JPS6049156B2 - Fireproof castable for ladle lining - Google Patents

Description

Detailed Description of the Invention The present invention is used for lining a container generally called a ladle, which accommodates high-temperature molten metal such as hot metal or molten steel for transfer or reaction treatment. The purpose of the present invention is to provide a refractory castable that has high corrosion resistance against slag, molten steel, etc., and is excellent in heat-resistant spalling during thermal cycles of heating and cooling.

In recent years, refractory lining materials for ladle are made by adding additives such as binder, deflocculant, flocculant, curing agent, drying accelerator, etc. to monolithic refractory material and 6 to 8% water and kneading the mixture. The number of refractory castables constructed by pouring has increased, and various types of refractory castables have been developed and used.

The advantages of pouring construction using these fireproof castables are:
These include labor savings through mechanization of construction, improvement of the working environment, and the ability to easily perform partial overlay repairs.

Refractory castable for ladle lining generally uses silicic acid, mono-zircon silicate, zircon, etc. as the main raw materials, and hydraulic castable refractories that use alumina cement as their binding material, clay, There are clay bonded castable refractories that use finely powdered refractory clay such as kaolin.

In the former type of hydraulic castable, alumina cement, which is a binder, is usually added in w weight percent or more;
When used, it not only has poor hot properties in the high temperature range of 1200°C or higher, but also has the disadvantage of significant deterioration of strength due to dehydration in the intermediate temperature range of 800 to 1000'C. In the case of castable for ladle whose main component is AI2O.

The melting temperature is significantly lowered by an excessive amount of , making it unsuitable for this type of application. The latter clay-bonded castable refractory contains calcium aluminate and calcium hydroxide as flocculants J, and Al derived from siliceous raw materials such as zircon and fireclay as main raw materials.

O, and CaO produce a low-melting material in the refractory castable for ladle, which is mainly composed of silicic acid, which reduces the resistance to erosion and loss.Also, the sinterability of the heat-receiving surface increases, so it cannot be heated for a long period of time. - Repeated thermal cycles of cooling often cause peeling damage, reducing the service life of the ladle. This invention solves the above-mentioned drawbacks in a refractory castable for ladle lining that is mainly composed of silica. The total content of alumina (AI2O3) is 5.0~
A refractory castable for lining a ladle, characterized in that the content is 1J% by weight.

The component structure of this invention will be explained below. The siliceous raw materials used in this invention are silica sand, silica stone, amorphous silica, and have a particle size of 6. - The following aggregates. The main component of zircon (ZrsiO4) is fine powder of 0.3Tf0n or less, but those with a maximum particle size of 6.0wn or less are used for high zircon quality. The alumina cement is a commercially available product, such as Alcoa CA-2\Denka Hi-Alumina Super, Sekar 250, and Type 1 and Type 2 alumina cement defined by JISR 25ll. The ratio of alumina cement added in this invention is 0.5 to 2.0 per 100 parts of the refractory aggregate! Weight percent is preferred. This is to reduce the alumina content of the entire castable refractory as will be described later, and if it is less than 0.5% by weight, the curing time after construction of the refractory castable will be prolonged, causing trouble in ladle operation. Also, if 2.0% by weight or more is added, CaO3
and Al2O3 increase, the refractory castable tends to have a low melting property, and oversintering occurs in a high temperature range, which is undesirable. Now, the most important *8 points of this invention, which has silicic acid as its main component, are that alumina (Al2O3
) content is 5.0 to 1. It is to mix so that the amount is %. FIG. 1 shows the influence of the content of alumina (Al2O3) in a silicate-zircon castable refractory on the melting temperature.

That is, Al. It can be seen that the melting temperature of the castable refractory decreases significantly as the O3 content increases. A decrease in the melting temperature increases the melting loss of the ladle during use, and also causes cracking and peeling due to sintering shrinkage. The melting temperature was determined according to JISR22O4, and the temperature at which the tip of the test cone contacted the pedestal was measured.
Next, regarding the alumina content, the lower limit is 1.00, taking into account the minimum required amount of alumina cement in the mix and Al2O3 contained in fireproof aggregate, etc. Call volume % is required, and 5. If the amount of saliva exceeds %, the melting temperature for a refractory for ladle lining cannot be ensured, so the upper limit was set at 5 J weight %.

The fire-resistant castable of this invention contains sodium phosphate and sodium amate as deflocculants to increase fluidity during construction, calcium hydroxide as a curing accelerator for alumina cement, or metal as a drying accelerator. Adding small amounts of aluminum etc. improves workability.
It is also effective for accelerating curing and drying.

Table 1 shows the formulations of examples of the present invention and conventional fireclay bonded castables, their chemical components, physical properties, and practical results in ladle.

Table 2 is a chemical analysis table of the raw materials used for each of these fire-resistant castables. Example 1 is Zircon 7
Although it is a silica-zircon refractory castable with a silica content of 1.0% by weight, the amount of alumina cement added is 1.0% by weight, and the Al2O3 content of the entire refractory castable is 1.0% by weight. It has a melting temperature of 1,780°C, which is less than 1/3 of that of conventional fireclay bonded castables, and its melting temperature is as high as 1,780°C, and as judged from the various physical properties after heating, it is extremely sinterable compared to conventional fireclay castables. It is a castable material that is difficult to tie.

As a result of actual use in a 250t molten copper ladle, there was almost no cracking or peeling, and the service life was 100 charges, about twice that of conventional castable castables.

Example 2 is a silica-zircon refractory castable with a zircon content of 7%, and the amount of fireclay added is three times that of Example 1, and the amount of alumina cement added is 1. As a result, the total content of Al2O3 was 2.9% by weight, but the melting temperature decreased by 20°C, and the sinterability increased slightly in terms of physical properties, but the corrosion resistance was also reduced when actually used in a molten steel ladle. The results were good, with an average number of uses of 65 charges.

Example 3 is a doxite-zircon refractory castable with mwt% zircon, Al2O3 from doxite aggregate and alumina cement 1. Total Al2 by addition of nominal amount %
Although the O3 content has increased to 3.8%, the corrosion resistance and degree of cracking and peeling are better than that of conventional waxite-zircon clay bonded castables as a result of use in 25-Iru steel ladle. It was hot.

However, cracks and peeling were observed in some parts, and the average service life was 62.
Although it had a shorter lifespan than the charge and Example 1, it was sufficiently useful for practical use.As detailed above, the melting temperature of refractory castable whose main component is silicic acid is the same as corrosion resistance, cracking and peeling, and eventually removal. Effect on the service life of the pot,
Based on the knowledge of the correlation between melting temperature and AI2O3 content, by limiting the total alumina content in refractory castables, we can achieve longer lifespan than conventional fireclay-bonded refractory castables. It was possible to obtain a refractory castable for ladle lining that has a service life that is almost twice as long.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a diagram showing the relationship between the alumina content of refractory castable and the melting temperature of refractory castable.

Claims (1)

[Claims] 1. In refractory castable in which alumina cement is added to refractory aggregate made of siliceous raw materials and zircon, the total content of alumina (Al_2O_3) is 5.0 to 1.0.
Fireproof castable for ladle lining, characterized by weight%.