GB2091399A - Tundish pouring apparatus and method of use - Google Patents

Abstract

The invention provides tundish metal pouring apparatus including a tundish (4) having a plurality of outlet ports in the base thereof; an elongate refractory chimney protruding upwardly from and sealed to each outlet port, said chimney being in two separable parts (9, 10), the separation (11) being transverse to the axis of the chimney shortly above the outlet port. A pouring tube (13) is located beneath each outlet port and protrudes downwardly towards a continuous casting mould. The pouring tube is carried by a member so that it may be held in sealing engagement with the outlet port, or held away from its associated outlet port. Burner means associated with each pouring tube is provided for heating the pouring tube from the bottom thereof whilst the pouring tube is held away from the outlet port. After heating the pouring tube is sealed against the outlet port and metal flow is initiated by removal of the upper part (10) of the refractory chimney. <IMAGE>

Description

SPECIFICATION Improvements in or relating to tundish pouring apparatus and methods This invention relates to tundish pouring apparatus and methods.

A long-standing and continuing series of problems in the technology of continuous casting of metal such as steel surrounds the procedure for transferring hot metal from a ladle to a tundish and thence on to a plurality of continuous casting moulds located below outlet ports in the base of the tundish.

In particular problems arise at the commencement of pouring and at termination of pouring. Such problems, especially at the commencement of pouring, are frequently associated with difficulties arising from temperature loss of the liquid metal in one or more parts of the apparatus tending to cause solidification of the metal and hence blockage of the metal flow.

It is an object of the present invention to overcome or at least substantially reduce at least some of thes problems.

According to one aspect of the invention there is provided tundish metal pouring apparatus including a tundish having a plurality of outlet ports in the base thereof; an elongate refractory chimney protruding upwardly from and sealed to each outlet port, said chimney being in two separable parts, the separation being transverse to the axis of the chimney shortly above the outlet port; a pouring tube located beneath each outlet port and protruding downwardly towards or into a continuous casting mould, said pouring tube being carried by a member adapted to urge the pouring tube into sealing engagement with the outlet port; means for holding the pouring tube away from its associated outlet port; and burner means associated with each pouring tube and capable of heating the pouring tube from the bottom thereof together with its associated outlet port whilst the pouring tube is held separate from the outlet port associated therewith.

According to another aspect of the present invention there is provided a method of initiating tundish metal pouring comprising the steps of sealing a two-part refractory chimney to each outlet port in the base of the tundish so that it protrudes upwardly from the outlet port of the tundish; locating a pouring tube beneath each outlet port projecting downwardly towards or into an associated continuous casting mould, said pouring tube being held apart from the outlet port; preheating each pouring tube and its associated outlet port by directing a burner through each tube from the bottom thereof; terminating the preheating of each pouring tube, bringing each preheated tube into sealing location against the bottom of its associated preheated outlet port; pouring hot metal into the tundish to a level above the joint between the two parts of each refractory chimney; and removing the upper part of each refractory chimney so that hot liquid metal flows through the lower part of each refractory chimney, outlet port and pouring tube into the continuous casting mould located therebeneath.

The arrangement described hereinabove is especially advantageous in that it enables a continuous casting machine, such as an eightstrand bloom casting machine for example, to operate with pouring tubes whilst at the same time retaining the advantageous feature of metering nozzles disposed in the outlet ports. In any emergency the pouring tubes can be easily removed and molten metal halted by sealing the nozzle bore from below by means of copper or steel plug without causing difficulties for the casting machine.

The arrangement defined overcomes the practical difficulties of initiating steel flow through the metering nozzles and pouring tubes whilst retaining the advantages of cold tundish practice.

The use of overhead stoppering control is completely avoided.

Hitherto when casting with metering nozzles, the bores of the nozzles have had to be opened by lancing with oxygen to start the flow. Frequently having initiated steel flow, further lancing has proved to be necessary to restart (should the steel freeze) or to trim away build-up of solidified steel around the lower lip of the bore of the metering nozzle.

With a pouring tube in position below the metering nozzle there is no access to the nozzle.

However by means of the refractory chimneys and preheating of the pouring tubes and nozzles steel flow from the tundish can be initiated at will.

The refractory chimneys are located above each outlet port in the tundish such that their open tops are higher than the maximum steel level in the tundish. It is necessary that the chimneys are sealed above the outlet ports against the ingress of liquid steel to prevent the contact of steel with the nozzles and possible freezing before the desired initiating time.

In practice the tundish will be filled to operating level as rapidly as possible, and since the chimneys will at such time be in position, no steel enters the outlet ports during filling. When the operating level in the tundish has been reached the upper portion of each chimney is pulled away in any required operational sequence. Long rods may be used for this purpose by operators located adjacent the end of the tundish.

It is to be noted that the top part only of the chimney is removed when initiating flow, so that cooler molten steel from adjacent the floor of the tundish does not enter the nozzle (which might result in solidification) and that steel flowing into the nozzle is from a level well above the floor of the tundish. The very rapid flow of steel upon removal of the top portion of the chimney, together with the substantial preheating of the pouring tubes and metering nozzles allows the molten steel to flow easily through the outlet system without any tendency to solidify.

The preheating may be provided by oxygenpropane burners, adapted to preheat both the pouring tube and the metering nozzle at the same time. The lowering of the upper end of the pouring tube from the outlet nozzle during preheating is essential to provide adequate flow of the heating i gases up the pouring tube onto the metering nozzle. Thus it is to be noted that metering nozzles have a relatively small bore which would not allow adequate flow therethrough of the heating medium. Separation of the pouring tube from the ) outlet port provides an appropriate gap for flow of this medium.

The pouring tube may be carried in a fork mounted at one end of a steel arm which in turn may be mounted by means of a trunnion on a bracket carried by the tundish. The upper end of the pouring tube may be held, in the pouring condition, against a ceramic fibre sealing gasket around the underside of the outlet port, by counterweights carried on the steel arm on the other side of the trunnion mount from the pouring tube. By such an arrangement the pouring tube may be swung away from the outlet port should it be necessary to stop flow of liquid steel, which can then be accomplished in the usual way by plugging from below.

In order that the invention may be more readily understood one embodiment thereof will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a sectional elevation of parts of a tundish outlet including features of the present invention; Figure 2 is an above plan view of a tundish also showing features of the present invention; and Figure 3 is an isometric view showing a portion below the floor of the tundish again including features of the present invention.

As will be seen from the drawings the tundish 1 is provided with four outlet ports 2 equispaced along its length. In the usual way an impact area 3 is provided for reception of molten steel poured from a ladle (not shown) located above the tundish. The tundish is, of course, a composite structure comprising a steel shell 4, a compacted refractory liner 5, and a tiled inner surface 6. At each outlet port is an annular refractory outlet block 7 within which is located a conical metering nozzle 8. Tightly rammed above each metering nozzle is a refractory two-part chimney 9 and 10 jointed with cement as shown as 11. Disposed around the lower tip of the metering nozzle 8 and cemented against the block 7 is a ceramic fibre sealing gasket 12 against which is urged, in pouring usage of the assembly, a below-tundish pouring tube 13.

The pouring tube 1 3 is urged upwardly against the sealing gasket by means of a counterweighted lever arrangement 14 comprising a pivoting fork 1 5 carrying the tube mounted on the end of a tubular steel arm 16. The tubular steel arm 1 6 is in turn carried by means of a trunnion 17 mounted on a bracket 1 8 carried by the tundish. The end 1 9 of the arm remote from the pouring tube 13 carries a weight 20 sufficient to force the upper end of the pouring tube into sealing contact with the gasket 12. Each pouring tube 1 3 is provided with insulating sleeves 21 and in use the lower end protrudes below the level of molten metal 22 in a mould 23 of the continuous casting machine.

An oxygen-propane burner 24 is provided for each of the pouring tubes 13 to provide preheating by injecting heating gases into the bottom end 25 of the pouring tube 1 3 (there being no metal in the mould of the continuous casting machine at that time), up the pouring tube and into the lower end of the metering nozzle 8. In this preheating condition, in order to provide adequate flow of the heating medium, the upper end 26 of the pouring tube is held away from the sealing gasket by means of a spacing device 27 bearing on the underside of the tundish. It will be appreciated that in the drawings (Fig. 3) the burner 24 is not illustrated in its operating disposition.

For initiating steel pouring the preheating burner 24 is withdrawn from the continuous casting moulds, the spacer devices 27 are reorientated to allow the pouring tube 1 3 to seat in a sealing fashion against the refractory sealing gasket 12.

Steel is poured into the impact area of the tundish 1 from a ladle until the metal in the tundish reaches the desired operating level. The upper portions 10 of each of the four refractory chimneys are then broken away by means of elongate rods 28 from the end of the tundish.

Hot steel now pours at the appropriate metered rate through each of the metering nozzles 8 into the pouring tube 13 located therebelow and thence into the continuous casting mould 23.

By means of the invention as particularly described hereinabove we have provided an arrangement which overcomes the difficulties of initiating steel flow through metering nozzles whilst retaining the advantages of cold tundish operating practice. It is to be observed that difficult and costly overhead stoppering devices are avoided by our invention.

High quality alloy rail grades of steel, for example, can be successfully produced with very low rejection levels, the use of pouring tubes enabling greater metallurgical control of the process and reducing very considerably, subsurface blow holes in the continuous-cast bloom produced.

It is also to be observed that by means of the invention it is possible to continuously cast steels (having no aluminium) inexpensively and simply such as certain rail steels and high-tensile wire steels which would otherwise require the aforementioned stoppering control and usually require aluminium additions to prevent refractory erosion.

Claims (8)

1. Tundish metal pouring apparatus including a tundish having a plurality of outlet ports in the base thereof; an elongate refractory chimney protruding upwardly from and sealed to each outlet port, said chimney being in two separable parts, the separation being transverse to the axis of the chimney shortly above the outlet port; a pouring tube located beneath each outlet port and protruding downwardly towards or into a continuous casting mould, said pouring tube being carried by a member adapted to urge the pouring tube into sealing engagement with the outlet port; means for holding the pouring tube away from its associated outlet port; and burner means associated with each pouring tube and capable of heating the pouring tube from the bottom thereof together with its associated outlet port whilst the pouring tube is held separate from the outlet port associated therewith.

2. Apparatus according to Claim 1 wherein the burner means comprises an oxygen-propane burner arranged to preheat the pouring tube and the outlet port at the same time.

3. Apparatus according to Claim 1 or 2 wherein the outlet port includes a metering nozzle.

4. Apparatus according to any one of the preceding claims wherein the pouring tube is carried in a fork mounted at one end of a steel arm supported by means of a trunnion on a bracket carried by the tundish.

5. Apparatus according to Claim 4 wherein the upper end of the pouring tube is held, in the pouring condition, against a ceramic fibre sealing gasket around the underside of the outlet port by counterweights carried on the steel arm on the other side of the trunnion mount from the pouring tube.

6. A method of initiating tundish metal pouring comprising the steps of sealing a two-part refractory chimney to each outlet port in the base of the tundish so that it protrudes upwardly from the outlet port of the tundish; locating a pouring tube beneath each outlet port projecting downwardly towards or into an associated continuous casting mould, said pouring tube being held apart from the outlet port; preheating each pouring tube and its associated outlet port by directing a burner through each tube from the bottom thereof; terminating the preheating of each pouring tube, bringing each preheated tube into sealing location against the bottom of its associated preheated outlet port; pouring hot metal into the tundish to a level above the joint between the two parts of each refractory chimney; and removing the upper part of each refractory chimney so that hot liquid metal flows through the lower part of each refractory chimney, outlet port and pouring tube into the continuous casting mould located therebeneath.

7. Tundish metal pouring apparatus substantially as shown in and as hereinbefore described with reference to the accompanying drawings.

8. A method of initiating tundish metal pouring substantially as hereinbefore described with reference to the accompanying drawings.