JPS5918174A - Lining material for molten metal treating vessel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides corrosion resistance to slag, pig iron, and steel containing soda ash, and spalling resistance to thermal changes. It has excellent properties and oxidation resistance at high temperatures, and also has NI
L20. 20 By lining the molten metal processing container with a refractory whose volume is stable against alkali vapor, wear and tear of the refractory is suppressed, the stability of the container is increased when the container is used, and the life of the container is increased. This invention relates to a lining material for an extended molten metal processing container.

Conventional molten metal processing vessels have primarily used alumina-siliceous materials. However, the service life is short due to erosion due to slag and thermal spalling. Furthermore, high alumina, magnesia, magnesia, and dolomite materials have high thermal expansion properties and are prone to spalling due to the penetration of slag and molten metal into their structures, making them difficult to put into practical use. In addition, in the presence of oxygen, the carbon of magnesia carbide oxidizes and dissipates as a gas. During use, a decarburized layer is formed near the operating surface, weakening the effect of preventing slag penetration. In the case of gold steel, it easily peels off from the decarburized part, making it impossible to obtain a long life. In addition, in the case of alumina-silicon carbide-carbon material, if there is a possibility that Na2O/K20 vapor may be generated, there is a risk that the alumina of the aggregate will react with Na2O/K2O and produce β-alumina, causing expansion and collapse. be.

The present invention aims to improve the drawbacks of such refractories and provide a lining structure for molten metal processing vessels that enables stable operation. The material is 3 to 30% by weight of carbides and/or nitrides, and 30 to 94% by weight of β-alumina.

The lining material of the present invention is, for example, soda ash hCaO,.F
The slag synthesized by adding eO and CAF2 is used to line the molten metal processing vessel, which prevents carbides and nitrides from oxidizing at high temperatures and dissipating carbon, resulting in good oxidation resistance. In the presence of alkali vapor, β-alumina has high stability, and due to carbon, it does not erode against slag and molten metal, and has a stable and long lifespan without being eroded even when used in molten metal processing containers. , and greatly improves the overall operating rate of the processing vessel.

Hereinafter, the limits for using β-alumina in each constituent condition of the lining material of the present invention are as follows: β-alumina is corundum, A
This is because, compared to T203-8102, it is stabilized at 20% by Na2O and does not react with Na2O+K2O to swell, collapse, or produce low melting point products.

The reason why β-alumina gin is limited to 30 to 94% by weight is 3
This is because if it is less than 0% by weight, the content of other components will be large and the oak, oxidation resistance, and corrosion resistance will be poor, and if it exceeds 94% by weight, it will be unfavorable for corrosion resistance against slag components other than soda and spalling resistance.

Carbides and nitrides combine with oxygen at high temperatures. For example, silicon carbide and silicon nitride oxidize to form 5102, boron carbide and boron nitride oxidize to form B2O3, and titanium carbide and titanium nitride oxidize. This reacts with NJL20/K2O in β-alumina to form a viscous oxide film on the brick surface, which prevents oxygen from entering the brick and removes the carbon in the brick. This prevents the oxidation of 3 to 3 carbides and/or nitrides
The reason why it is limited to 30% by weight is that if it is less than 3% by weight, the antioxidant effect cannot be obtained as shown in Figure 1 (Retention 1500℃ x 2 hours), and if it exceeds 30% by weight, the
2Hrs slag: CaO: 4, FeO: 4, Ca
F'z: 1, Na,, Co3: 1.8102:1
), it is not preferable because the corrosion resistance against slag and molten metal decreases.

The reason why carbon material is added is because β-alumina reacts easily with CaO and CaF2 r FsO, which are slag components other than soda ash, and is easily eroded. On the other hand, the material is stable in volume and resistant to erosion.

Furthermore, the spall resistance can be improved by adding the carbon material. Carbon content is 3-40% by weight, preferably 5-30% by weight
It is. The reason for limiting this range is that if the weight is less than 3, it will not easily get wet with slag, and as shown in Figure 2, the melting loss will be negligible.
In addition, this is because the spalling resistance decreases. If it exceeds 30% by weight, the strength decreases and the oxidation resistance decreases as shown in FIG.

As mentioned above, a molten metal processing vessel lined with β-alumina carbide/nitride carbonaceous refractory has excellent corrosion resistance against synthetic slag containing soda ash and a small volume against Na2O vapor. It is stable, has excellent oxidation resistance and spalling resistance, and has a long life.

In the present invention, among the β-alumina raw materials, other oxides and double oxides may also be used in combination depending on the purpose.

That is, magnesia and zirconia can be used in combination in areas where high corrosion resistance is required, and mullite, zircon, fused silica, and corundum can be used in combination when there is no soda vapor or the amount generated is extremely small.

Furthermore, if necessary, metal silicon and/or metal aluminum may be added to the refractory of the present invention to combine with carbon in the mixture to form carbide and develop strength. Particularly suitable for areas requiring high strength. The amount of metal silicon and metal aluminum added is preferably the total amount or 1 to 10% by weight each,
If it is less than 1% by weight, no strength will be developed, and if it exceeds 10% by weight, corrosion resistance will decrease, which is not preferable.

Next, the method for manufacturing the refractories used in the present invention (C) will be explained. Pitch tar or IT phenol resin is added as a binder to the above formulation, kneaded and formed, and then heated and dried.

The refractory used in the present invention may be unfired in order to obtain a firing effect during use, or it may be fired at a temperature that does not impede the stability of β-alumina.

Alternatively, it may be fired in a carbon/nitrogen atmosphere to react with metal silicon in the formulation to form a silicon carbide/silicon nitride bond.

Natural graphite, electrode scraps, coke, and carbon black are used as the carbon material, and carbides and nitrides preferably have a purity of 80% or more, preferably <90% or more.

There are β-alumina stabilized with Na2O and 20, but it is preferable to use one stabilized with Na20 in an atmosphere where NIL20 vapor is present.

The refractory used in the present invention has the following characteristics compared to conventional refractories.

■ At203 quality, Az2o3- sic - in an atmosphere where alkali vapor of NazO/K2O exists.
N like quality! L20 (K2O) +11 At20
3 → Na2o(K2O) e 11 There is no risk of expansion and collapse associated with the reaction of At203.

■ Excellent oxidation resistance compared to magnesia carbon and alumina carbon. That is, carbides and nitrides are oxidized and react with Na2O'K2O in β-alumina, forming an oxide film on the refractory surface and suppressing carbon oxidation. Carbides and nitrides are both highly refractory minerals unless oxidized, so carbonaceous refractories containing glass powder as an antioxidant also have excellent strength and corrosion resistance at high temperatures.

Due to the above characteristics, the molten metal processing vessel of the present invention lined with this refractory can have a long life.

Next, examples of the present invention will be explained with reference to Table 1 and the second light.

After mixing and kneading the compounding ratios shown in Table 1 and Table 2, the mixture was molded and dried by heating at 250° C. for 8 hours.

Note that comparative examples were also conducted in the same manner. Table 1 shows the results of measuring the characteristic values of these samples.

As shown in Table 2. Note that oxidation resistance, slag resistance, and sylq IJ resistance were simultaneously measured using the following methods.

Stretch the rod-shaped specimens together so that the inner surface becomes a polygonal prism.
Ca(LFeO, CaF2+ Na2CO3+ 8
Synthetic slag with a weight ratio of 102 of 4:4:1:l:4 was melted at 1500°C in a separate container and then heated at 1500°C for 1 hour. Thereafter, the slag was removed, and air was blown onto the inner surface for 15 minutes to forcibly cool and oxidize. After repeating this operation five times, it was cut to measure the dimensions of erosion and the thickness of the decarburized layer, and the state of cracks was observed.

In Examples 1 to 8 of the present invention, Comparative Example J Niji also showed good results in corrosion resistance, spalling resistance, and oxidation resistance.

The refractory lining of the present invention may be placed completely in the molten metal processing vessel when the synthetic slag is placed at the bottom or when injected within the hot water chamber, or it may be placed above the hot water surface. If only 1 stone is added, it may be small (at least 17 linings are needed in the nura line part).

As is clear from the above description, the lining refractory for molten metal processing vessels of the present invention is composed of 80% β-alumina, Kurofune 10%
By using Example 1 with 10% by weight of silicon carbide, the container was lined with a synthetic slag of Na2CO3 + FeO + CaO + CaF2, which extended the life of the container, improved the operating rate, and contributed to industry. There was a lot to do.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship with oxidation resistance, and Figure 2 is a characteristic diagram showing the relationship with oxidation resistance.
It is a chart showing the relationship between silicon carbide, graphite, and corrosion resistance in the refractory lining of the molten metal processing vessel of the present invention.

Claims (1)

[Claims] 1. β-alumina: 30 to 94% by weight, carbon material: 3
-40% by weight, carbide and/or nitride: 3-30% by weight, lining for a molten metal processing vessel. 2. In addition to β-alumina, magnesia, zirconia,
At least one or two or more of magnesia alumina spinel, alumina, L-light, zircon, fused silica oxide, and double oxide: 30-94% by weight, carbon material: 3-94% by weight
40% by weight, carbide and/or nitride: 3-30% by weight
Lining υ of a molten metal processing container characterized by containing
Material.