Resin-bonded liner

Abstract

In the continuous casting of molten metal, the invention describes a refractory article for reducing deposition of inclusions on a surface contacting the stream of molten metal. The article comprises a first composition and a second composition on at least a portion of the contacting surface. The second composition includes a resin-bonded refractory composition comprising a refractory aggregate and a reactive metal. The resin-bonded refractory composition reduces deposition of inclusions relative to standard carbon-bonded or castable refractories. The second composition is particularly effective as a nose of a stopper rod or a liner for a nozzle, shroud or slide gate plate.

Description

[0001] The present invention relates to refractory articles that are used in the casting of steel, and particularly to such articles that are resistant to deposition onto the article's walls of inclusions such as, for example, alumina and titania.DESCRIPTION OF THE RELATED ART[0002] In the continuous casting of steel, refractory articles permit the transfer of molten steel between various containers, notably between the ladle and the distributor, and the distributor and the continuous casting mold. Such articles include, but are not limited to, stopper rods, shrouds, nozzles, and slide gate plates.[0003] Refractory articles direct the flow of molten steel but also protect the steel from oxygen, which can reduce the quality of the steel. Despite these precautions, considerable amounts of oxygen can still dissolve in and react with the molten metal. Dissolved oxygen can precipitate from the steel and react with carbon to produce carbon monoxide. These gases create undesirable porosity...

AI Technical Summary

Problems solved by technology

Refractory articles direct the flow of molten steel but also protect the steel from oxygen, which can reduce the quality of the steel.

Despite these precautions, considerable amounts of oxygen can still dissolve in and react with the molten metal.

These gases create undesirable porosity, cracks and internal defects, which lower the quality of the finished steel.

Deposition in the casting channel of a nozzle, shroud or slide gate plate can clog the casting channel and substantially reduce the flow of molten steel.

Articles may be unclogged using an oxygen lance; however, lancing disrupts the casting process, reduces refractory life, and decreases casting efficiency and the quality of the steel produced.

A total blockage of the casting channel by alumina decreases the expected life of the article and is very costly and time-consuming to steel producers.

For example, steel having an initially high dissolved oxygen content can limit a shroud to 2-3 ladles due to heavy alumina buildup in the casting channel.

Unfortunately, gas injection requires large volumes of inert gas, complicated refractory designs, and is not always an effective solution.

Inert gas at high pressure may also dissolve into the molten metal causing pinhole defects in the steel.

Their high thermal expansion coefficients can also cause surface cracking.

For these reasons, the useful life of the surface layer is limited.

Unfortunately, CaO does not diffuse to the surface quickly enough to be completely effective.

Despite these benefits, SiAlON-graphite refractories are expensive, and graphite makes the composition susceptible to oxidation.

Although eliminating problems associated with carbon oxidation, the preheating regime necessary to burn off the carbon and effect the required compositional changes is not always practical.

AlN-bonded refractories are purportedly resistant to alumina deposition, oxidation, erosion, do not promote reactions associated with alumina deposition, are resistant to thermal shock, and are not readily wetted by molten steel.

This process is both dangerous, due to the presence of a reactive metal powder, expensive, and time consuming.

Low conductivity insulates the molten steel and reduces the likelihood of steel freezing in the nozzle.

Limitations on the amount of reactive metal include cost and hazardousness.

Reactive metals are generally more expensive than refractory aggregates and, especially as powders, reactive metals can be explosive during processing.

Firing tends to destroy the resin binder and reactive metal components.

During firing, the binder can oxidize, thereby reducing the physical integrity of the article, and the reactive metal can form undesirable compounds.

An article comprising aluminum carbide is susceptible to hydration and destructive expansion.

Aluminum oxide does not inhibit and may actually accelerate alumina deposition.

In either case, the beneficial effect of aluminum metal is lost.

Carbides can cause cracking in the article during preheating.

Resin-bonded compositions can also be more susceptible to cracking caused by thermal shock than carbon-bonded or cast materials.

A refractory article should not consist essentially of a resin-bonded composition because such an article could have a tendency to crack because of thermal effects during preheating and casting operations.

The severity of cracking ranges from problematic for tundish well nozzles to catastrophic for submerged entry nozzles and shrouds.

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