ES2299056T3 - SHUTTER BAR TO SUPPLY GAS TO A FUSED METAL. - Google Patents

Abstract

Shutter bar adapted to deliver gas during the pouring of molten metal, comprising a shutter bar body having an internal chamber (1) and a gas discharge opening (2), a hole (3) that connects the internal chamber ( 1) to the gas discharge opening (2), the internal chamber (1) and the orifice (3) defining a gas passageway, characterized in that the walls of the gas passageway are provided with a layer (4 ) that does not produce carbon monoxide at the temperature of use.

Description

Shutter bar to supply gas to a metal molten.

This invention relates to a shutter bar monobloc used to control the flow of molten metal from a discharge nozzle in a container container during emptying of metal

In continuous casting procedures, the use of gases injected down the shutter bar has been shown which has significant benefits in the quality of the metal that It is straining. For example, inert gases can be injected, such such as argon or nitrogen, to reduce problems due to formation and alumina jam or to help remove solidification products near the nozzle of discharge. Reactive gases can also be used when the Molten composition needs modification. Conventionally, the shutter bar - usually made of a refractory composition alumina and carbon- is provided with an internal chamber connected to gas supply means at one end and at a gas discharge opening at the other end.

Various systems have been developed to ensure that a precisely measured gas flow is supplied to the shutter bar Problems have been found with the sealing of such systems and by ensuring that the gas follows its trajectory projected and not wasted. The shutter bars that have proven successful in meeting many of these requirements is described in the documents EP-A2-358 535, WO-A1-00 / 30785 and WO-A1-00 / 30786 and, more recently in the document WO-A1-02 / 100579.

Continuing with his works of improvement in this field, the applicant has now been given notice that the gas injected into the molten metal through the shutter bar could become contaminated when it passes through the same.

In particular, carbon is suspected present in the composition that constitutes the bar body shutter could reduce some of the metal oxides present, also, in the composition; this reduction is accompanied by the Carbon monoxide generation. Injected Carbon Monoxide in molten metal oxidizes, in turn, the aluminum that has been added to calm the steel, thereby producing significant quantities alumina thus contributing to the formation and jamming of alumina.

Therefore, it would be advantageous to provide a shutter bar that will not contaminate the gas that passes through it.

According to the invention, this problem is solved. for a shutter bar adapted to supply gas during pouring molten metal comprising a sealing rod body which has an internal chamber and a gas discharge opening, a hole that connects the internal chamber to the discharge opening of gas, defining the internal chamber and the orifice a passage duct Of gas. According to the invention, the walls of the gas passage duct they are provided with a layer of a material that does not produce monoxide of carbon at the temperature of use.

It should be noted that it is, as far as you know the applicant, the first time you intend to provide an article refractory with such a layer on a portion of said article, which will never get in touch with molten metal. On the contrary, in prior art, as illustrated for example in the document US-A1-5.691.061 or in the US-A1-5.681.499, such a layer is arranged only on portions that are always in contact with the metal.

The layer can be formed as a coating applied on the walls of the gas passage duct after the manufacturing of the shutter bar. Such coating can be apply by spraying a liquid, a wet or semi-wet composition or, simply filling the inner chamber with the composition appropriate. Once the coating is dry, it can be cured Then the shutter bar. Alternatively, the cure of the shutter bar can take place before the stage of coating. Advantageously, the layer is a pressed trim simultaneously with the shutter bar body. In this case, it is possible, actually, reduce the number of manufacturing stages. According to another variant, the layer essentially extends through the entire thickness of the walls of the gas passage duct.

The material that constitutes the layer, which does not produces carbon monoxide at the use temperature, it can be select from three different categories of materials:

a) non-carbon materials;

b) materials consisting essentially of non-reducible refractory oxides; or

c) materials comprising elements that react with the generated carbon monoxide. Preferably, the Selected material will present two or three of the properties previous.

Silica (for example, vitreous silica), alumina, material (spinel) with mullite base or magnesia are examples of suitable material of the first category. In certain cases, these materials may, however, be somewhat difficult to apply as trim or lining (lack of carbon in the layer can cause some thermal shock problems) and not they constitute the preferred embodiment of the invention.

Pure alumina carbon compositions are, for example, suitable materials of the second category. In In particular, these compositions should contain very low silica or conventional impurities found usually on silica (sodium or potassium oxide). In In particular, silica and its conventional impurities should be keep below 2% by weight, preferably below 1% by weight.

Suitable materials of the third category they comprise, for example, a free metal capable of combining with carbon monoxide to form a metal oxide and a carbon free. Silicon and aluminum are suitable for this application. These materials may also or alternatively comprise carbides or nitrides capable of reacting with carbon monoxide (by example, silicon or boron carbides).

Preferably, the selected material belongs to the second or third category, even more preferably, it belongs to the second and third categories.

A suitable material that constitutes the layer, which does not produce carbon monoxide at the use temperature, it can comprise 60 to 88% by weight alumina, 10 to 20% by weight graphite and 2 to 10% by weight silicon carbide. Such material consists essentially of non-oxidized species or non-reducible oxides and comprises silicon carbide that can react with carbon monoxide, if something is generated, in working conditions.

The invention will now be described with reference. to the attached drawing, in which figure 1 shows a section cross section of a shutter bar according to the invention. The reference 1 represents, respectively, the internal chamber and a gas discharge opening of the shutter bar. A hole 3 connect the internal chamber 1 to the gas discharge opening 2. He hole 3 and internal chamber 1 define a passageway of the gas. Figure 1 represents an embodiment in which layer 4 has been co-pressed as a trim with the bar body shutter Very conveniently, the trim 4 can be consisting of several preformed tubular portions 41, 42, 43 which are all co-pressed with the shutter bar body. Be represents a portion of the metal rod 5 that connects the shutter bar to the rigging device (not shown) in work position. Preferably, the metal rod 5 is extends beyond the highest point of layer 4. Even more preferably, a seal 6 is inserted around the lower end of the metal rod 5.

Claims (9)

1. Shutter bar adapted to supply gas during the pouring of molten metal, comprising a shutter bar body having an internal chamber (1) and a gas discharge opening (2), a hole (3) connecting the chamber internal (1) to the gas discharge opening (2), the internal chamber (1) and the orifice (3) defining a gas passageway, characterized in that the walls of the gas passageway are provided with a layer (4) that does not produce carbon monoxide at the temperature of use. 2. A sealing bar according to claim 1, characterized in that the layer (4) is a trim co-pressed with the body. 3. Seal bar according to claim 1, characterized in that the layer (4) is a coating applied on the walls of the gas passage duct. 4. Seal bar according to claim 1, characterized in that the layer (4) extends essentially throughout the entire thickness of the walls of the gas passage duct. 5. Shutter bar according to any one of claims 1 to 4, characterized in that the layer (4) extends upward beyond the lowest point reached by a metal rod (5) used to secure the shutter bar to a device for rig. 6. Seal bar according to any one of claims 1 to 5, characterized in that the material constituting the layer (4) is selected from the groups of a) non-carbon materials; b) materials consisting essentially of non-reducible refractory oxides; I c) materials comprising elements that react with the generated carbon monoxide, or mixtures of same. 7. The sealing bar according to any one of the preceding claims, characterized in that the layer (4) comprises from 60 to 88% by weight of alumina, from 10 to 20% by weight of graphite and from 2 to 10% by weight of carbide of silicon. 8. Set of a shutter bar according to a any of the preceding claims, with a rod (5) of metal used to fix the shutter bar to a device rig, in which the metal rod (5) extends beyond the highest point of the layer (4). 9. Assembly according to claim 8, wherein a sealing gasket (6) is inserted around the end Bottom of the metal rod (5).