GB2068515A

GB2068515A - Porous Plugs in Metallurgical Vessels

Info

Publication number: GB2068515A
Application number: GB8100351A
Authority: GB
Original assignee: Foseco Trading AG
Current assignee: Foseco Trading AG
Priority date: 1980-01-31
Filing date: 1981-01-07
Publication date: 1981-08-12
Also published as: GB2068515B

Abstract

A metallurgical vessel e.g. ladle having a gas-permeable plug (4) in an inlet in a wall for passage of a treatment agent e.g. a gas to the interior of the vessel has a preformed cover (7) of a gas-permeable, refractory, heat-insulating composition over the face of the plug exposed to the interior of the vessel. The cover (7) is to prolong the life of the plug (4). <IMAGE>

Description

SPECIFICATION Porous Plugs n Metallurgical Vessels The invention relates to metallurgical vessels and in particular to vessels which have an inlet for a treatment agent, in the form of a gas or carried by a gas, for treatment of molten metal in the vessel.

Such a vessel has in one wall, often the floor, an inlet for the gas, the inlet containing a porous plug through which the gas is passed. Typically the porous plug is formed of a material such as fused mullite, sintered alumina or corundum. These materials are, however, expensive and while steps are taken to protect the exposed face of the porous plug from the erosive attack of the molten metal such steps are not very effective. As a result the costly porous plug needs to be replaced frequently. It is an object of this invention to prolong the life of a porous plug as well as conferring other advantages.

According to the invention a metallurgical vessel has an inlet in a wall for the passage of a treatment agent to the interior of the vessel, a gas-permeable plug being located in the inlet, the face of the plug exposed to the interior of the vessel being covered by a preformed cover of a gas-permeable, refractory, heat-insulating composition.

The cover may take the form of a suitably sized and shaped slab. The cover may also be in the form of a cap having a cover for the face of the plug and extending into the inlet in the vessel wall.

The gas-permeable cover may be formed of refractory filler, organic and/or refractory fibre and a binder. The filler may be silica, alumina, magnesia or a refractory silicate; the fibre may be asbestos, calcium silicate fibre, aluminosilicate fibre or paper; and the binder may be a colloidal silica sol, sodium silicate, starch, phenol-formaldehyde resin or urea-formaldehyde resin. The permeability may be adjusted to an appropriate level by adjusting the density and/or fibre content of the cover. Adjustment of the particle size of the filler is a particularly satisfactory way of adjusting the permeability, an increase in particle size yielding an increase in permeability. The cover is preferably formed by dewatering an aqueous slurry of the ingredients in a suitably shaped former and drying the shaped product and causing or allowing the binder to set.

The vessel may be a tundish or ladle and the plug may be in a floor- or side-wall.

In order that the invention may be better understood it will now be described by way of example with reference to the accompanying diagrammatic drawings, in which Figure 1 is a sectional view of part of the floor of one ladle, and Figure 2 is a partial sectional view as in Figure 1 of another ladle.

The ladle of Figure 1 has an outer metal wall 1 above which are two layers of refractory bricks 2.

A nest brick made up of two super-imposed bricks 3A, 3B, is set in the floor. The nest houses a porous plug 4 set on a base brick 5. The basebrick 5 has a central bore through which passes a gas pipeline 6 connected to a nitrogen or argon gas cylinder, not shown. The porous plug 4 is formed of fused mullite or the like, and is of conical shape and is slightly smaller than the cavity of the upper nest brick 3A. The gap is filled by a conical cap 7 made of a gas-permeable, refractory, heat-insulating composition such as those in the following Table.

% by weight ofingredient Ingredient Composition 1 Composition2 Composition3 silica flour - 23.5 70.5 silica sand 94 70.5 23.5 paper 3 3 3 P-F resin 2 2 2 U-F resin 1 1 1 Permeability (A.F.S. units) 49 18 3 The above compositions were formed into the desired shape by the method already described and in each case the product had adequate resistance to moving molten steel. As can be seen from the Table, the permeability decreases as the relatively fine silica flour is incorporated at the expense of the relatively coarse silica sand.

In use, gas is passed up the pipeline 6 and through the plug 4 and the cap 7 into molten steel.

contained in the ladle. The cap 7 protects the face of the plug 4 which would otherwise be in contact with the molten steel. At the end of treatment the ladle is emptied and the cap 7 prevents any residual steel from solidifying on the plug 4. When the ladle is empty the cap is reduced to a powder which is brushed away, the plug 4 is then cleaned and a fresh cap 7 is set in position. With time the plug 4 becomes worn and any gaps formed may allow molten steel into the nest to do damage but a larger cap 7 may be used to fill the enlarged gap so reducing this risk. In this way the life of the costly plug 4 is prolonged.

In the embodiment of Figure 2 the cap 7 is replaced by a slab 8 of a gas-permeable composition as specified above and this simply sits on top of the plug 4. (Where the porous plug 4 is set in a vertical wall of the ladle the slab 8 is secured thereto by mortar or a mechanical fixing device). Other slabs 9, 10 of the same or different chemical composition may also be present at the sides of the slab 8 and the slabs 8, 9, 10 may be integrally formed.

Claims

1. A metallurgical vessel having an inlet in a wall for the passage of a treatment agent to the interior of the vessel, a gas permeable plug being located in the inlet, characterised in that the face of the plug exposed to the interior of the vessel is covered by a preformed cover of a gas-permeable, refractory, heat-insulating composition.

2. A vessel according to claim 1 characterised in that the preformed cover comprises refractory filler, organic and/or refractory fibre and a binder.

3. A vessel according to claim 2 in which the preformed cover has been formed by dewatering an aqueous slurry of the ingredients in a former, drying the resultant shaped product and causing or allowing the binder to set.

4. A vessel according to claim 1 substantially as described herein with reference to the accompanying drawings.