JPH07126734A - Slag cut ball - Google Patents

Abstract

PURPOSE:To improve a slag cut effect by prevention of failure at the time of use and an increase in bulk sp. gr. by limiting the content of the alumina cement of castable refractories for covering the outside surfaces of arbors. CONSTITUTION:The balls are constituted by limiting the content ratio of the alumina cement in the sheath refractories to 1 to 9wt.%. As a result, the water of crystallization contained in the refractories is made less than in the conventional refractories and the bulk sp. gr. of the balls is increased. Then, the balls are held in a sunk state without generating the crack and destruction by a rapid temp. change when the balls are charged into the furnace and, therefore, a slag cut rate is improved. The degradation in the hardening strength by a reduction in the content ratio of the alumina cement is sufficiently dealt with addition of 0.1 to 5wt.% superfine powder of silica and 0.01 to 1wt.% dispersant, such as phosphate, carboxylate or silicate of alkaline metals to the refractories.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a slag for preventing molten slag from flowing into a ladle when the molten steel is discharged from a tapping port of a metal refining furnace such as a converter. The present invention relates to a slag cut ball having a specific gravity approximately in the middle of molten steel.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view of an example of the shape of a slag cut ball, FIG. 4 is an explanatory view of the use of a slag cut ball 1 in a converter, and (a) is an explanatory view at the time of discharging molten steel 2. b) is an explanatory view of a state in which the slag 3 is prevented from flowing out to the ladle 6 after discharging the molten steel.

Conventionally, in this type of slag cut ball, there has been used a slag cut ball composed of a core metal and castable refractory material whose specific gravity is adjusted so as to be heavier than slag and lighter than molten steel. As an example of related prior arts, JP-A-1-263215 and JP-A-2-175812.
There is a gazette.

[0004]

However, the castable refractories conventionally used are required to have high strength in view of handling strength and resistance to wear by molten steel flow, and the content of the alumina cement as a binder is required. Usually, a large amount of 12 to 30% by weight was required. Therefore, the amount of kneading water increased, and the water content (free water, crystallization water) after molding and curing was large.

[0005] This often causes boiling, cracking, explosion, etc. in the molten steel at the time of rapid dehydration when it is put into the furnace, and often fails to perform slag cutting well. This is due to the behavior of the hydrated alumina cement in the castable refractory, that is, it is considered that dehydration reaction as shown in Table 1 occurs during the drying process of the hydrated alumina cement in the castable. Thus, it can be seen that there is a large amount of water of crystallization.

[0006]

[Table 1]

[0007]

In view of the above, the present invention focuses on this water content and aims to reduce the amount of alumina cement in the castable refractory composition. The content of alumina cement is set to 1 to 9% by weight. It was done. Of course, only reducing the amount of alumina cement causes a decrease in strength, so ultrafine silica powder, a dispersant, etc. are used together.

[0008] For example, the Japanese Patent Publication Sho 6 previously proposed by the applicant.
No. 1-38154 "A fire-resistant aggregate with a particle size adjusted, a hydraulic cement of 0.5 to 10% by weight, and a particle size of 2
Hydrosetting fire resistance consisting of 0.1-10% by weight of siliceous powder having a specific surface area of 0 m or less and a specific surface area of 10 m ² / g or more, 0.1-3% by weight of metallic aluminum and 0.01-1% by weight of a dispersant. Composition. Is preferred.

Alumina cement is JIS type 1, type 2, 3
Species, Species 4 and high alumina cement can be used, and the amount used is 1 to 9% by weight. If it is less than 1% by weight, sufficient strength cannot be obtained, and if it exceeds 9% by weight, the water content is increased, which causes a momentary setting with the dispersant and loses fluidity.

As the ultrafine silica powder, white carbon, anhydrous, hydrous amorphous silicic acid, and evaporated silica can be used, and the particle size is several millimicrons to several tens of millimicrons as primary particles, and secondary particles formed by agglomeration of these particles are also available. 20μ or less, the specific surface area is 10
It reaches m ² / g or more. The amount used is preferably 0.1 to 6% by weight.

As the dispersant, alkali metal phosphates, alkali metal carboxylates, alkali metal silicates and the like can be used, and the amount used is preferably 0.01 to 1% by weight. Further addition of aluminum metal powder contributes to strength development due to hydration exothermic reaction. The amount used is preferably 0.05 to 2% by weight.

[0012]

[Operation] If slag-cut balls cast from castable refractory are treated (calcined) at a temperature high enough to eliminate crystal water, the water content will decrease and the problem will be solved, but the cost will increase, and If the cured product has a water content, dehydration causes an increase in porosity, deterioration in strength, and deterioration in corrosion resistance.

In the present invention, in order to solve these problems,
The aim is to reduce the amount of water from the initial starting point as well as to reduce the water of crystallization due to the formation of hydration reaction. Fig. 1 compares the characteristics of the castable refractory product of the present invention product and the conventional product. Fig. 1 (a) shows the relationship between the amount of alumina cement (expressed in terms of CaO) and strength. 1 (b) is a diagram showing required water amount characteristics, and FIG. 1 (c) is a diagram showing strength characteristics. The product of the present invention has high strength and exhibits excellent properties despite the small amount of alumina cement.

[0014]

[Examples] The formulations of Examples and Comparative Examples are shown in Table 2.

[0015]

[Table 2] Composition (% by weight)

Nine slag-cut balls of Comparative Example and three slag-cut balls of Example 1 were cast and deframed, and heat-dried at the temperature shown in FIG. 2 to measure the weight immediately after deframing and the weight after drying. The weight of the castable portion is shown in Table 3. The weight of each core is 54 kg. The amount of water added during kneading was 14% in the comparative example and 7.0% in the example.

[0017]

[Table 3]

The castable refractories of Examples 1, 2 and 3 and the comparative example are respectively 250 mm × 250 mm × 100 mm.
Casting (dummy sample) in the rectangular form of
It was dried and further fired in an electric furnace at 500 ° C. for 3 hours.
The change in weight at that time is shown in Table 4. The drying was performed at the temperature shown in FIG.

[0019]

[Table 4]

The same dummy sample as described in Table 4 was dried to the temperature described in FIG. 2 and then rapidly heated to 1600 ° C. Although cracks occurred in the comparative example, no abnormality occurred in the dummy samples of Examples 1, 2, 3, and 3. Further, the slag-cut balls of Comparative Example (after drying) and the slag-cut balls of Example 1 (after drying) described in Table 3 were added into the converter. Although cracks occurred in the comparative example, no abnormality occurred in the slag cut ball of Example 1.

As shown in the above data, it can be seen that the product of the present invention has a small amount of added water, a high dehydration rate, and is free from cracks and the like even when it is rapidly heated.

[0022]

EFFECTS OF THE INVENTION The slag cut ball of the present invention can prevent boiling, cracking and the like by reducing the water content.

The slag-cut balls of the present invention have an increased bulk specific gravity (conventional products 4.1 to 4.5, and the products of the present invention are 4.6 to 4.9). It was held with the head of the ball thrust deeply into it, which improved sinking and contributed to the improvement of the slag cut rate.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing characteristics of the product of the present invention and a conventional product.

FIG. 2 is a diagram of a drying temperature in an example.

FIG. 3 is a perspective view of a slag cut ball.

FIG. 4 is an explanatory diagram of use of a slag cut ball in a converter.

[Explanation of symbols]

1: Slag cut ball, 2: Molten steel, 3: Molten slag, 4: Converter, 5: Steel tap, 6: Ladle, 7: Castable refractory, 8: Lifting tool, 9: Groove.

Front page continuation (72) Hiroto Amaha, Hiroto Amaha 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Works Co., Ltd. Service Center Kurosaki Kiln Co., Ltd. Kimitsu Branch Office (72) Inventor Tomomi Yamaguchi Kimitsu, Kimitsu, Chiba Prefecture No. 1 Nippon Steel Co., Ltd. Kimitsu Works Co., Ltd. (72) Inventor Shigeo Iwama No. 1 Kimitsu, Kimitsu City, Chiba Prefecture Nippon Steel Co., Ltd. Kimitsu Co., Ltd. (72) Inventor Kiyoshi Takahashi No. 1 Kimitsu, Kimitsu City, Chiba Prefecture Kimitsu Works, Nippon Steel Co., Ltd.

Claims (1)

[Claims] 1. A slag cut ball having an outer surface of a core metal coated with a castable refractory material, wherein the castable refractory material has an alumina cement content of 1 to 9% by weight.