JPH0748168A - Refractory for preliminarily treating molten pig-iron - Google Patents

Abstract

PURPOSE:To obtain a refractory for preliminarily treating molten pig-iron having excellent melting loss resistance and spalling resistance, standing use of an ultra-high temperature in the vicinity of a pig-iron receiving port close to an air or oxygen lance of a mixer car by blending a magnesia raw material or magnesia.calcia raw material (hereinafter abbreviated as magnesia raw material) with silicon carbide and a carbon material in a specific ratio. CONSTITUTION:60-95wt.% of magnesia raw material is blended with 3-30wt.% of silicon carbide and 2-30wt.% of a carbon material, kneaded and molded by a friction press, etc. The molded material is heat-treated at about 300 deg.C for about 10 hours to give an unburned refractory. For example, fused magnesia clinker is used as the magnesia raw material and magnesia clinker as the magnesia.calcia raw material. The carbon material contributes to corrosion resistance and spalling resistance by hardly wetting slag and, for example, both graphite and pitch are used. Silicon carbide has effects of suppressing oxidation of the carbon material, especially oxidation at an ultra-high temperature under exposure to an oxygen gas and exhibiting high corrosion resistance and high spalling resistance of the carbon material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot metal pretreatment refractory such as a hot metal wheel and a hot metal ladle capable of carrying out hot metal pretreatment such as desiliconization, dephosphorization and desulfurization at the same time when hot metal is transported. .

[0002]

2. Description of the Related Art Conventionally, low-rock or chamotte refractory has been used as a refractory for hot metal pretreatment containers such as a hot metal car and a hot metal ladle. Cars and hot metal ladles not only serve as containers for transporting blast furnaces and converters, but also serve as refining containers for performing hot metal pretreatment such as desiliconization and dephosphorization.
Since conventional refractory materials such as low-grade stones have a large amount of wear due to the rise in hot metal temperature and activated slag, alumina, silicon carbide, and carbonaceous refractories using sintered alumina or fused alumina raw materials are used. (For example, JP-A-58-8
4915 publication).

[0003]

This alumina / silicon carbide / carbonaceous refractory has high corrosion resistance,
In particular, when gas acid dephosphorization treatment comes to be performed, for example, the temperature near the pig iron port near the gas acid lance of a mixed piggy car reaches 1800 ° C, and damage to refractories due to melting and spalling increases,
Even with alumina, silicon carbide, and carbonaceous refractories, their durability is insufficient.

Attempts have also been made to apply the magnesia carbon bricks used in converters as a refractory material capable of withstanding melting damage and spalling damage at high temperatures for hot metal pretreatment. However, although magnesia carbon brick has a large spalling resistance, it cannot be used because it is heavily oxidized by oxygen gas, and a new refractory is desired.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have solved the above-mentioned inconveniences in refractory for hot metal pretreatment, and have spalling resistance and corrosion resistance as compared with conventional alumina / silicon carbide / carbonaceous refractory, As a refractory having excellent oxidation resistance, magnesia / silicon carbide / carbonaceous refractory and magcalcia / silicon carbide / carbonaceous refractory have been developed to complete the present invention. That is, the present invention uses 60 to 95% by weight of a magnesia raw material or a magnesia / calcia raw material, and 3 to 30 silicon carbide.
It is a refractory for hot metal pretreatment, which is composed of 2% by weight of carbon material and 2 to 30% by weight of carbon material.

As the magnesia refractory material used in the present invention, electromelted magnesia clinker, sintered magnesia clinker, natural magnesia clinker and the like are used alone or in combination. In the case of magnesia / calcia refractory material, the magcalcia clinker is used alone or as a mixture with the magnesia clinker. The magcalcia clinker may be a sintered or electromelting clinker having a CaO content of 1% by weight or more in the clinker.
It is more effective to use one having a CaO content of 1 to 10% by weight, moreover, CaO is distributed in pericles crystal grain boundaries and has a structure in which pericles crystal grains are connected by a CaO network cross-linking structure. Is. Further, it is possible to use these basic materials as a main component and also use a small amount of other oxide refractory materials, non-oxide refractory materials, and the like. The amount of magnesia refractory material or magnesia / calcia refractory material used is 60 to 95% by weight.

The carbon material contributes to corrosion resistance and spalling resistance because it is hard to get wet with slag, and it is used in combination with graphite such as natural graphite and artificial graphite or pitch and the like, and the amount thereof is 2 to 30% by weight. This amount is 2
If it is less than 30% by weight, the effect of the carbon material is not sufficiently exerted and the spalling resistance is lowered, and if it is more than 30% by weight, the strength and the corrosion resistance of the refractory are lowered.

Silicon carbide has an effect of suppressing the oxidation of the carbon material and exerting the high corrosion resistance and the high spalling resistance of the carbon material, and in particular, it is an object of the present invention that a pig iron port close to a gas acid lance of a pig iron car. It is suitable for bounce of slag and oxidation prevention of carbon material under the condition of being exposed to oxygen gas at an extremely high temperature in the vicinity.
The amount of silicon carbide used is 3 to 30% by weight. If this amount is less than 3% by weight, the antioxidant effect of the carbon material will not be sufficiently exerted, and if it exceeds 30% by weight, the strength and corrosion resistance of the brick will be reduced.

In addition to the above raw materials, metals such as aluminum, magnesium and silicon, and glass substances such as alloy powder and frit can be added, whereby the oxidation resistance is further improved. According to a conventional method, a binder is added to these raw materials, and the raw materials are kneaded, molded, and then heat-treated to be used as an unfired brick. As the binder, a resin-based binder is preferable, and a phenol resin that is cured by heat treatment is preferable. The heat treatment after molding is performed in the range of 200 to 800 ° C.

The refractory for hot metal pretreatment of the present invention has a smaller elution amount with respect to the dephosphorization treatment agent because magnesia is smaller than alumina because the treatment agent is mainly CaO. Has better corrosion resistance than refractory materials. When magnesia / calcia refractory material is used, the CaO component in FeO brick contained in the dephosphorization agent is easily eroded, but the magnesia / calcia refractory material has large pericles crystal grains, and the CaO component is present at the grain boundary. It does not matter if the existing form of magcalcia clinker is used. Further, the vitreous substance generated by the oxidation of silicon carbide contained at the same time has a function of coating the refractory material, and both the magnesia refractory material and the magnesia / calcia refractory material have high corrosion resistance to the dephosphorization treatment agent. Further, as to the desiliconization slag, although the elution amount of magnesia is smaller than that of alumina, though not so much as that of the dephosphorization treatment agent, the corrosion resistance is better than that of alumina / silicon carbide / carbonaceous refractory. Corrosion resistance to desiliconization slag is higher when magnesia-calcia refractory material is used than magnesia refractory material. Particularly, the magnesia / calcia refractory material has a great effect of preventing slag penetration because the CaO component in the material raises the viscosity of the slag against the slag penetration peculiar to the basic material. Furthermore, in combination with the slag penetration preventing effect of the CaO component, C existing in the pericles grain boundaries
Since the aO component has a creep characteristic, the spalling resistance becomes particularly good.

[0011]

EXAMPLES Table 1 shows formulations using magnesia materials (Examples 1 to 6), and Table 2 shows formulations using magnesia-calcia materials (Examples 7 to 12). Knead each compounded composition and mold with a friction press,
Heat treatment was carried out at 0 ° C for 10 hours to obtain an unfired refractory material. Physical properties of the refractory after heat treatment and various test results are shown in the same table. Further, as comparative examples, the cases of alumina / silicon carbide / carbonaceous refractory (Comparative Example 1) and magnesia / carbonaceous refractory (Comparative Example 2) are shown in Table 1.

Corrosion resistance is 1600 ° C according to the rotary slag test method
I went there for 2 hours. The composition of the desiliconization slag is 46% by weight of CaO, 46% by weight of SiO ₂ , 4% by weight of FeO and 4% by weight of MnO, and the composition of the dephosphorization treatment is 46% by weight of CaO and Fe.
O 46 wt% and CaF ₂ 12 wt% were used respectively. Both of the results are represented by a melt loss index with Comparative Example 1 of Table 1 being 100.

In the oxidation resistance test, the reciprocal of the decarburized area of the sample heated in air at 1600 ° C. for 2 hours was expressed as an index with the comparative example being 100.

In the spalling resistance test, the elastic modulus maintenance ratio before and after the operation of dipping in 1500 ° C. hot metal, pulling it up, and cooling to room temperature was repeated three times was also expressed by an index with Comparative Example being 100.

[0015]

[Table 1]

[0016]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the magnesia / silicon carbide / carbonaceous refractories of the present invention (Examples 1 to 6) and the magcalcia / silicon carbide / carbonaceous refractories (Examples 7 to 7). 12) is the corrosion resistance to desiliconization slag and dephosphorization treatment agent is alumina / silicon carbide / carbonaceous refractories (Comparative Example 1)
Compared with magnesia / carbonaceous refractories (Comparative Example 2), magnesia / silicon carbide / carbonaceous refractories are slightly less than those of magnesia / silicon carbide / carbonaceous refractories. Is equivalent. However, it is far superior to magnesia-carbon refractory in terms of oxidation resistance and is superior in spalling resistance. Furthermore, all of the refractory materials of the present invention have a performance that does not exceed that of alumina, silicon carbide, and carbonaceous refractory materials in terms of oxidation resistance, and it is understood that the refractory materials of the present invention are superior overall.

[0018]

As described above, the present invention uses magnesia / silicon carbide / carbonaceous refractory in place of magnesia / silicon carbide / carbonaceous or magcalcia / silicon carbide / carbonaceous refractory. Corrosion resistance and spalling resistance that carbonaceous refractories do not reach are obtained, and it has sufficient durability when used in the hot metal pretreatment container, especially in the vicinity of the pig iron port near the vapor acid lance of the mixed pig car. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirokuni Takahashi 1799-1 Ibe, Bizen City, Okayama Prefecture (72) Inventor Kazuo Nonobe 7 at 1099 Ura-Ibe, Bizen City, Okayama Prefecture (72) Inventor Satoshi Hayashi, Kibitsu 591, Okayama City Address 2

Claims (2)

[Claims] 1. A refractory for hot metal pretreatment, which comprises 60 to 95% by weight of a magnesia raw material, 3 to 30% by weight of silicon carbide, and 2 to 30% by weight of a carbon material. 2. A refractory for hot metal pretreatment, which comprises 60 to 95% by weight of magnesia / calcia raw material, 3 to 30% by weight of silicon carbide, and 2 to 30% by weight of carbon material.