GB1569970A

GB1569970A - Tundish lining

Info

Publication number: GB1569970A
Application number: GB5201375A
Authority: GB
Original assignee: METALAIDS PROCESSES Ltd
Current assignee: METALAIDS PROCESSES Ltd
Priority date: 1977-03-08
Filing date: 1977-03-08
Publication date: 1980-06-25

Description

(54) IMPROVED TUNDISH LINING (71) We, METALAIDS PROCESSES LIMITED, a British Company, of Spring Lane Trading Estate, Malvern Link, Worcestershire WR14 1AH, England, 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: This invention relates to an expendable tundish lining for use in continuous metal casting processes.

A tundish is a vessel which is customarily interposed between the ladle or other supply of molten metal and the continuous casting moulds, so as to provide a reservoir of molten metal which will flow into the moulds at a controlled rate.

Such tundishes normally consist of a metal casing with a semi-permanent lining of refrac tory bricks jointed with refractory cement.

This semi-permanent lining serves to protect the metal casing from the molten metal and also to conserve heat in the reservoir of molten metal.

The semi-permanent lining may be faced with a coating of castable refractory concrete or refractory paint or even with an expensive semipermanent ceramic lining.

At the end of a continuous casting operation it is normally necessary to carry out extensive repair work to the tundish. The residual "skull" of solid metal and slag must be removed from the inside of the tundish, the tundish nozzles must be replaced, and the semi-permanent lining of refractory brickwork must be laboriously patched. It is also common to preheat the repaired tundish to dry any refractory cement used and/or to reduce the thermal shock to the semi-permanent lining when molten metal is poured into the tundish.

It has already been proposed to reduce the residual skull of metal and slag and to reduce the amount of repair work by providing an additional expendable lining on the inside of the semi-permanent refractory brick lining to protect it from attack, and possibly eliminate the need for preheating the tundish, this additional lining being made up of a set of slabs of refractory material with improved heat-insulating properties. However, it has been found in practice that the time taken to assemble such slabs in the tundish and fill the joints with refractory cement can be so long that the assembly-labour costs added to the cost of the expendable lining slabs themselves largely detract from, or even nullify, the potential saving expected to be achieved by protecting the semi-permanent lining. Furthermore, the gaps between adjacent slabs of the additional expendable lining, despite jointing with refractory cement, can allow molten metal to break through and damage the semipermanent lining.

According to the present invention an expendable tundish lining comprises a one-piece lining of non-fired, heat-insulating, refractory material which can be inserted as a complete unit into a tundish to protect the semi-permanent refractory brick lining of the tundish and conserve heat in the molten metal reservoir in use of the tundish.

The one-piece expendable tundish lining of this invention may be composed of any convenient heat-insulating, refractory mixture used in the metal casting industry, an appropriate mix being selected according to the metal cast after taking into consideratin such factors as heat-insulating properties, refractoriness, resistance to erosion, mechanical strength for transport and fitting, and cost.

The one-piece expendable lining must be suitably shaped to fit readily into the semi-permanent refractory lining of the tundish with which it is to be used, with suitable openings in the region of the outlet nozzles and slag overflow areas, and it may conveniently contain ridges or weirs to minimise the turbulence in the filling zone. In order to resist erosion by the molten metal, it may also incorporate inserts of highly refractory or other penetrationresistant material in the area which, in use of the lining, is impinged by the incoming metal.

The one-piece expendable lining may be designed to be a close fit in the semi-permanent refractory lining of the tundish with which it is to be used, in which case the semi-permanent lining and the one-piece expendable lining must be suitably tapered from top to bottom to enable the expendable lining to be lowered into place. Alternatively, the one piece expendable lining may be designed to fit loosely into the semi-permanent lining, the gap between the inside wall of the semi-permanent lining and the outside wall of the expendable lining being filled with any conveniently available, freeflowing, granular refractory material, for example, crushed firebrick, crushed slag, which can be poured into place. The latter method has the advantages that it can accommodate irregularities in the surface and shape of the semi-permanent refractory lining of the tundish and that it facilitates removal of the spent one-piece expendably lining and residual skull of metal and slag after completion of a casting operation.

Whether the one-piece expendably lining is designed as a close fit, or as a loose fit with a granular refractory filling, the process of removal and replacement is much simpler and much quicker than in the case of a multi-slab assembly. The only refractory cement jointing that may be necessary is at the openings for the casting nozzles and at any edges of the lining exposed to the molten metal such as at overflows.

In the case of large one-piece expendable tundish linings, such as may be required in the continuous casting of steel, it may be necessary to improve the mechanical strength of the onepiece expendable linings by incorporating therein a skeleton of strengthening material, for example in the form of metallic rods, wire or fibre. The expendable lining may also be fitted with metallic rings or loops attached to the strengthening skeleton to facilitate lifting and handling.

In the case of a one-piece expendable tun dish lining that is likely to be subjected to severe erosion and penetration by the molten metal, it can be of advantage to manufacture the lining from the material described and claimed in British Patent Specification No 1,477,463, the coherent paper facing sheet being on the inside of the lining.

One-piece expendable linings may be mould ed or formed by any of the known methods of moulding or forming heat-insulating, refractory mixtures used in the metal casting industry.

Where the heat-insulating properties of the expendable lining are less important than the protection afforded to the semi-permanent refractory lining, it is convenient to use typical foundry moulding or core-making mixtures of refractory materials and cold-setting or stovesetting binders, which can be moulded by any of the conventional methods used in the foundry industry such as hand ramming, pressing, jolting or vibrating. Where it is desirable to embody better heat-insulating properties in the one-piece expendable lining it is preferable to use a refractory mixture incorporating organic and/or inorganic fibres as well as binders, such as are widely used for the production of heatinsulating, refractory linings for ingot moulds.

Such mixtures containing fibres may be conveniently moulded by any of the conventional methods used in the production of heat-insulating, refractory ingot mould linings, for example pressing and vacuum-forming.

The invention will now be described, by way of example, with reference to the drawing accompanying the Provisional specification, in which; Figure 1 is a perspective view of a tundish for use in a continuous steel-casting plant, and Figure 2 is a longitudinal sectional view of the tundish shown in Figure 1.

The tundish shown in the drawing comprises a fabricated steel casing 1 having a semi-permanent, refractory brick lining 2. The incoming molten steel is poured into the tundish at 3 and an overflow is provided at 4. Replaceable refractory outlet nozzles are provided at 5. A one-piece expendable lining 6 made in the manner described hereinafter, is simply lowered into place on the flat base of the semi-permanent, refractory brick lining 2 with the aid of lifting tackle attached to eight lifting rings 7 which are moulded into the expendable lining 6. The lining 6 has two openings 8 over the outlet nozzles 5 and is shaped to conform to the overflow at 4. It also incorporates a thin refractory plate 9 in order to resist erosion in the region where the incoming molten steel impinges on the lining. A space about 25 mm wide between the sides and end of the lining 6 and the brick lining 2 is filled with crushed firebrick 10 in free-flowing, granular form, which is simply poured into position. The ex posed joints 11 between the lining 6 and the outlet nozzles 5 and the exposed joints 12 be tween the end of the ling 6 and the brick lining 2 at the overflow, are sealed with refractory cement.

The repair of a tundish using the one-piece expendable lining 6, including the removal of the residual skull of metal and slag, removal of the debris of the expendable lining, the replace ment of the refractory outlet nozzles 5, a small amount of patching to the brick lining 2 and the fitting of the one piece lining itself, requires an average of only 2-3 man-hours, compared with 5-6 man-hours when an expendable lining is used in the form of an assembly of slabs, and compared with an average of 7-10 man-hours when no expendable lining is used and extensive repairs to the semi-permanent refractory brickwork are necessary.

The one-piece expendable lining itself may be made in the following fashion: A metal mould is constructed in two parts one of which, the inner mould part, conforms to the inner configuration of the one-piece expendable lining, and the other of which, the outer mould part, conforms to its outer configuration.

The surfaces of the mould parts precisely conforming to the surfaces of the one-piece expendable lining are constructed of finely perforated metal having a multiplicity of openings of 3h mm diameter comprising 40% of their total surface areas. These finely perforated surfaces are supported by backings of heavy gauge, expanded flattened steel mesh having 40 mm x 20 mm openings comprising 70% of their total surface area and are further supported by a fabricated metal framework. The inner mould part is further constructed into a vacuum chamber by enclosing the space behind the foraminous area with an impervious metal casing fitted with a valve opening connected to a vacuum pump and vacuum reservoir. The outer mould part is constructed with two openings to permit introduction of the moulding mixture.

A main supporting skeleton for the onepiece expendable lining is constructed from 6 mm diameter steel rod, the main skeleton having one rod conforming to the shape of the upper rim of the one-piece expendable lining and four "ribs" to give support to the sides and bottom of the lining, the upper ends of each rod forming the "ribs" being extended in the shape of a loop to form lifting rings. The "ribs" are spot-welded to the rod supporting the rim of the lining.

The main supporting skeleton is placed in position in the outer mould part and a fireclay brick, 300 mm square and 15 mm thick, is placed in position on that part of the inner mould surface corresponding to the area of the one-piece expendable lining on which in use of the lining, the incoming molten steel will impinge. Additional strengthening of steel wire mesh is placed in position to form a. secondary supporting skeleton for the whole of the shape of the one-piece expendable lining. The mould is completed by placing the inner mould part into position, clamping the two parts together, inverting them so that the inner mould part forming the vacuum chamber is underneath, and connecting it to the vacuum pump and reservoir.

A heat-insulating, refractory moulding mixture consisting (by weight) of 80 parts of crushed firebrick granules having a particle size of 1 1A mm or less, 5 parts of phenolic resin, 5 parts of ball clay and 10 parts of slag-wool fibres is made into a slurry by incorporation into 60 parts of water.

Sufficient of the moulding mixture is introduced through the openings in the outer mould part to flow round the supporting skeleton of steel rod and wire mesh and fill the space between the finely perforated surfaces of the mould walls. The vacuum chamber is then evacuated to extract the greater part of the water and leave a layer of moulding mixture on the inner mould surfaces in the form of a wet, but firm, felt-like deposit. More moulding mixture is introduced and the process is repeated until the space between the two mould parts is filled with wet, but firm, felt-like material incorporating the supporting skeleton.

The mould is then inverted, the clamps are removed and the inner mould part is lifted out to leave the wet-formed, one-piece expendable lining deposited on the outer mould part. The moulding mixture is then cut away from the eight lifting rings using a knife. The outer mould part containing the wet-formed, onepiece expendable lining is then placed in a drying stove and dried for 4 hours at 1800C. When the one-piece expendable lining is dry, it is lifted out of the outer mould part with the aid of lifting tackle attached to the lifting rings and is inserted into a transit container for transportation to the tundish repair site.

WHAT WE CLAIM IS: 1. An expendable tundish lining comprising a one-piece lining of non-fired, heat-insulating refractory material which can be inserted as a complete unit into a tundish to protect the semi-permanent refractory brick lining of the tundish and conserve heat in the molten metal reservoir in use of the tundish.

2. A tundish lining as claimed in Claim 1, comprising at least one insert of highly refractory material, or other material resistant to metal penetration, in an area of the lining which, in use of the lining, is impinged by the incoming metal.

3. A tundish lining as claimed in Claim 1 or 2, having incorporated therein a skeleton of strengthening material.

4. A tundish lining as claimed in Claim 3, in which the strengthening material comprises rods, wires or fibres of metallic material.

5. A tundish lining as claimed in Claim 3 or 4, in which metallic rings or loops are attached to the strengthening skeleton to facilitate lifting and handling of the lining.

6. A tundish lining as claimed in any of the preceding claims, in which the lining is made from the material claimed in Specification No.

1,477,463.

7. An expendable tundish lining constructed and arranged substantially as herein described with reference to, and as illustrated in, the drawing accompanying the Provisional specification.

8. A method of lining a tundish with an expendable lining as claimed in any of the

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. an average of only 2-3 man-hours, compared with 5-6 man-hours when an expendable lining is used in the form of an assembly of slabs, and compared with an average of 7-10 man-hours when no expendable lining is used and extensive repairs to the semi-permanent refractory brickwork are necessary. The one-piece expendable lining itself may be made in the following fashion: A metal mould is constructed in two parts one of which, the inner mould part, conforms to the inner configuration of the one-piece expendable lining, and the other of which, the outer mould part, conforms to its outer configuration. The surfaces of the mould parts precisely conforming to the surfaces of the one-piece expendable lining are constructed of finely perforated metal having a multiplicity of openings of 3h mm diameter comprising 40% of their total surface areas. These finely perforated surfaces are supported by backings of heavy gauge, expanded flattened steel mesh having 40 mm x 20 mm openings comprising 70% of their total surface area and are further supported by a fabricated metal framework. The inner mould part is further constructed into a vacuum chamber by enclosing the space behind the foraminous area with an impervious metal casing fitted with a valve opening connected to a vacuum pump and vacuum reservoir. The outer mould part is constructed with two openings to permit introduction of the moulding mixture. A main supporting skeleton for the onepiece expendable lining is constructed from 6 mm diameter steel rod, the main skeleton having one rod conforming to the shape of the upper rim of the one-piece expendable lining and four "ribs" to give support to the sides and bottom of the lining, the upper ends of each rod forming the "ribs" being extended in the shape of a loop to form lifting rings. The "ribs" are spot-welded to the rod supporting the rim of the lining. The main supporting skeleton is placed in position in the outer mould part and a fireclay brick, 300 mm square and 15 mm thick, is placed in position on that part of the inner mould surface corresponding to the area of the one-piece expendable lining on which in use of the lining, the incoming molten steel will impinge. Additional strengthening of steel wire mesh is placed in position to form a. secondary supporting skeleton for the whole of the shape of the one-piece expendable lining. The mould is completed by placing the inner mould part into position, clamping the two parts together, inverting them so that the inner mould part forming the vacuum chamber is underneath, and connecting it to the vacuum pump and reservoir. A heat-insulating, refractory moulding mixture consisting (by weight) of 80 parts of crushed firebrick granules having a particle size of 1 1A mm or less, 5 parts of phenolic resin, 5 parts of ball clay and 10 parts of slag-wool fibres is made into a slurry by incorporation into 60 parts of water. Sufficient of the moulding mixture is introduced through the openings in the outer mould part to flow round the supporting skeleton of steel rod and wire mesh and fill the space between the finely perforated surfaces of the mould walls. The vacuum chamber is then evacuated to extract the greater part of the water and leave a layer of moulding mixture on the inner mould surfaces in the form of a wet, but firm, felt-like deposit. More moulding mixture is introduced and the process is repeated until the space between the two mould parts is filled with wet, but firm, felt-like material incorporating the supporting skeleton. The mould is then inverted, the clamps are removed and the inner mould part is lifted out to leave the wet-formed, one-piece expendable lining deposited on the outer mould part. The moulding mixture is then cut away from the eight lifting rings using a knife. The outer mould part containing the wet-formed, onepiece expendable lining is then placed in a drying stove and dried for 4 hours at 1800C. When the one-piece expendable lining is dry, it is lifted out of the outer mould part with the aid of lifting tackle attached to the lifting rings and is inserted into a transit container for transportation to the tundish repair site. WHAT WE CLAIM IS:

1. An expendable tundish lining comprising a one-piece lining of non-fired, heat-insulating refractory material which can be inserted as a complete unit into a tundish to protect the semi-permanent refractory brick lining of the tundish and conserve heat in the molten metal reservoir in use of the tundish.

1,477,463.

preceding claims, comprising the steps of shaping the outside of the expendable lining to conform substantially to the inner surface of the semi-permanent lining of the tundish, placing the expendable lining in the tundish and forming ajointing of refractory cement between the expendable lining and the semi-permanent lining at the opening or openings in the latter for the casting nozzle or nozzles and at any edge of the expendable lining which is exposed to molten metal in use of the tundish.

9. A method of lining a tundish with an expendable lining as claimed in any of Claims 1 to 7, comprising the steps of shaping the outside of the expendable lining so that when the expendable lining is placed in the tundish there are gaps between the outside of the expendable lining and at least parts of the inner surfaces of the semi-permanent lining on the side walls of the tundish, placing the expendable lining in the tundish, filling said gaps with a free-flowing, granular refractory material, and forming a jointing of refractory cement between the expendable lining and the semi-permanent lining at the opening or openings in the latter for the casting nozzle or nozzles and at any edge of the expendable lining which is exposed to molten metal in use of the tundish.