GB2171625A - Duct for molten metal - Google Patents

Abstract

A metal-pouring tubular shroud, or other refractory duct for conducting molten metal, has a graphite alumina wall (3) with a bore lined by compressed fibrous refractory material (4) to improve resistance to thermal shock and molten metal erosion. <IMAGE>

Description

SPECIFICATION Furnace refractory duct This invention relates to furnace refractory ducts, for conducting molten metal, and its object is to provide such a duct with high thermal shock resistance, to withstand initial impact of molten metal, and high resistance to erosion by flow of molten metal.

The invention will be described as applied to a tubular shroud between the outlet nozzle of a pouring ladle and a tundish feeding molten metal, such as steel, to continuous casting apparatus.

Such shrouds are usually made of an alumina graphite refractory material by moulding or pressing a thermosetting resin or pitch bonded mix in which the binder is carbonised when the shrouds are fired.

One known method of improving the resistance of such shrouds to thermal shock and erosion is to provide the shroud bore surface with a high alumina coating.

This may be achieved by so-called "perishing" of the bore surface during manufacture to produce an alumina-rich layer of a somewhat friable character on the surface of the shroud bore, to a depth of 1 or 2mm. Such a friable alumina-rich layer is found to withstand the initial contact by molten metal, when pouring starts, and produces a bore surface resistant to erosion.

Another method of coating a shroud bore is to cast a high alumina slip down the bore.

The present invention provides an improved lining for a shroud bore, or like furnace refractory duct, having improved thermal shock resistance, and a method of manufacture thereof.

According to the invention, the bore surface of a metal-pouring tubular shroud, or like furnace refractory duct, is provided with an alumino-silicate or like fibrous rfractory lining. Preferably the lining is compressed to a density in the range 300 to 1200 Kg/cu. metre.

Preferably the fibrous refractory is compressed, so as to reduce its thickness in the ratio of 2-4:1, preferably 3:1, from the relatively low density or open structural form in which such fibrous refractory material is usually produced, such as by a process of vacuum forming from an aqueous suspension of fibrous refractory material and binders such as starch, clay and colloidal silica.

The preferred method of manufacture according to the invention is to cover a mandrel with a sleeve of uncompressed fibrous refractory material of a given thickness and then form around the sleeve the alumina graphite tubular shroud, or other duct, by press moulding, to achieve the required reduction in thickness, and thus density, of the fibrous refractory material formed as a bore lining, and to bond the fibrous refractory material to the alumina graphite material.

The fibrous refractory sleeve may be preformed and placed on the mandrel but can more economically be assembled or built up from ring sections or wrapped fibrous blanket, sheet or paper.

The alumina graphite tubular shroud is preferably isostatically pressed on to the sleeved mandrel to the required density of the shroud and to achieve the required compression of the fibrous refractory bore lining.

It is to be expected that on initial pouring of steel the fibrous lining will be damaged or even destroyed, but will survive for a sufficient period of time to provide protection of the main body of the shroud from the harmful effects of thermal shock.

The main body of the shroud will subsequently withstand erosion by the molten steel.

The invention is illustrated by way of example on the acompanying drawing in which: Figure 1 is an axial section of part of a tubular shroud for pouring steel from a ladle, and Figure 2 is an axial section of mandrel with fibrous refractory sleeve sections assembled thereon before forming of a shroud.

As shown in Figure 1, a nozzle 1, of a bottompouring steel ladle, leads into the hopper mouth 2 of a tubular refractory shroud of which the cylindrical wall 3 has a bore lining 4 of compressed fibrous refractory material.

Figure 2 shows a mandrel 5 on to which are assembled scarf-jointed ring sections 6 of a sleeve of fibrous refractory material of some three times the thickness of the lining 4 to which the fibrous material is compressed by pressing of alumina graphite material around the sleeved mandrel to form the shroud.

1. A metal-pouring tubular shroud, or other molten metal conducting furnace refractory, of which the bore, or other metal-contacted surface, is provided with an alumino-silicate or like fibrous refractory lining, preferably compressed to a density in the range 300 to 1200 Kg/cu. metre.

2. A furnace refractory duct according to Claim 1, in which the fibrous refractory material has been compressed by the process of manufacture of the furnace refractory duct.

3. A furnace refractory duct according to Claim 1 or 2, in which the main body of the furnace refractory duct is composed of an alumina graphite material.

4. A method of making a furnace refractory duct according to Claim 2 or 3, in which a mandrel is covered with a sleeve of uncompressed fibrous refractory material of a given thickness and there is then formed around the sleeve the furnace refractory duct by press moulding to achieve a required reduction in thickness of the fibrous refractory material.

5. A metal-pouring tubular shroud with a fibrous refractory bore lining made substantially as described and illustrated.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Furnace refractory duct This invention relates to furnace refractory ducts, for conducting molten metal, and its object is to provide such a duct with high thermal shock resistance, to withstand initial impact of molten metal, and high resistance to erosion by flow of molten metal. The invention will be described as applied to a tubular shroud between the outlet nozzle of a pouring ladle and a tundish feeding molten metal, such as steel, to continuous casting apparatus. Such shrouds are usually made of an alumina graphite refractory material by moulding or pressing a thermosetting resin or pitch bonded mix in which the binder is carbonised when the shrouds are fired. One known method of improving the resistance of such shrouds to thermal shock and erosion is to provide the shroud bore surface with a high alumina coating. This may be achieved by so-called "perishing" of the bore surface during manufacture to produce an alumina-rich layer of a somewhat friable character on the surface of the shroud bore, to a depth of 1 or 2mm. Such a friable alumina-rich layer is found to withstand the initial contact by molten metal, when pouring starts, and produces a bore surface resistant to erosion. Another method of coating a shroud bore is to cast a high alumina slip down the bore. The present invention provides an improved lining for a shroud bore, or like furnace refractory duct, having improved thermal shock resistance, and a method of manufacture thereof. According to the invention, the bore surface of a metal-pouring tubular shroud, or like furnace refractory duct, is provided with an alumino-silicate or like fibrous rfractory lining. Preferably the lining is compressed to a density in the range 300 to 1200 Kg/cu. metre. Preferably the fibrous refractory is compressed, so as to reduce its thickness in the ratio of 2-4:1, preferably 3:1, from the relatively low density or open structural form in which such fibrous refractory material is usually produced, such as by a process of vacuum forming from an aqueous suspension of fibrous refractory material and binders such as starch, clay and colloidal silica. The preferred method of manufacture according to the invention is to cover a mandrel with a sleeve of uncompressed fibrous refractory material of a given thickness and then form around the sleeve the alumina graphite tubular shroud, or other duct, by press moulding, to achieve the required reduction in thickness, and thus density, of the fibrous refractory material formed as a bore lining, and to bond the fibrous refractory material to the alumina graphite material. The fibrous refractory sleeve may be preformed and placed on the mandrel but can more economically be assembled or built up from ring sections or wrapped fibrous blanket, sheet or paper. The alumina graphite tubular shroud is preferably isostatically pressed on to the sleeved mandrel to the required density of the shroud and to achieve the required compression of the fibrous refractory bore lining. It is to be expected that on initial pouring of steel the fibrous lining will be damaged or even destroyed, but will survive for a sufficient period of time to provide protection of the main body of the shroud from the harmful effects of thermal shock. The main body of the shroud will subsequently withstand erosion by the molten steel. The invention is illustrated by way of example on the acompanying drawing in which: Figure 1 is an axial section of part of a tubular shroud for pouring steel from a ladle, and Figure 2 is an axial section of mandrel with fibrous refractory sleeve sections assembled thereon before forming of a shroud. As shown in Figure 1, a nozzle 1, of a bottompouring steel ladle, leads into the hopper mouth 2 of a tubular refractory shroud of which the cylindrical wall 3 has a bore lining 4 of compressed fibrous refractory material. Figure 2 shows a mandrel 5 on to which are assembled scarf-jointed ring sections 6 of a sleeve of fibrous refractory material of some three times the thickness of the lining 4 to which the fibrous material is compressed by pressing of alumina graphite material around the sleeved mandrel to form the shroud. CLAIMS

1. A metal-pouring tubular shroud, or other molten metal conducting furnace refractory, of which the bore, or other metal-contacted surface, is provided with an alumino-silicate or like fibrous refractory lining, preferably compressed to a density in the range 300 to 1200 Kg/cu. metre.

2. A furnace refractory duct according to Claim 1, in which the fibrous refractory material has been compressed by the process of manufacture of the furnace refractory duct.

3. A furnace refractory duct according to Claim 1 or 2, in which the main body of the furnace refractory duct is composed of an alumina graphite material.

4. A method of making a furnace refractory duct according to Claim 2 or 3, in which a mandrel is covered with a sleeve of uncompressed fibrous refractory material of a given thickness and there is then formed around the sleeve the furnace refractory duct by press moulding to achieve a required reduction in thickness of the fibrous refractory material.

5. A metal-pouring tubular shroud with a fibrous refractory bore lining made substantially as described and illustrated.