GB2157210A

GB2157210A - Refractory immersion nozzles

Info

Publication number: GB2157210A
Application number: GB08508572A
Authority: GB
Inventors: Heinrich Geller; Hans Liestner; Ortwin Rave
Original assignee: Didier Werke AG
Current assignee: Didier Werke AG
Priority date: 1984-04-03
Filing date: 1985-04-02
Publication date: 1985-10-23
Also published as: GB8508572D0; FR2561957A1; CA1239522A; IL74699A; JPS60213346A; GB2157210B; IL74699A0; FR2561957B1; DE3412388A1; DE3412388C2

Abstract

A refractory immersion nozzle for pouring molten steel into ingot moulds 3 of small cross-section e.g. from a continuous billet casting installation includes a pouring tube 1 of ceramic oxide material, e.g. stabilised ZrO2, at at least that end of the nozzle which, in use, is immersed. A steel shell 4 may be provided. The upstream end of the nozzle may be supported by a refractory concrete flange 2 which may have a conduit 6 therethrough for the supply of gas to a porous liner 5. <IMAGE>

Description

SPECIFICATION Refractory immersion nozzles The invention relates to refractory immersion nozzles, particularly for pouring molten steel into ingot moulds of small cross-section from continuous billet casing installations.

With ingot moulds having a small pouring crosssection, whose sides are less than 125 mm long, conventional immersion nozzles manufactured from conventional refractory materials, for instance, alumina-graphite or vitreous silica, have only a short service life and thus do not permit a continuous pouring operation thereby rendering the pouring operation uneconomical. This is due to the fact that a small cross-section of the ingot mould necessitates a small cross-section for the immersion nozzle which projects into it. Having regard to the requirement of providing a sufficiently large flow cross-section for the molten stream of metal this results in the wall thickness of the nozzle being so small as to cause problems, particularly as regards wear resistance.

The wall thickness when using conventional material is in any event in practice limited to a lower limit of 10 mm due to the properties of the materials. The closer the wall thickness comes to this lower limit the shorter the service life of the immersion nozzle.

The manufacture of immersion nozzles with a small wall thickness is extremely difficult and a relatively high proportion of wastage and breakage occurs.

Having regard to these problems it is an object of the present invention to provide an immersion nozzle for use with ingot moulds having a small pouring cross-section, primarily for casting billets the length of whose sides is less than 125 mm, which has a relatively long service life and high resistance to breakage and is simple to manufacture with a relatively small wall thickness.

According to the present invention there is provided a refractory immersion nozzle, particularly for pouring molten steel into ingot moulds of small cross-section from continuous billet casting installations, in which at least that end of the nozzle which, in use, is immersed comprises a pouring tube of ceramic oxide material. The thickness of the wall of the pouring tube is preferably less than 10 mm and may be as low as 5 mm but the nozzle nevertheless has an excellent service life which can as much as triple the casting time whereby casting may be effected economically even when the ingot mould is extremely small. The pouring tube is preferably isostatically pressed or extruded and may be simply manufactured with a mechanical stability which is resistant even to rouch handling.

The pouring tube preferably comprises one or more oxides with a melting point above 1950"C and preferably comprises stabilised Zr02. Such materials have a high resistance to thermal shock.

The entire immersion nozzle may be constructed as a single unit of ceramic oxide material. Alternatively, the nozzle may be of two-part construction with a refractory support flange extending around the end of the pouring tube remote from the end which, in use, is immersed. The support flange may be of refractory concrete moulded around the pour ing tube or it may be prefabricated and cemented to the pouring tube. In both embodiments which are found to be particularly suitable for practical use an external metal shell is preferably provided which covers the whole or a part of the external surface of the nozzle and serves to reinforce and protect the nozzle when being handled. The sheet metal shell can be used as a lost mould for moulding a support flange of refractory concrete around the pouring tube.

In one embodiment of the invention the support flange is substantially gas impermeable and a porous ceramic ring or a space extends around the pouring tube within the support flange and is connected to a gas connection, whereby flushing or scavenging gas may be introduced into the pouring tube at any time in accordance with requirements.

One exemplary embodiment of the invention will be described below with reference to the single drawing which is a longitudinal sectional view of an immersion nozzle.

The nozzle comprises a circular section ceramic oxide pouring tube 1 whose upper end is received in a support flange 2 for connection to a pouring vessel which is not illustrated for the sake of simplicity. The free lower end of the nozzle is shown extending into a continuous casting ingot mould 3 which has a relatively small cross-section and serves to cast steel billets, the length of the sides of the cross-section of which is less than 125 mm. The pouring tube 1 and the support flange 2 are surrounded by a sheet metal shell 4 which reinforces and protects the immersion nozzle.

In a modified embodiment which is not illustrated a prefabricated pouring tube 1 is centrally set in a pre-fabricated sheet metal shell 4 and concrete is poured into the shell to form the support flange 2.

This is found to be a particularly simple method of manufacture.

If the pouring tube is cemented into a prefabricated support flange 2 the sheet metal shell 4 may be applied subsequently. The shell 4 may cover only part of the exterior of the pouring tube 1, for instance that portion of the pouring tube which extends out of the support flange 2 in which event the support flange 2 merely serves as a securing basis for the sheet metal shell 4.

A porous ceramic ring 5 extends around the pouring tube 1 within the support flange 2 and communicates with a gas connection 6 and may be used to introduce a flushing or scavenging gas into the pouring tube.

1. A refractory immersion nozzle in which at least that end of the nozzle which, in use, is immersed comprises a pouring tube of ceramic oxide material.

2. A nozzle as claimed in claim 1 in which the wall thickness of the pouring tube is less than 10 mm.

3. A nozzle as claimed in claim 1 or claim 2 in which the pouring tube comprises one or more

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Refractory immersion nozzles The invention relates to refractory immersion nozzles, particularly for pouring molten steel into ingot moulds of small cross-section from continuous billet casing installations. With ingot moulds having a small pouring crosssection, whose sides are less than 125 mm long, conventional immersion nozzles manufactured from conventional refractory materials, for instance, alumina-graphite or vitreous silica, have only a short service life and thus do not permit a continuous pouring operation thereby rendering the pouring operation uneconomical. This is due to the fact that a small cross-section of the ingot mould necessitates a small cross-section for the immersion nozzle which projects into it. Having regard to the requirement of providing a sufficiently large flow cross-section for the molten stream of metal this results in the wall thickness of the nozzle being so small as to cause problems, particularly as regards wear resistance. The wall thickness when using conventional material is in any event in practice limited to a lower limit of 10 mm due to the properties of the materials. The closer the wall thickness comes to this lower limit the shorter the service life of the immersion nozzle. The manufacture of immersion nozzles with a small wall thickness is extremely difficult and a relatively high proportion of wastage and breakage occurs. Having regard to these problems it is an object of the present invention to provide an immersion nozzle for use with ingot moulds having a small pouring cross-section, primarily for casting billets the length of whose sides is less than 125 mm, which has a relatively long service life and high resistance to breakage and is simple to manufacture with a relatively small wall thickness. According to the present invention there is provided a refractory immersion nozzle, particularly for pouring molten steel into ingot moulds of small cross-section from continuous billet casting installations, in which at least that end of the nozzle which, in use, is immersed comprises a pouring tube of ceramic oxide material. The thickness of the wall of the pouring tube is preferably less than 10 mm and may be as low as 5 mm but the nozzle nevertheless has an excellent service life which can as much as triple the casting time whereby casting may be effected economically even when the ingot mould is extremely small. The pouring tube is preferably isostatically pressed or extruded and may be simply manufactured with a mechanical stability which is resistant even to rouch handling. The pouring tube preferably comprises one or more oxides with a melting point above 1950"C and preferably comprises stabilised Zr02. Such materials have a high resistance to thermal shock. The entire immersion nozzle may be constructed as a single unit of ceramic oxide material. Alternatively, the nozzle may be of two-part construction with a refractory support flange extending around the end of the pouring tube remote from the end which, in use, is immersed. The support flange may be of refractory concrete moulded around the pour ing tube or it may be prefabricated and cemented to the pouring tube. In both embodiments which are found to be particularly suitable for practical use an external metal shell is preferably provided which covers the whole or a part of the external surface of the nozzle and serves to reinforce and protect the nozzle when being handled. The sheet metal shell can be used as a lost mould for moulding a support flange of refractory concrete around the pouring tube. In one embodiment of the invention the support flange is substantially gas impermeable and a porous ceramic ring or a space extends around the pouring tube within the support flange and is connected to a gas connection, whereby flushing or scavenging gas may be introduced into the pouring tube at any time in accordance with requirements. One exemplary embodiment of the invention will be described below with reference to the single drawing which is a longitudinal sectional view of an immersion nozzle. The nozzle comprises a circular section ceramic oxide pouring tube 1 whose upper end is received in a support flange 2 for connection to a pouring vessel which is not illustrated for the sake of simplicity. The free lower end of the nozzle is shown extending into a continuous casting ingot mould 3 which has a relatively small cross-section and serves to cast steel billets, the length of the sides of the cross-section of which is less than 125 mm. The pouring tube 1 and the support flange 2 are surrounded by a sheet metal shell 4 which reinforces and protects the immersion nozzle. In a modified embodiment which is not illustrated a prefabricated pouring tube 1 is centrally set in a pre-fabricated sheet metal shell 4 and concrete is poured into the shell to form the support flange 2. This is found to be a particularly simple method of manufacture. If the pouring tube is cemented into a prefabricated support flange 2 the sheet metal shell 4 may be applied subsequently. The shell 4 may cover only part of the exterior of the pouring tube 1, for instance that portion of the pouring tube which extends out of the support flange 2 in which event the support flange 2 merely serves as a securing basis for the sheet metal shell 4. A porous ceramic ring 5 extends around the pouring tube 1 within the support flange 2 and communicates with a gas connection 6 and may be used to introduce a flushing or scavenging gas into the pouring tube. CLAIMS

3. A nozzle as claimed in claim 1 or claim 2 in which the pouring tube comprises one or more oxides with a melting point about 1 950C.

4. A nozzle as claimed in any one of claims 1 to 3 including a support flange of refractory concrete moulded around the end off the pouring tube remote from the end which, in use, is immersed.

5. A nozzle as claimed in any one of claims 1 to 4 including a prefabricated refractory support flange cemented to the end of the pouring tube remote from the end which, in use, is immersed.

6. A nozzle as claimed in any one of the preceding claims including a metal shell extending over at least part of its external surface.

7. A nozzle as claimed in claim 3 or claim 4 in which the support flange is substantially gas impermeable and a porous ceramic ring or a space extends around the pouring tube within the support flange and is connected to a gas connection, whereby gas may be introduced into the pouring tube.

8. A refractory immersion nozzle substantially as specifically herein described with reference to the accompanying drawing.

9. A method of casting a billet in which molten metal is permitted to flow through an immersion nozzle as claimed in any one of the preceding claims into an ingot mould, the length of at least one of the sides of the cross-section of which is less than 125 mm.