel linker has the effect of suppressing the growth of crystals in the post-sprayed structure of the thermal sprayed material, thereby imparting thermal shock resistance.

This spinel clinker is mainly composed of spinel mineral having the chemical formula of Mg○・A203, and is manufactured from alumina and magnesia by a light sintering method, a competitive coalescence method, or a melt synthesis method.

Of these, Mg is used as a chemical component in the present invention.
It is preferable that ○ is in the range of 10 to 70%. The present invention is made by combining the above materials, and in the case of the first invention, the respective ratios are 60 to 90% alumina and 10 to 90% chrome material.
If the alumina content is less than 60% and the chromium material exceeds 40%, the abrasion resistance and adhesion properties of alumina will be lost, and at the same time, the chromium material will increase and the structure between the irradiated layers will become loose. So I don't like it.

If the alumina content exceeds 90% and the chromium raw material content is less than 10%, the alumina content will increase, resulting in poor corrosion resistance, and the chromium raw material content will be insufficient, resulting in insufficient adhesion to the furnace wall with slag attached. The proportion of the magnesia alumina spinel linker is 5 to 40%; outside this range, crystals in the sprayed layer will develop and the thermal shock resistance will deteriorate.

In addition, when this magnesia alumina spinel clinker is blended, the appropriate proportions of other materials are 20 to 85% alumina and 11% chromium raw material.
It becomes 0-40%.

The particle size of the material is adjusted to a weight average diameter of about 30 to 100 French, taking into consideration supplyability during port firing, melting degree, etc.

Further, if necessary, the alumina particles may be heat-treated at a temperature of 1650 CO or less, and other materials may be attached to the surface of the alumina particles. Next, we listed a thermal spray material having the composition of the present invention, as well as a comparative thermal spray material that does not belong to the spray material composition of the present invention, and a conventional alumina-silica thermal spray material, and measured various physical properties for each. , the results are shown in Tables 1 and 2.
Shown in the table.

Table 1 Note) Lightly calcined alumina; 1300 qo of aluminum hydroxide
×Su: “I got it by firing.

Lightly calcined spinel: obtained by mixing magnesium hydroxide and aluminum hydroxide and calcining at 1500°C x r.

Table 2: Mixing ratio and physical properties of each example! 〇． ．． ．． Strong adhesion △…Normal adhesion ×・
・Rotary erosion method where peeling was observed in some parts of the adhesive layer (
Converter slag 100%, 1700℃ x 3hrs) ※※※
Condition of sample cross section after thermal spraying and air cooling As shown in Table 2, conventional alumina-silica materials have silica and potassium feldspar added to them to improve thermal shock resistance, but these silica compounds are The molded product cannot be obtained as a dense molded product due to foaming, and its resistance to molten slag is significantly reduced.

Furthermore, in the comparative example, the ratio of alumina, chromite, and spinel was not appropriate, resulting in poor adhesion, thermal shock resistance, etc., and the durability of the thermal sprayed material could not be improved. On the other hand, Examples 1 and 2 of the present invention are both delicate and have excellent insect resistance and adhesion to walls with slag, and Examples 3, 4, and 5 of the present invention have a crystal structure due to the addition of spinel. We were able to impart thermal shock resistance to suppress growth.

When Examples 1 and 4 of the present invention were sprayed onto a green groove tube of a vacuum degassing device, they showed 10 to 15 times the durability compared to the conventional alumina IJ thermal spray material.

Claims (1)

[Scope of Claims] 1. A thermal spray material for lining a furnace wall or repairing the same, consisting of 60-90% alumina and 10-40% chromium raw material by weight. 2 Weight percentage of alumina 20-85%, chromium raw material 10-40%, magnesia-alumina spinel 5-4
0% thermal spray material for lining or repairing furnace walls.