JPH03295867A - Castable refractory material for lining receiving port of torpedo ladle car - Google Patents

Abstract

PURPOSE:To improve the resistance of the refractory material to corrosion, spalling and oxidation by incorporating zirconia, other refractory materials and a binder to a large amt. of silicon carbide. CONSTITUTION:The refractory material contains >=50wt.% silicon carbide, 3-20wt.% zirconia and the balance other refractory materials and binder. Although the balance mixed is not specifically limited, an alumina-based material such as electrofused alumina, sintered alumina, bauxite and aluminous shale and a chamotte material are used as the main material, a carbon material such as coal pitch, petroleum pitch, artificial graphite and coal or petroleum- based coke are used as the auxiliary material. The alumina cement, superfine silica and clay which are ordinarily used as a castable material, a dispersant such as condensed alkali phosphate and sodium polycarboxylate for imparting workability of the refractory material and a small amt. of metallic aluminum for imparting resistance to spalling in brief drying are added as a binder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a poured refractory for lining the pig iron receiving port of a pig iron mixer car for transporting hot metal.

[Prior Art] Pig-mixing cars have traditionally been used as transport containers, but in recent years, hot metal pretreatment has been carried out with the main purpose of desiliconization and dephosphorization, and they are increasingly being used as reaction vessels. It's coming. For this reason, in addition to the erosion effect caused by the slag components, thermal spalling occurs at the receiving port of the pig iron mixer due to repeated receiving and discharging of hot metal, resulting in increased wear and a shortened service life. Therefore, there is a demand for the development of a refractory material that has excellent corrosion resistance and spalling resistance.

Conventionally, as this type of material, A1.03S102-based materials using alumina cement or fireclay as a binder have been widely used. However, this type of material does not have sufficient slag resistance and spalling resistance, which causes problems such as large melting loss and easy peeling. For this reason, although JP-A-62-36073 proposes improving corrosion resistance and spalling resistance by adding silicon carbide, the amount of silicon carbide added is as small as 0.5 to 5% by weight. Currently, it has insufficient corrosion resistance and spalling resistance, and cannot cope with increasingly severe operations.

For this reason, attempts have been made to use a large amount of silicon carbide, which has a small coefficient of thermal expansion and poor wettability with slag, but the corrosion resistance deteriorates due to oxidation of silicon carbide during use, which is undesirable. Although the addition of B, C, and BN is proposed in, for example, JP-A-58-151369 for the purpose of improving the sintering property, it is not preferable because it significantly improves the sinterability and deteriorates the spalling resistance.

[Problems to be Solved by the Invention] The problems to be solved by the present invention are as a result of various studies in order to obtain a pouring material for the lining of a mixed pig iron car receiving hole that has stable durability. A highly durable pouring material for lining the pigtail hole of a mixed pig iron car, which provides spalling properties and prevents oxidation of silicon carbide by adding zirconia, and also provides oxidation resistance without impairing durable polling properties. It is about providing.

[Means for Solving the Problems] The present invention includes silicon carbide of 50% by weight or more and zirconia of 3 to 20% by weight.
This is a cast refractory for lining a mixed pig iron car receiving pigtail hole, characterized in that it contains % by weight and the remainder is blended with other refractory materials and binders.

[Function] The silicon carbide blended in the present invention has the function of improving corrosion resistance and spalling resistance. The silicon carbide used here usually has a raw coal content of 95% or more, but can be used if it has a purity of 80% or more. If it is less than that, it is not preferable because it causes an increase in construction moisture, resulting in structural deterioration and a decrease in corrosion resistance.

The reason why the amount of silicon carbide is regulated to 50% by weight or more is that if it is less than 50% by weight, the effect of improving corrosion resistance and spalling resistance is poor, and preferably 50 to 90% by weight.
This is because compositions in which the composition is good, that is, more than 90% by weight, are practically difficult to manufacture because it is necessary to add a binder, etc., which are essential to the pouring material.

Next is zirconia, which is incorporated into the present invention.

Application of this material has the function of suppressing high-temperature oxidation of silicon carbide. Although the details of the reason for this oxidation resistance imparting effect are unknown, the Si and glass produced by the oxidation of silicon carbide by the addition of zirconia are originally network-forming oxides and have high viscosity, but they can be used as binders. Due to the presence of CaO contained in the alumina cement used,
This CaO has a function as a network modification oxide, so it is a Sin.

Reduces the viscosity of glass. Here, the addition of zirconia prevents the above-mentioned decrease in viscosity since the material is an intermediate oxide. Or zirconia particles or Ca
O-ZrO2 is Sio, am in glass, Sin,
It is thought that the oxidation resistance is improved because the viscosity of the glass on the silicon carbide surface becomes difficult to decrease due to the effect of 0 or more alone or in synergy to increase the apparent viscosity of the glass.

The zirconia used here can be either natural or synthetic, and the synthetic zirconia can be stabilized by adding CaO, MgO, etc., or partially stabilized.

Regarding particle size, S produced by oxidation of silicon carbide
in, 0.21+s for the purpose of suspension in glass
Particle sizes finer than m are preferred.

The reason why the amount of zirconia is restricted to 3 to 20% by weight is that less than 3% by weight contributes little to oxidation resistance;
This is because a composition with a larger amount causes deterioration in corrosion resistance.

There are no particular regulations regarding the remaining blend, but alumina raw materials such as fused alumina, sintered alumina, bauxite, and band shale, or chamots raw materials can be used as the main raw material, and 1. coal-based pitch,
Carbon raw materials such as petroleum pitch, scaly graphite, artificial graphite, raw graphite, five-carbon coke, and petroleum coke can be used. Binding materials include alumina cement, ultrafine silica, and clay, which are usually used in pouring materials, as well as dispersants such as alkali condensed phosphate and sodium polycarboxylate to impart workability to refractories, and for short drying times. A small amount of metal aluminum or the like can be added to provide explosion resistance.

[Example] Table 1 shows the corrosion resistance, spalling resistance, and
The results of an investigation into the effect on oxidation resistance are shown below.

In the same table, the corrosion index is expressed as an index with the sample No. 1 as 100, and the smaller the number, the less the amount of erosion. Erosion was performed at 10 cycles of 30 minutes at ℃ and evaluated by the amount of erosion.

To evaluate oxidation resistance, a sample adjusted to a predetermined softness is cast into a 40 x 40 x 160 mm metal frame, and after hardening,
Dry at 10℃×24hrs, 1500℃×10hrs
After firing, the thickness of the oxidized layer on the surface layer of the cross section was measured.

Spalling resistance was determined by observing the state of the sample after 10 cycles using a panel spalling test method, in which one cycle was heating at 1600° C. for 15 minutes, water cooling for 5 minutes, and air cooling for 5 minutes.

From the same table, test sample Nos. 4 to 4 which are examples of the present invention
Test sample No. 8 shows good results in corrosion resistance and spalling resistance, and is a conventional comparative example test sample No. 10.
It can be seen that they have the same oxidation resistance when compared.

Table 2 shows the results of an investigation into the effects of varying the mixing ratio of silicon carbide and fused alumina on corrosion resistance, spalling resistance, and oxidation resistance. From the surface, the amount of silicon carbide added is 50
It can be seen that good results are shown at weight % or higher.

When Test Sample No. 5, which is a product of the present invention, was lined in the receiving port of a pig iron mixer car, it was found that it had an improved effect in terms of corrosion resistance and spalling resistance compared to Test Sample No. 001, which is a conventional product, and its durability was also improved. It has become possible to extend the lifespan by approximately twice that of conventional products.

[Effects of the Invention] The monolithic refractories of the present invention can provide the following effects.

■When using a large amount of silicon carbide, the conventional technology of adding antioxidants such as B4C is effective in improving oxidation resistance and corrosion resistance, but there are problems with spalling resistance. However, the refractory of the present invention has
The use of zirconia makes it possible to impart oxidation resistance without impairing spalling resistance.

Claims (1)

[Claims] Silicon carbide 50% by weight or more, zirconia 3-20% by weight
A poured refractory for lining a mixed pig iron car receiving pigtail hole, characterized in that the remaining part is blended with other refractory materials and binders.