JPS62290820A - Molded body for blowing gas - Google Patents

Abstract

PURPOSE:To obtain a molded body for blowing gas having superior spalling resistance and undergoing no deterioration in the corrosion resistance even after repeated use by adding specified amounts of carbon powder and a binder to a magnesian refractory and/or a spinel-base refractory. CONSTITUTION:The composition of a molded body for blowing gas is composed of 4-50wt% carbon powder, <20wt% binder and the balance magnesian refractory and/or spinel-base refractory. Pitch, phenol resin or other substance which remains in the form of carbon after heating is used as the binder The binder makes the molded body microprous.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention The present invention relates to a molded article for blowing gas into molten metal.

In recent years, in order to improve the quality of steel, gas is blown into molten metal through, for example, a porous plug to perform desulfurization or degassing and separation of nonmetallic inclusions.

The porous plug is subject to erosion and wear due to the stirring molten metal flow, and when the ladle is empty, the wear and tear is significant due to spalling due to cooling.

Therefore, various attempts have been made to improve the material and structure of molded bodies for gas injection, such as porous plugs.

It is desirable for the molded body to have a uniform pore size, no sintered layer during use, and high hot strength, but currently corundum, mullite, and basic materials are often used. ing. However, these materials tend to form a sintered layer, and molten steel penetrates from the surface of use, making uniform pubbling impossible. The degree of progress is not constant due to the progress of oxidation and shrinkage, resulting in pore blockage, pore formation, uneven distribution (and decrease in porosity), and changes in operating surfaces (when used multiple times). , gas injection cannot be performed uniformly throughout the entire operation, nor can it be performed at a fixed position. In addition, it could not be said to be satisfactory as it was easy to cause structural spalling.

The gas-blown molded article of the present invention corrects this drawback and is made of a fire-resistant material containing 4 to 50% by weight of carbon powder, 20% by weight or less of a binder, and the remainder being magnesia, spinel, or a combination thereof. characterized by something.

By adding 4 to 50 weight percent of carbon powder, volatile matter is removed from the binder and turned into coke, thereby creating fine pores. This helps prevent sintering during use and maintains uniform micropores. Furthermore, it reduces wetting with molten steel, prevents metal insertion, and increases corrosion resistance and spalling resistance. This was confirmed by measuring the pore size distribution, and it was also determined that the spalling resistance and corrosion resistance did not deteriorate significantly even if the number of service cycles increased.

When the amount of carbon powder is less than 4% by weight, a sintered layer is likely to be formed, and the wetting to molten steel becomes large, corrosion resistance is poor, and fine pore formation and uniform maintenance of fine pores during use cannot be achieved.

When the amount of carbon powder exceeds 50% by weight, oxidation resistance and strength are extremely reduced. In addition, due to the difficulty of sintering,
This has the effect that the joints can be cleaned easily when replacing the plug, the plug can be easily removed, and there is less damage. In addition, since there is no bare metal plug and it contains carbonaceous material, oxygen cleaning of the plug after multiple uses can be done effectively in a short time.

In addition, it is better to add oxidation resistance by adding rubber, silicon carbide powder, silica powder, etc., which need to provide oxidation resistance, but this has a slightly lower strength than in the case of 81 above. Inferior.

Further, the content of these silicon carbide powders and silica powders is 10% by weight or less, preferably 5% by weight or less.

The magnesia refractory material preferably has a content of 70 to 95% by weight;
If it is less than 0% by weight, the characteristics of the fireproof aggregate cannot be fully utilized,
Corrosion resistance and wear resistance are lost. If it exceeds 95% by weight, the properties will be too biased towards only the refractory aggregate, the spalling resistance will decrease, and it will be easy to sinter during use, making it impossible to maintain uniform fine pores.

The binder is pitch.

Fine pore formation is promoted by using phenol resin and other resins that remain in the form of carbon when heated. In other words, volatile matter is removed from the binder and the binder is turned into coke, thereby creating fine pores and carbon bonding, thereby imparting strength.The appropriate amount is less than 20% by weight, and if it exceeds 1% by weight, the strength is insufficient. .

The refractory aggregate is appropriately selected from known magnesia materials, but from the viewpoint of corrosion resistance and abrasion resistance, it is preferable to use one with as high a purity as possible, preferably 95% by weight or more of Mg.

The spinel may be of theoretical value, magnesia rich, or alumina rich.

Sintered alumina, fused alumina, mullite, bauxite, etc. are used as the alumina to be mixed in these, and the sintered alumina is preferably 95% by weight or more of Al2O3.

Moreover, the molded article for gas blowing of the present invention contains silicon.

The oxidation resistance and strength of the molded product can be increased by adding aluminum, magnesium, carunium, etc. alone, a mixture thereof, or an alloy thereof.

The molded body for gas blowing is commonly used in the form of a plug, but it can also be molded into a suitable shape such as a sliding plate brick for gas blowing, a nozzle brick, etc.

In addition, in the case of a sliding plate brick, the sliding properties are also improved, making it preferable.

Examples will be described below.

The first example has a particle size distribution of 2 to 1 mm diameter and 1 to 0.2 mm diameter.
.

Mg[] Using 99% by weight magnesia clinker,
This was mixed with 4% by weight of coal pitch as a binder. First, magnesia clinker is placed in a heating mixer and heated and mixed at 190° C. for 30 minutes, pitch is added, and the mixture is heated and kneaded for 15 minutes.

Next, after adding 5% by weight of carbon black and kneading with heat for 10 minutes, the clay obtained by cooling and sizing the crushed pieces was molded using an oil press at a molding pressure of 700 kg/c, with an upper surface of 58 φ and a lower surface of 104 φ. A truncated conical porous plug base brick with a height of 220 cm was obtained. Thereafter, the raw brick was reduced and fired at 1500°C to obtain a carbonaceous porous plug.

In addition, in the case of firing, it is fired at a temperature of 1200 to 1500°C, and in the case of non-firing, it is heat treated at a temperature of 150 to 200°C. The molding pressure is selected between 400 and 700 kg/cd. As a result, the apparent specific gravity is 3.54.
Bulk specific gravity 2.59. A material with an apparent porosity of 27.1% and a compressive strength of 175 kg/cm2 was obtained.

Second example Mg098 1% by weight magnesia linker and AR2D
Spinel linker with Y67 Shigesato and Mg027% by weight
The raw material for the clay was prepared using the following method.

First, both magnesia clinker and spinel clinker are placed in a heating mixer, heated and mixed at 190° C. for 30 minutes, pitch is added, and heated and kneaded for 15 minutes. Next, metallic silicon and carbon black were added, heated and kneaded for 10 minutes, then allowed to cool, and the resulting clay was crushed and sized to obtain a frustoconical porous plug base brick using an oil press at a molding pressure of 700 kg/c111. .

Claims (1)

[Scope of Claims] 1. A molded article for gas injection, which is a refractory material containing 4 to 50% by weight of carbon powder, 20% by weight or less of a binder, and the remainder consisting of magnesia, spinel, or a combination thereof. 2. The molded article for gas blowing according to claim 1, wherein the binder remains in the form of carbon when heated.