GB2037633A - Pouring tube for continuous casting - Google Patents

Abstract

The tube which conveys molten steel in continuous casting from a distributor reservoir to the mould comprises a refractory lining (10) in a metal casing (1, 3) having ribs (5) and a refractory tube (12) the upper end of which is secured within the casing (1, 3), the lower end projecting below the casing and intended to be submerged below the metal surface in the mould. A side spout (6) is provided for insertion of a rod of metal alloying material into the flowing melt stream; the region of penetration of the spout through the lining (10) includes a vault formation (8) and relieved area (9) to minimise metal splashing and accumulation. <IMAGE>

Description

SPECIFICATION A downrunner tube with an alloy addition dosing arrangement, applicable to continuous casting processes The present invention is concerned with downrunner tubes for use ill a distributor reservoir inlet to guide and convey moltcn steel into ingot moulds in continuous casting processes.

The prime purpose of downrunner tribes as are used at the present time in the contintiotis casting process is to prevent the molten metal stream that flows from the distributor reservoir outlet from dropping onto the surface of the molten metal in the ingot mould, thereby making bubbles form inside the molten mass and causing defective ingots to be produced. It is for this reason that the bottom end of the downrunner tube is kept submerged in the molten metal inside the ingot mould, so as thus to prevent any splashing and all kinds of cavities from forming in the inside of ingots manufactured by the continuous casting process.

Up to the present time, however, these downrunner tubes have always been made out of a length of refractory material which required to be removed and replaced every time a pour was made, and this entailed srious maintenance difficulties together with a high cost of the refractory downrunner tube in question, since it was required to be of considerable length.

It was due to this length too that handling of the downrunner tube had to be very carefully performed, because if, while being moved and suitably positioned, it was allowed to knock against any object, it would break easily, since these refractories possess a high fragility index.

Our co-pending British Patent Application No.

20227967848923 relates to the provision with a downrunner at a lower cost, and making it stronger by means of fitting it with a casing that wholly covered it, where the refractory pipe that was to be submerged in the molten metal in the ingot moulds, jutted out at the bottom end. The basic feature of this arrangement is that the inside walls of this casing is lined with a layer of refractory material that prevents same from reaching undesired temperatures, while the bottom was provided with a strengthenerforthe protruding tube.

Moreover, this annular casing is provided with means to enable it to be attached and positioned on the distributor reservoir, so that it may be placed in perfect alignment with the outlet hole through with the molten steel flowed.

When the pour is completed, it is necessary to remove this down runner from the disributor reservoir, in accordance with the usual practice, and because of how the assembly has been made, it is also necessary to exert a considerable force in order to withdraw it from its seating, this operation being performed by percussion, which causes damage and deformations on the casing structure.

The invention provides a downrunnertube arrangement for use in continuous casting processes, including means for introducing an alloying addition into a stream of molten metal passing through the tube, comprising at least one inlet spout for progressive inserticn into the interior of the tube of a rod comprised of metal of the desired alloying constitutents, said spout(s) being provided with a hole having contours adapted to guide the rod and allow it to impinge upon the molten metal stream so as to achieve alloying of the metal in a wholly controlled manner, means being provided to reg slate the rate of feed of the rod(s) of alloying metal.

Advantageously the tube may comprise a metal casing having a refractory lining, said lining being reduced in thickness at regions beneath the spout(s), the hole(s) of which are provided with a vault in the upper surface thereof which is peripheral to the inner circumference of the lining.

Conveniently the casing may be provided with at least one rib for facilitating its handling and ease of dismantling after use.

Hence, the metal case is provided with a number of ribs or reinforcements, which are fully able to withstand such percussion forces, with no damage at all being sustained by the metal casing as a whole, these ribs moreover facilitating its handling and providing the whole assembly with a high degree of ruggedness.

A further feature provided in the down runner tube is that there are sides in same that lead to the molten stream that flows through it, such holes being made through the metal casing as well as its inside refractory lining. In this way, rods of material may be inserted into the holes so that they are immersed in the molten stream in order thus to obtain specific alloys.

The fact that a metal rod is inserted in a molten stream, and since the temperature of such stream is more than sufficient to melt the rod, means that a perfect mix and alloy can be obtained, but here it is to be realised that upon such insertion of the rod in the molten stream, there is splashing and other secondary effects which arise, for which reason it becomes necessary to design the hole in such a way that it has special features so as to avoid all the difficulties which could arise as the result of such impingement or insertion of the rod in the molten stream.

The way this problem is overcome consists in shaping the top of the hole in the refractory lining in the way of a vault which is peripheral to the inner circumference of said lining, so as to prevent the material from clogging and to prevent splashes from building up in this area.

Moreover, the bottom of the hole is made to have a larger degree of concavity, which is to say that there is a reduction in the thickness of the lining, so as to allow the fluidity to be encouraged of any possible deviations of the molten stream in that area.

There will now be described an example of the invention. The description, which is given by way of example only, is intended to be read with reference to the accompanying drawings, in which Figure 1 shows a side elevational view of the downrunner tube partly in cross-section; Figure 2 is an underneath plan view of the downrunner tube showing only one metal rod insertion hole.

A metal casing is provided which is comprised of two halves 1 and 3 so that such two halves can be hinged thereupon and thus facilitate the removal of the refractory lining thereof once this mental casing has been used for a pour, and in order for it to be used again, it is simply necessary to position these two halves suitably and to provide them with an inside refractory lining, whereupon the assembly is ready to be used anew.

The refractory lining 10 on the half-casing 1 does not cover the whole thereof, since a bracket 2 co-operating with the lower part of the half-casing 1 engages directly with and holds the upper part of a downrunner 12 pipe, this being the length which is submerged in the molten metal within the ingot mould.

It may be seen that with this design, a continuous down-runner is achieved, and that the molten metal coming down from the outlet in the distributor reservoir, does not enter into contact with the atmosphere, thus avoiding any presence of bubbles and cavities in the final ingot.

It is also to be noted that the metal casing is provided with feet or lugs 4, the purpose of which is to serve as holders and linking devices between the down runner tube assembly and the distributor reservoir (not shown) where it is to be installed. The casing is furthermore provided with a number of ribs 5, so that percussion blows may be applied thereto as necessary in order to remove the downrunner tube from the distributor reservoir once the pour has been completed, when, as is known, there is tendency to stick and adhere, without the metal casing structure being damaged in the least by such blows.

A single inlet spout 6 is provided, although it will be understood that several spouts may be provided as required, and comprises a hole 7 through which the tip of a rod, made of suitable metal for the alloy to be obtained, is inserted. This rod must be inserted progressively at a predetermined rate, which varies in accordance with the speed of the flow of molten metal from the outlet in the distributor reservoir.

In view of the fact that when the rod is inserted through the hole 7 and impinges upon the molten stream that flows through the downrunner, disturbances are caused that give rise to deflection and splashing in the molten stream, and so in the interest of avoiding any secondary effects therefrom, a vault 8 is provided in the upper surface of the hold, whilst there is a reduction in the thickness 9 of the refractory lining below the hole, in order to increase the cross-section of the tube and improve the flow of the molten stream down into the ingot mold.

Claims (4)

1. A downrunnertube arrangement for use in continuous casting processes, including means for introducing an alloying addition into a stream of molten metal passing through the tube, comprising at least one inlet spout for progressive insertion into the interior of the tube of a rod comprised of metal of the desired alloying constitutents, said spout(s) being provided with a hole having contours adapted to guide the rod and allow it to impinge upon the molten metal stream so as to achieve alloying of the metal in a wholly controlled manner, means being providotl lo regulate the rate of feed of the rod(s) of alloying metal.

2. An arrangement as claimed in claim 1 wherein the tube comprises a metal casing having a refractory lining, said lining being reduced in thickness at regions beneath the spout(s), the hole(s) of which are provided with a vault in the upper surface thereof which is peripheral to the inner circumference of the lining.

3. An arrangement as claimed in either one of claims 1 and 2, wherein the tube comprises a metal casing having a refractory lining and the casing is provided with at least one rib for facilitating its handling and ease of dismantling after use.

4. A downrunnertube arrangement for use in continuous casting processes, constructed and arranged substantially as hereinbefore described with reference to and as shown in the accompanying drawings.