WO2012126058A1

WO2012126058A1 - A refractory brick

Info

Publication number: WO2012126058A1
Application number: PCT/AU2012/000297
Authority: WO
Inventors: Robert John WELLHAM; Michael Robert WELLHAM
Original assignee: Coolan Trading Pty Limited
Priority date: 2011-03-21
Filing date: 2012-03-21
Publication date: 2012-09-27

Abstract

A refractory brick for lining a metal making furnace, ladle or the like, the refractory brick including: a main body with an exposed face, the exposed face being a surface of the refractory brick that is exposed to oxygen air when the refractory brick is part of a refractory lining; and a metal cover affixed to the main body, the metal cover substantially covering the exposed face.

Description

A REFRACTORY BRICK

Field of the invention

The present invention relates to refractories and refractory bricks for lining metal making furnaces, ladles and the like. ·

Background of the invention

Refractories containing carbon are commonly used to line iron making and steel making furnaces and ladles. Exposure to oxygen in air at elevated temperatures causes the carbon to oxidize which has a detrimental effect on the ultimate life of the refractory.

One method of reducing oxidation includes the addition of anti-oxidation materials such as aluminium, silicon, silicon carbide, aluminium and silicon alloys and boron compounds.

Another method is to apply a paint or coating to the surface of the refractory which forms a low permeability layer on the surface thereby restricting the ability of oxygen to contact the refractory. In iron or steel making furnaces and ladles the "hot face" of the refractory is the surface exposed to the molten iron or steel. This surface is often subjected to significant oxidation during pre-heating of the new lining. Preheating is a process of heating the lining to a high temperature before use to reduce the incidence of spalling due to thermal shock when contacted with molten iron or steel. Preheating also reduces the incidence of iron or steel solidifying when initially contacting a cold refractory lining thereby avoiding the formation of "skulls" of solid iron or steel on the refractory lining. During the preheating phase oxidation of carbon can occur up to a depth 20~30mm.

During operation the liquid iron or steel can provide a barrier to oxidation at the hot face. After the first use of the furnace or ladle the hot surface of the refractory is often covered with a layer of metal or slag which can then act as a low permeability layer when the furnace or ladle is empty. The "back face" or "cold face" of the refractory lining is the surface of the refractory at the back of the lining and not in contact with the molten iron or steel. Oxidation of the back face can occur if the back of the refractory lining becomes sufficiently hot. The back face may continue to oxidize throughout the life of the refractory lining. Oxidation of carbon at the back face often occurs up to a depth of 30~40mm.

Lining thicknesses can vary from approximately 1 15mm to 300mm in iron and steelmaking ladles and from approximately 200mm up to 1200mm in steel making furnaces. The reduction in effective thickness of the linings due to carbon oxidation may be up to 40% in some processes.

Summary of the invention

In one broad from the present invention provides a refractory brick for forming a refractory lining, the refractory brick including a metal cover affixed thereto such that when the refractory brick is part of the refractory lining, the metal cover at least partly covers the hot and/or cold face of the refractory brick.

In a further broad form the present invention provides a refractory brick for lining a metal making furnace, ladle or the like, the refractory brick including: a main body with an exposed face, the exposed face being a surface of the refractory brick that is exposed to oxygen when the refractory brick is part of a refractory lining; and a metal cover affixed to the main body, the metal cover at least partly covering the exposed face. In one form, the metal cover covers substantially all of the exposed surface.

In another form, the oxygen is from heated and/or surrounding air. In a further form, the metal cover has at least one anchor for affixing the metal cover to the main body.

In another form, the anchor is a projection formed by punching a hole in the metal cover. In another form, the metal cover extends from the exposed face to an adjacent face, and at least partly covers the adjacent face.

In a further form the main body is formed of a ceramic material. According to another form the metal cover is a metal plate. In a further form the metal plate is made from steel.

In one form, the exposed face is the surface that forms part of the hot face of the refractory lining.

In another form, the exposed face is the surface that forms part of the cold face of the refractory lining. In a further form, the refractory brick further includes: a second exposed face; and a second metal cover affixed to the main body, the second metal cover at least partly covering the second exposed face. In a further broad from the present invention provides a refractory lining for a metal making furnace, ladle or the like, the refractory lining including a plurality of the refractory bricks as described above. In a further broad from the present invention provides a refractory lining for a metal making furnace, ladle or the like, the refractory lining including a metal cover attached to the hot and/or cold face of the refractory lining, such that a substantial portion of the hot and/or cold face of the refractory lining is covered by the metal cover. In one form the refractory lining is formed from a plurality of refractory bricks.

In a further form, metal cover is a steel plate.

In a further broad form the present invention provides a method for reducing oxidation at the hot and/or cold face of a refractory lining formed of a plurality of refractory brick^'s, the method including securely positioning one or more metal covers on one or more exposed faces of the refractory bricks, the exposed faces being those faces of the bricks that form part of the hot and/or cold face of the refractory lining. In one form the metal cover is a steel plate. .

In a further broad form the present invention provides a method for affixing a metal plate to a refractory brick, the method including the steps of: punching holes in the metal plate such that projecting anchors are formed in the metal plate; positioning the metal plate in a brick mould; and filling the brick mould with refractory material. In a further broad form the present invention provides a metal plate for attachment to an a refractory brick, the metal plate including an anchor for affixing the metal plate to the refractory brick. In one form, the anchor is a projection formed by punching a hole in the metal plate. In one form the metal plate has a substantially L-shaped profile.

In a further broad form, the present invention provides a system for reducing oxidation at the hot and/or cold face of a refractory lining formed of a plurality of refractory bricks, the method including securely positioning one or more metal covers on one or more exposed faces of the refractory bricks, the exposed faces being those faces of the bricks that form part of the hot and/or cold face of the refractory lining.

Brief Description of the Drawings

Examples of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a side view of a refractory brick with steel plate attached;

Figure 2 is a top view and sectional view of a refractory brick with steel plate attached to the hot and back faces; Figures 3A to 3D illustrate a method of affixing the metal plate;

Figure 4 shows a brick heated with metal cover after being heated to 1 100°C and held for 4 hours; and Figure 5 shows refractory bricks with steel plates after being heated to 1 100°C and held for 4 hours. Detailed Description

Embodiments of the present invention provide a refractory brick for forming a refractory lining, the refractory brick including a metal cover affixed thereto. The metal cover at least partly covers the hot and/or cold face of the refractory brick when the brick is part of a refractory lining.

Typically the refractory brick is for lining a metal making furnace, ladle or the like. For example, the refractory brick would typically include a main body with an exposed face, the exposed face being a surface of the refractory brick that is exposed to oxygen when the refractory brick is part of a refractory lining (for example the hot or cold face). The metal cover is positioned to at least partly cover the exposed face(s) and thereby reduce oxidation of the bricks.

In a preferred embodiment thin steel plates are fixed to the hot face and/or the cold face of refractory bricks. By providing a physical barrier, these plates significantly reduce the ability of oxygen (for example, from heated or surrounding air) to come into contact with the hot face and/or back face of the refractory and thereby reduce oxidation.

Figures 1 and 2 illustrate a refractory brick ( 1) having steel plates (2) attached to the main body (3). The steel plates are attached to the hot (4) and back (cold) faces (5) of the refractory brick during manufacture, for example in a pressing operation.

One process for attaching the plates is illustrated in figures 3A-3D. The steel plates (2) are placed in a brick mould box (6) and positioned against side walls (7). Refractory material (8) is then added to the mould box (6). Anchors (9) projecting from the metal plates (2) extend into the refractory material (8). Pressing of the refractory material (8) is then completed using a top die plate ( 10). After pressing the anchors (9) are anchored into the main body of the brick (3) thereby fixing the plates (2) to the surfaces of the bricks.

These anchors (9) may be formed by punching small holes (13) in the steel plates (2). Punching holes in the steel plates results in steel projecting from the holes, in some instances, up to approximately 3~5mm. The steel plates (2) may also contain a foot ( 1 1 ) by bending a short length at right angles to the main part of the plate.

This foot (1 1 ) assists in pressing by allowing the steel plate (2) to sit on the bottom die plate (12) before the refractory material (8) is added and compacted by the top die plate. During pressing of the bricks the refractory material (8) is compacted around the anchors (9) thereby fixing the plate to the refractory surface. The anchors (9) could also be welded onto the steel plates (2). When a refractory lining made from the described refractory bricks (1 ) is preheated, the steel plates on the hot faces of the bricks offer a physical barrier to oxidation. Typically new refractory linings are preheated to prevent rapid cooling and/or solidification of molten metal added to the furnace. For steel, typical preheating temperatures are in the range of approximately 700 deg C to 1200 deg C. At these temperatures the steel plates remain solid and significantly reduce the oxidation of the carbon on the hot face.

In the above described embodiment typically between 2 and 8 anchors are required to fix plates with dimensions up to approximately 200mm x 300mm. Other embodiment may have only a single anchor or alternatively the plates may be fixed by other methods onto the main body of the bricks.

After preheating, when molten metal is added for the first time, the steel plates attached to the hot face usually melt and become part of the liquid metal or slag. Protection from oxidation may thereafter be provided by the melt. Steel plates fixed to the back face of the refractory remain in place for the life of the lining and provide ongoing protection from oxidation. When the furnace or ladle is emptied, a low permeability layer of metal or slag is often left behind on the hot surface to prevent oxidation until the next use.

Figure 5 shows refractory bricks with metal covers attached after being heated to 1 100°C and being held for 4 hours. The images show how there is minimal oxidation of the area protected by the steel sheets, whilst there is significant oxidation of the area surrounding the steel sheets.

It will be appreciated that the present invention is not limited to steel furnaces and the use of steel protective plates. Other metals, such as iron, may be used as long as the melting point is such that the metal plates do not melt away during preheating of the furnace. Furthermore metal covers other than plates may be used, such as, for example, a metal coating. In addition the present invention is not limited to carbon containing refractories and may be utilised in other refractories prone to oxidation.

An alternate embodiment has a metal cover positioned and affixed to at least a portion of the hot and/or cold face of the refractory lining. In this embodiment a single metal cover can spread over a plurality of bricks rather than only being attached to, and covering, a single refractory brick.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as, an acknowledgement or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Finally, it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.

Claims

The claims denning the invention are as follows:

1. A refractory brick for lining a metal making furnace, ladle or the like, the refractory brick including: a main body with an exposed face, the exposed face being a surface of the refractory brick that is exposed to oxygen when the refractory brick is part of a refractory lining; and a metal cover affixed to the main body, the metal cover at least partly covering the exposed face.

2. A refractory brick as claimed in claim 1 , wherein the oxygen is from heated and/or surrounding air.

3. A refractory brick as claimed in claim 1 or 2 wherein the metal cover has at least one anchor for affixing the metal cover to the main body.

4. A refractory brick as claimed in any one of the preceding claims wherein the anchor is a projection formed by punching a hole in the metal cover.

5. A refractory brick as claimed in any one of the preceding claims wherein the metal cover extends from the exposed face to an adjacent face, and at least partly covers the adjacent face.

6. A refractory brick as claimed in any one of the preceding claims wherein the main body is formed of a ceramic material.

7. A refractory brick as claimed in any one of the preceding claims wherein the metal cover is a metal plate.

8. A refractory brick as claimed in any one of the preceding claims wherein the metal plate is made from steel.

9. A refractory brick as claimed in any one of the preceding claims wherein the exposed face is the surface that forms part of the hot face of the refractory lining.

10. A refractory brick as claimed in any one of claims 1 to 8 wherein the exposed face is the surface that forms part of the cold face of the refractory lining.

1 1 . A refractory brick as claimed in claim 1 . wherein the refractory brick further includes: a second exposed face; and a second metal cover affixed to the main body, the second metal cover at least partly covering the second exposed face.

12. A refractory lining for a metal making furnace, ladle or the like, the refractory lining including a plurality of the refractory bricks according to any one of claims 1 to 1 1 .

13. A refractory lining for a metal making furnace, ladle or the like, the refractory lining including a metal cover attached to the hot and/or cold face of the refractory lining, such that a substantial portion of the hot and/or cold face of the refractory lining is covered by the metal cover.

14. A refractory lining as claimed in claim 13 formed from a plurality of refractory bricks.

15. A refractory lining as claimed in claims 12 to 14 wherein the metal cover is a steel plate.

16. A method for reducing oxidation at the hot and/or cold face of a refractory lining formed of a plurality of refractory bricks, the method including securely positioning one or more metal covers on one or more exposed faces of the refractory bricks, the exposed faces being those faces of the bricks that form part of the hot and/or cold face of the refractory lining.

1 7. A method as claimed in claim 16 wherein the metal cover is a steel plate.

1 8. A method for affixing a metal plate to a refractory brick, the method including the steps of: punching holes in the metal plate such that projecting anchors are formed in the metal plate; positioning the metal plate in a brick mould; and filling the brick mould with refractory material.

19. A metal, plate for attachment to a refractory brick, the metal plate including an anchor for affixing the metal plate to the refractory brick.

20. A metal plate as claimed in claim 19, wherein the anchor is a projection formed by punching a hole in the metal plate.

21. A metal plate as claimed in claim 19 or 20, having a substantially L-shaped profile.

22. A refractory brick for forming a refractory lining, the refractory brick including a metal cover affixed thereto such that when the refractory brick is part of the refractory lining, the metal cover at least partly covers the hot and/or cold face of the refractory brick.

23. A system for reducing oxidation at the hot and/or cold face of a refractory lining formed of a plurality of refractory bricks, the method including securely positioning one or more metal covers on one or more exposed faces of the refractory bricks, the exposed faces being those faces of the bricks that form part of the hot and/or cold faces of the refractory lining.

24. A refractory brick substantially as herein described with reference to the accompanying figures.

25. A refractory lining substantially as herein described with reference to the accompanying figures.

26. A metal plate substantially as herein described with reference to the accompanying figures.

27. A method for forming a refractory brick substantially as herein described with reference to the accompanying figures.