The invention relates to an insert for vessels containing molten metal, such as e.g. tapping conduits, discharge areas, distributors and the like, particularly, however, continuous casting ingot moulds for steel.

It has been common practice in the continuous casting of steel to fill the molten steel from above into a water-cooled copper ingot. The ingot is oscillated longitudinally in order to prevent the solidifying steel from adhering to the surface of the ingot mould. But even this measure can never guarantee the absence of defects in the solidified steel which must be removed by means of a specific operation in order to avoid that these defects produce a detrimental effect in the processed material. Similarly, casting powder residues show at the outer surface of the solidified steel, which must be removed by flame descaling before rolling the solidified material.

In view of the high stresses to which the ingot mould is exposed, so far ceramic materials, in particular oxide-ceramic materials, have been used. These materials must exhibit a certain amount of heat- conductivity in order to be able to perform the solidi¬ fication process in the solidification area of the ingot mould since only the heat discharge in the

cooling operation can ensure that, on the one hand, the steel solidifies and, on the other hand, the lining material of the ingot mould is not overstrained.

The present invention particularly deals with the problem to provide a continuous casting ingot mould for steel with an insert of an appropriate material, so that the solidified steel block can be rolled without any further operations. In addition, the invention deals with inserts to be placed in vessels or conduits containing liquid metal, for instance, tapping conduits, discharge areas, distributors and the like.

According to the invention the insert is characterised in that it is an annular part which fits into a corresponding inner recess in the solidification region in the vessel (e.g. continuous casting ingot mould) with flush aligned inner surface and that it comprises a material of high melting point which in interaction with the molten metal (steel) has a very large wetting angle. The melting point of the insert must be sufficiently high, of course, to withstand molten steel and slag.

With the selected material it can be achieved that the wetting angle of steel and slag is clearly above 90"C and may be, for example, from 110 ^* C to 140 ^* C and might even approach as high as 150 ^β C to 155 ^β C. The steel or the slag acts as wetting liquid, this resulting in significant advantages in that due to the insignificant wetting, a sliding effect is produced causing the liquid metal to slide readily down the

walls of the ingot mould so that it is no longer necessary to jolt the ingot moulds or to subject them to other oscillations.

In addition, due to the insignificant surface wetting of the steel at the inner surface of the ingot mould, the action, in particular the erosion, on the lining material of the ingot mould is much smaller. In this context one could also speak of a non-wearing material, so that extended service life can be achieved.

It may also be possible to dispense with the use of casting powder so that the solidified material neither exhibits casting powder residues nor so-called oscillation marks so that no flame descaling is necessary for material to be rolled.

Preferred materials for the insert are carbides, borides, nitrides or mixtures thereof or mixtures of one or more of these with ceramic oxides.

These materials are materials which have a relatively large wetting angle, which is due to their crystal lattice structure.

For achieving the advantageous effects by means of the insert according to the invention it is not necessary to use only these materials for the insert. The effect is also produced with a relatively modified form, if the above-mentioned materials are added to the material for the insert.

According to the invention boron nitride, silicon carbide, aluminium nitride and zirconium boride are particularly preferred.

The insert may be made by hot pressing or isostatic pressing, by hot-pressure sintering or sintering with addition of suitable sintering aids to the composition of the insert.

In the following, the invention is explained by way of example with reference to the drawing, which is a cross-sectional view through a continuous casting ingot mould for steel.

Reference numeral 10 designates the continuous casting ingot mould. Said ingot mould substantially has the shape of a hollow cylinder, with cooling conduits (not shown) being provided in the walls for achieving the desired heat discharge.

12 designates a casting powder depositing above the solidfying steel 11.

In the solidification area an annular- cylindrical insert 20 is provided which consists of an appropriate material as, for example, indicated above.

The insert 20 is designed to align with the inner surface (21) of the ingot mould 10, and as it hardly wears due to its properties, this ideal

configuration in respect of the casting procedure may be maintained for the entire service life of the ingot mould.

The insert 20 which is inserted into the ingot mould 10, can be made to be exchangeable and it can also be incorporated into the inner walls of the ingot mould 10 in the form of lining material. According to the invention the insert 20 is an independent and self- supporting individual unit which may be introduced into the ingot mould from above. The insert 20 may also be made of a plurality of individual segments.

It is also possible to advance the cooling effect right up to the outer surface of the insert 20 so that a still more effective discharge of heat becomes possible.