JPH04144957A - Production of magnesia with erosion resistance to slag - Google Patents

Abstract

PURPOSE:To obtain the title magnesia useful as a thermal insulating material in the ladles and tundishes in iron and steel production by sufficiently sintering a magnesia granulated product. CONSTITUTION:A magnesia granulated product is calcined by heating it to its sintering initiation temperature. For sufficient sintering, considerably high temperature will be required depending on its physical properties. In the case where such a high temperature is difficult to be realized from a physical or economical point of view, the surface of the granulated product is coated with fused magnesia powder having physical properties similar to those of the granulated product followed by calcining; thus, the purpose can be virtually attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing slag-resistant magnesia, which is used as a heat insulating material in ladles and tundishes in steel manufacturing processes.

[Conventional technology]

Conventionally, burnt rice husks and magnesia granules have been widely used as heat insulating materials and surface coating materials for molten metal in ladles and tundishes.

[Problem to be solved by the invention]

However, if high-purity mesh is required, burned rice husks contain large amounts of silica and carbon blank, which are considered impurities in steel, and are becoming increasingly difficult to obtain due to factors such as reduced rice acreage. There is.

In addition, when conventional surface coating materials made of magnesia granules enter into high-temperature molten metal, small particles of magnesia are liberated, and when they come into contact with molten slag, they react with silica, manganese, etc. in the slag to form a solid solution. However, there is a problem that the shape of magnesia granules cannot be maintained, and as a result, the generated solid solution increases the amount of slag and remains attached to the walls of ladle and tundish, injection nozzle, etc. in the steel manufacturing process. This caused operational problems.

The present invention prevents slag from being released into the molten metal in the ladle and tundish during the steel manufacturing process, and is non-corrosive to slag, thereby preventing an increase in the amount of slag and preventing the insulating bricks of the ladle from becoming loose. The object of the present invention is to provide a method for producing slag-erosion resistant magnesia that can keep molten metal warm without damaging it.

[Means to solve the problem]

According to the present invention, the above object is achieved by: heating and firing the magnesia granules to a sintering generation temperature.

[Effect]

In the magnesia sintered product according to the present invention, the gaps between the particles are reduced due to sintering of the magnesia granules, and the contact area with the slag is extremely reduced. As a result, the corrosive effect of slag is suppressed.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings and in comparison with conventional examples.

In this example, magnesia granules having the main composition shown in Table 1 were heated to 30 to 60% at a high temperature of 1400°C or higher, which is the firing temperature.
A magnesia fired product obtained by firing for a minute was used as a prototype.

Table 1 Main material composition of prototype magnesia (Igloss: 3.1%) Thus, Obtained prototype 6 g is shown in Table 2. Put it in 20g of slag mainly composed of the same substance and heat it at 1600℃. The results were examined by contacting them in an atmosphere.

Table 2 Main substance composition of slag On the other hand, in order to compare with the above prototype, magnesia granules obtained by a conventional method were used as a comparative product, and 6 g of the comparative product was
Place it in 20g of slag similar to the above prototype, and
The results were examined by contacting them in an atmosphere of 600°C.

Conventional magnesia granules (comparative product) were eroded by contact with molten metal and slag and reacted, resulting in the magnesia granules losing their shape. An investigation of the corrosion phenomenon shows that it progresses at the interface (contact surface) between magnesia and slag, and the erosion rate tends to increase depending on the surface area of the interface. When this was observed with a metallurgical microscope, it was observed that some sintering remained in the form of granules, as shown in Figure 4, but due to the large number of gaps between the particles and the large contact area with the slag, the sintering was short-lived. eroded by time.

Next, in the magnesia sintered product (prototype) in this example, magnesia granules are sintered, so as shown in Figure 1, it is different from the conventional magnesia sintered surface coating material. In comparison, high-temperature sintering causes large sintering growth, fewer interparticle gaps, and a decrease in surface area.

By advancing sintering through sufficient sintering in this way, it was possible to prevent corrosion reactions on the surface, and the insulation material was able to maintain its shape even when in contact with molten metal and slag for a long time. .

However, in order to proceed with more sufficient sintering, a considerably high temperature is required depending on the physical properties of magnesia. If this is physically or economically difficult, similar results can be obtained by coating the surface of the magnesia granules with electrofused magnesia powder having similar physical properties and firing.

A more detailed discussion will be made regarding the comparison with the prototype and comparison holes as described above.

Figures 2 and 5 show the surface appearance of the prototype in contact with the slag and the comparison hole taken out into the container, respectively.

The prototype (Figure 2) retains its granular shape even though it is in contact with slag, but the comparison hole (Figure 5) shows that the original shape of the granules is due to the reaction between magnesia and slag. is lost, forming a solid solution. This also shows that the magnesia sintered product according to the present invention has excellent slag reactivity resistance.

Next, the cross sections of the prototype after contact with the slag and the inside of the comparison hole were observed using a metallurgical microscope and an EPMA, and as a result, the results were obtained as shown in FIGS. 3 and 6, respectively. As shown in Figure 3, in the prototype, a small amount of slag was observed between the magnesia particles, but the magnesia sintered material maintained its granularity almost completely, indicating that the silica in the slag and the magnesia sintered material had reacted. However, it is not possible to confirm the solid solution formed.

Furthermore, in the comparison hole shown in FIG. 6, most of the magnesia particles react with silica in the slag, causing
A chemical change occurs at f04, and the magnesia granules are eroded by the slag, producing a square solid solution.

From these results, it was confirmed that the magnesia sintered product of the present invention has excellent slag corrosion resistance.

〔Effect of the invention〕

As revealed from the above results, the magnesia sintered product according to the present invention has a durable lag corrosion property not found in conventional products, and when used as a surface coating material for molten metal, there is no increase in slag. When used as a heat insulating material for ladles, etc., the ladle can be used for a longer period of time because there is less damage to the heat insulating material due to erosion.

[Brief explanation of the drawing]

FIG. 1 is a microscopic photograph showing the surface of a prototype as an example of the present invention after it has come into contact with slag, and FIG. 2 is a photograph showing the surface of the prototype when it is taken out into a container together with slag.
Figure 3 is a microscopic photo of the cross-section of the prototype with slag after solidification, Figure 4 is a microscopic photo showing the surface of the comparison hole of a conventional product after contact with slag, and Figure 5 is a photomicrograph showing the surface of the comparison hole as a conventional product after contact with slag. FIG. 6 is a photomicrograph showing the surface of the slag taken out into the container, and FIG. 6 is a microscopic photo of the cross section of the comparison hole together with the slag after solidification. Patent Applicant Kunikofu Lime Industry Co., Ltd. Figure 1 Figure 2 Procedural Authorization (Method) January 30, 1991

Claims (2)

[Claims] (1) A method for producing slag corrosion-resistant magnesia, which comprises heating magnesia granules to a sintering temperature and firing them. (2) The method for producing slag erosion-resistant magnesia according to claim (1), wherein the magnesia granules are coated with electrofused magnesia powder and then fired.