JPH08224657A - How to build a furnace - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a method for easily constructing a lining of a refractory lining that is highly durable and has a controllable lining thickness by improving a thermal spray material and a method for constructing a furnace. According to the present invention, a refractory powder having a particle diameter of 300 μm or less that completely melts in a flame of 2300 ° C. at a flame temperature of 70% by weight to 90% by weight and a particle diameter of 1 mm to 5 mm in which only the surface melts in the flame A flame-sprayed material comprising 10% by weight or more and 30% by weight or less of the following refractory powder is adhered to a molten metal refining furnace iron shell or a permanent lining lined with the iron shell by a flame spraying method to form an internal refractory material. , The part where the refractory is applied is surrounded by the molten metal refining furnace iron skin or the permanent lining lined in the iron skin and the shape retaining plate, and flame spraying is performed by performing flame spraying in a direction parallel to the molten metal refining furnace iron skin. The material is applied to a molten metal refining furnace iron shell or a permanent lining lined with the iron shell to form a refractory lining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a refractory lining for a molten metal refining furnace such as a ladle and a secondary refining furnace.

[0002]

2. Description of the Related Art A typical method of constructing a refractory in a molten metal refining furnace is so-called brick laying work by a furnace builder. As the smelting furnace becomes larger and the productivity increases, it is required to speed up the construction of the refining furnace and save labor, but it is difficult to mechanize the construction of the furnace using refractory bricks. Therefore, various construction methods using powdery amorphous refractory or a furnace construction method utilizing a flame spraying method have been developed to save labor and mechanize the furnace.

Conventionally, when a refractory lining for a metal refining furnace is constructed by a flame spraying method, a sprayed layer is continuously laminated. When such a laminating method is performed, there is a problem that the lined thermal sprayed layer forms an integral wall surface, and cracks are generated in the cooling process after thermal spraying to separate from the metal refining furnace. Therefore, as disclosed in Japanese Patent Publication No. 58-6874, a flame-sprayed layer of refractory is divided into zones on the surface of a permanent lining such as a refractory brick lined in the outer skin of a metal refining furnace to construct a furnace. It is also proposed.

[0004]

However, dividing the sprayed layer of the refractory material and constructing the furnace can hinder automation of the furnace construction. Further, it is difficult to apply a lining with a constant thickness. Therefore, an object of the present invention is to provide a method for easily constructing a lining of a refractory lining that has a high durability and is capable of controlling a lining thickness by improving a thermal spray material and a method for constructing a furnace.

[0005]

In order to achieve the above object, the present invention focuses on a thermal spray material and has a particle size of 300 μm which is completely melted in a flame having a flame temperature of 2300 ° C. at least.
A flame spraying method is used to form a thermal spray material comprising 70% by weight or more and 90% by weight or less of the following refractory powder and 10% by weight or more and 30% by weight or less of the refractory powder having a particle diameter of 1 mm or more and 5 mm or less that melts only in the flame. Molten metal refining furnace To form a refractory lining by adhering to a permanent lining such as iron shell or refractory brick lined with iron skin, and further focusing on the furnace construction means, refining the portion where the refractory is constructed with molten metal refining Enclosed by a permanent lining such as a furnace iron skin or a refractory brick lined with an iron skin and a shape retaining plate, and performing flame spraying in a direction parallel to the molten metal refining furnace iron shell, the sprayed material is molten metal refining furnace iron. It is characterized by forming a refractory lining by adhering it to a permanent lining lined in leather or iron skin.

[0006]

The furnace construction method of the present invention utilizes the flame spraying technique. The flame spraying technology was originally developed as an efficient repair technology for kilns, and it forms a refractory layer by passing it through a flame and adhering the molten refractory material to the furnace wall surface in a molten state. It is a technology. This technique has the following features.

1) Since the refractory particles collide in a molten state, the adhesion is good, the adhesive strength is high, and the material loss during construction is small. 2) Since the formed work body has a dense bond with the furnace wall and high strength, there is no risk of peeling during operation, and it is not easily eroded by molten steel or slag during refining. However, although there is no problem in the case of repairing by performing thermal spraying locally, solidification shrinkage becomes large when constructing the furnace by spraying the entire lining, and it is necessary to take measures to prevent cracks caused by this. Therefore, the present invention provides the following measures.

First, the present invention focused on the thermal spray material. That is, it was considered that the thermal spray material should be composed of particles that completely melt in the flame and particles that hardly melt in the flame. In particular,
When powder (coarse particles) having a particle diameter of 1 mm or more is present in the thermal spray material, the coarse particles are hardly melted in the flame and only the surface is melted and the coarse particles are buried as they are in the thermal spraying work body. Then, it was found that the solidification shrinkage was smaller than that when the coarse particles were not buried, and the propagation of cracks generated during the solidification shrinkage was blocked at this coarse particle portion. In the present invention, the ratio of the refractory powder having a particle diameter of 1 mm or more and 5 mm or less in the thermal spray material is set to 10% by weight or more because the propagation of cracks generated during solidification shrinkage can be prevented within this range. If it is less than 10% by weight, the number of coarse particles that prevent the growth of cracks is small, so that the propagation of cracks cannot be sufficiently prevented. Further, the ratio of the refractory powder having a particle diameter of 1 mm or more and 5 mm or less is set to 30% by weight or less is 30% by weight.
At the same time, it is included in the thermal spraying material at the same time, and fine refractory powder with a particle size of 300 μm or less intended to be completely melted in the flame becomes insufficiently melted in the flame, and a strong construction body cannot be formed. Is.

The particle size of the refractory powder added to prevent the growth of cracks is set to 1 mm or more and 5 mm or less because the effect of preventing the growth of cracks is small when the size is less than 1 mm, and the work body is more than 5 mm. Because it is hard to be buried. The refractory powder that is completely melted in the flame has a particle size of 300 μm or less because if the particle size exceeds 300 μm, it may not be completely melted while passing through the flame. Refractory powders used as thermal spray materials include Al2 O3 and Mg with a Zegel cone melting point of 26 or higher.
O, chromite ore, spinel, etc. are applicable. On the other hand, the flame temperature is set to at least 2300 ° C. because this temperature is necessary at least in order to melt the refractory material in the flame.

Next, focusing on the means of furnace construction by thermal spraying, the method will be described in detail. In the conventional method of spraying the refractory by spraying in the vertical direction on the iron shell of the molten metal refining furnace, solidification shrinkage becomes large, and it is difficult to obtain a refractory having a predetermined shape without problems.

Therefore, the present invention provides a furnace construction method as shown in FIG. That is, the molten metal refining furnace iron shell or permanent lining 2 lined on the iron shell 1 and the shape-retaining plate 3
This is a method in which an enclosure consisting of and is formed, the thermal spraying device 4 is arranged in parallel with the iron skin, and thermal spraying is performed while the movement of the shape retaining plate 3 is synchronized with the movement of the thermal spraying device 4 to perform a furnace construction. In this method, since the furnace is constructed by thermal spraying in the enclosure having a predetermined thickness, the amount of solidification shrinkage can be controlled, the occurrence of cracks can be suppressed, and the lining thickness can be controlled. Although the thickness of the lining depends on the size of the molten metal refining furnace, it is generally preferably about 100 mm to 150 mm. This is because if it is less than 100 mm, the width of the refractory sprayed layer obtained by one spraying is narrow and the time required for lining becomes long, and if it exceeds 150 mm, solidification shrinkage,
This is because it becomes difficult to control the thickness of the sprayed layer. As the material of the shape-retaining plate, heat-resistant steel, metal-based refractory materials such as Ni-based alloys, or ceramic-based heat-resistant materials mainly composed of metal oxides, metal carbides, metal nitrides, metal borides, etc. Material is preferred.

[0012]

EXAMPLES The present invention will be described below based on examples. However, the present invention is not limited to these examples. Example 1 A refractory lining for a RH lower tank was constructed with a refractory material composition according to the present invention and a refractory material composition outside the scope of the present invention, and their durability was compared. Table 1 shows the results.

[0013]

[Table 1]

The thermal spraying conditions are shown in Table 2.

[Table 2]

As shown in Table 1, according to the present invention, a lining refractory lining having superior durability and higher durability than the comparative example can be obtained.

Example 2 The RH lower tank lining refractory lining was constructed according to the present invention as shown in FIGS. 1 and 2 and the conventional method as shown in FIG. Variation in lining thickness,
And the time required for furnace construction was compared. Table 3 shows the results.

[0017]

[Table 3]

The thermal spraying conditions for both the present invention and the conventional method are shown in Table 2. As shown in Table 3, in the present invention, the durability of the lining refractory is better than that in the case of applying the divisional construction method which is a conventional method, and variations in the lining thickness,
Few. Furthermore, the time required for construction is short. 2 and 3
The numbers with a circle mark indicate the order of construction.

[0019]

Industrial Applicability According to the present invention, it has become possible to save labor and mechanize the work of constructing a refractory for a molten metal refining furnace, and at the same time, to obtain a refractory lining having a high durability. Therefore, the present invention is suitable for the construction of a molten metal refining furnace such as a ladle and a secondary refining furnace.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of the present invention.

FIG. 2 is an explanatory diagram of a furnace construction method according to an embodiment of the present invention.

FIG. 3 is an explanatory view of a furnace construction method in an example of a zone division construction method which is a conventional method.

[Explanation of symbols]

 1 Iron skin 2 Permanent lining 3 Shape retention plate 4 Thermal spraying device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Tamura 20-1 Shintomi, Futtsu-shi Inside the Technology Development Division, Nippon Steel Corporation (72) Inventor Shigemi Harada Oita-shi 1st Nishinosu Nippon Steel Co., Ltd. Company Oita Works

Claims (2)

[Claims] 1. A refractory powder 70 having a particle diameter of 300 μm or less which is completely melted in a flame having a flame temperature of 2300 ° C.
Molten metal refining furnace iron skin by a flame spraying method using a thermal spray material consisting of 10% by weight or more and 30% by weight or less of refractory powder having a particle diameter of 1 mm or more and 5 mm or less that melts only the surface in the flame. Alternatively, a furnace construction method characterized by forming a refractory lining by adhering it to a permanent lining lined with iron skin. 2. A portion to which a refractory is applied is surrounded by a molten metal refining furnace iron shell or a permanent lining lined with the iron shell and a shape retaining plate, and flame spraying is performed in a direction parallel to the molten metal refining furnace iron shell. The method for constructing a furnace is characterized in that the thermal spray material is adhered to the molten metal refining furnace iron shell or the permanent lining lined on the iron shell to form a refractory lining by carrying out.