GB1597850A - Electric arc furnace roofs - Google Patents

Description

(54) ELECTRIC ARC FURNACE ROOFS (71) We, VEITSCHER MAGNESIT WERKE-ACTIEN-GESELLSCHAFT a company organised under the laws of Austria, of Schubertring 10--12, A 1010 Wein, Austria, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention concerns a surround for an aperture in the roof of an electric arc furnace consisting of a collar of refractory wedge bricks and a body of refractory tamping clay disposed in the space between this brick collar and the brickwork of the roof.

According to earlier techniques apertures in the roofs of electric arc furnaces were walled in only with bricks, and for this a multiplicity of differently shaped bricks was required, and these bricks were mostly produced by hand-shaping. The development and production of serviceable tamping clays now permits quicker and more economical formation of aperture collars with a few simple brick shapes, the attachment of the aperture collar to the surrounding roof brickwork being effected by a tamped body of tamping clay. With many apertures, e.g. apertures for electrodes, the aperture collar is inserted into the roof arch not radially but so that wedges of clay occur that diverge downwards, which entails the risk that such portions of clay will fall in and lead to collapse of the aperture surround.

In order to offset this risk, collar bricks have been provided with variously designed grooves in their backs, i.e. in the surfaces directed towards the clay. These grooves of course serve to keep the clay body in the roof assembly and to prevent the bricks from slipping through to the interior; however, as shown by experience, they suffer from a great drawback: the grooves, no matter how flat and smooth they are made, constitute notches. Owing to the notch effect the bricks, especially those of basic material, are fractured in rapid succession in each "groove valley", i.e. at their weakest points, and the fragments drop off. The progressive brick erosion thus caused is in practice so severe that the roofs must be frequently repaired.

The present invention provides an electric arc furnace having in its roof brickwork an aperture surrounded by a collar of refractory wedge bricks and a body of refractory tamping clay disposed in the space between this brick collar and the roof brickwork, an internal reinforcement surrounding the brick collar being located in the tamped body. The tamping clay surrounding the brick collar forms a monolithic block with the reinforcement, so that no portions of clay can loosen and drop out.

The invention is illustrated in more detail in the accompanying drawing in which: Figure 1 shows, in vertical section; an aperture surround and the adjacent roof brickwork of an electric arc furnace; Figure 2 shows the corresponding plan view; and Figure 3 shows a conventional collar brick is elevation.

The surround of the illustrated roof aperture consists of a brick collar 6 and a tamped body 1 which fills the space between the brick collar 6 and the roof brickwork. As can be seen from Figure 2, the brick collar 6 consists of wedge brick the taper of which is determined by the diameter of the aperture. Figure 1 reveals that the bricks are also wedge-shaped on the outside (the backs of the bricks). The tamped body 1 surrounding the brick collar6 has, in the region 2 liying towards tte centre of the aperture, a negative wedging, i.e. one that diverges downwards, and this can, in prior structures, lead to the falling out of the portions of clay from the region 2.

Therefore, to anchor the tamped body, use has been made of conventional framing bricks as in Figure 3 with grooves 3 on the back. These bricks however readily fracture at their weakest points 4 owing to the notch effect, and the fragments drop off, so that the roof has to be repaired because of brick erosion.

According to the invention the dropping out of portions of clay from the endangered region 2 is prevented by locating in the tamped body 1 an internal reinforcement 5 placed around the brick collar 6. The annular, monolithic clay block thus formed is, outside the region 2, anchored in the roof brickwork by wedge action and carries the endangered region 2 with it.

The internal reinforcement 5 consists of a mat of expanded metal, wire netting, wire grating or similar perforate material which allows clay to penetrate through the mat.

Iron or steel is primarily the material to be considered for this mat, but other metals like aluminium, or a synthetic resin, may also serve. The bricks of the collar 6 can now have smooth backs and so not be subject to the notch effect. If as shown in Figure 1 the bricks are seated in the brickwork in a slightly conical form, slippage towards the interior is prevented with certainty, but application of the invention is also advantageous with bricks having an unwedged rear surface.

WHAT WE CLAIM IS: 1. An electric arc furnace having in its roof brickwork an aperture surrounded by a collar of refractory wedge bricks and a body of refractory tamping clay disposed in the space between this brick collar and the roof brickwork, an internal reinforcement surrounding the brick collar being located in the tamped body.

2. A furnace according to claim 1 wherein the internal reinforcement is of perforate metal or synthetic resin.

3. A furnace according to claim 2 wherein the internal reinforcement is of expanded metal or a netting or grating.

4. An electric arc furnace having a roof aperture with a surround substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawing.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. use has been made of conventional framing bricks as in Figure 3 with grooves 3 on the back. These bricks however readily fracture at their weakest points 4 owing to the notch effect, and the fragments drop off, so that the roof has to be repaired because of brick erosion. According to the invention the dropping out of portions of clay from the endangered region 2 is prevented by locating in the tamped body 1 an internal reinforcement 5 placed around the brick collar 6. The annular, monolithic clay block thus formed is, outside the region 2, anchored in the roof brickwork by wedge action and carries the endangered region 2 with it. The internal reinforcement 5 consists of a mat of expanded metal, wire netting, wire grating or similar perforate material which allows clay to penetrate through the mat. Iron or steel is primarily the material to be considered for this mat, but other metals like aluminium, or a synthetic resin, may also serve. The bricks of the collar 6 can now have smooth backs and so not be subject to the notch effect. If as shown in Figure 1 the bricks are seated in the brickwork in a slightly conical form, slippage towards the interior is prevented with certainty, but application of the invention is also advantageous with bricks having an unwedged rear surface. WHAT WE CLAIM IS:

1. An electric arc furnace having in its roof brickwork an aperture surrounded by a collar of refractory wedge bricks and a body of refractory tamping clay disposed in the space between this brick collar and the roof brickwork, an internal reinforcement surrounding the brick collar being located in the tamped body.

2. A furnace according to claim 1 wherein the internal reinforcement is of perforate metal or synthetic resin.

3. A furnace according to claim 2 wherein the internal reinforcement is of expanded metal or a netting or grating.

4. An electric arc furnace having a roof aperture with a surround substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawing.