GB1581058A

GB1581058A - Steel casting

Info

Publication number: GB1581058A
Application number: GB1284277A
Authority: GB
Original assignee: ROBSON REFRACTORIES
Current assignee: ROBSON REFRACTORIES
Priority date: 1978-03-23
Filing date: 1978-03-23
Publication date: 1980-12-10

Description

(54) IMPROVEMENTS IN AND RELATING TO STEEL CASTING (71) We, ROBSON REFRACTORLES LIMI TED, of Allingtotl Way, Yarm Road, Darlington, County Durham, a British corn pany, 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 a device for use in casting steel.

In the casting of steel, ladles are used to convey the steel to where it is to be discharged. This may typically be into an ingot mould or into the tundish of a continuous casting machine. The steel is discharged through an orifice in the ladle usually located in the bottom of the ladle.

Until recently the flow of steel through this orifice or nozzle has been controlled by means of a stopper rod assembly. Movement up or down of the stopper rod increased or decreased the flow of steel from the ladle. When the ladle is being filled with steel the stopper rod is closed tight against the nozzle.

Recently a different type of mechanism to control the flow of steel from the ladle has been developed. This mechanism obviated the need for a stopper assembly to pass through the molten steel by having a sliding gate valve located and actuated at the bottom of the ladle. An advantage of this type of control arrangement is that all the operating pieces of the valve are outside the ladle thus obviating problems which occur from time to time with stopper rod assemblies passing through liquid steel.

These problems which are mainly of a refractory nature, have tended to increase as ladle size has increased and hence the time the stopper rod assemblies have remained in contact with the molten steel have increased.

One difference between the traditional stopper rod method of controlling steel flow and the more recent bottom of the ladle valves, is that when a ladle is empty and about to be filled with steel, whereas with the stopper rod type the orifice or nozzle through which the steel flows out of the ladle is closed at the end inside the ladle by the stopper rod head, with the bottom valve type the steel out off and control point is at the bottom of the exit nozzle.

With a bottom valve ladle when steel is poured into it the steel rapidly fills the exit nozzle. In some cases due to the intense heat sink around the exit nozzle this steel solidifies so that when the valve is opened the steel in the ladle does not flow out.

Resort is then often made to using oxygen lances or other means to burn out the solidified steel in the nozzle to allow the ladle to be emptied. A similar blocking effect can be created with debris or skull falling side the exit or inner nozzle before the ladle is filled with steel.

To overcome this problem it has become a practice to fill the exit or inner nozzle with a loose refractory type filler prior to filling the ladle with steel. Examples of this are chromite sand, or chromite sand mixed with graphite. The object of doing this is to prevent steel and/or slag or other debris settling and helping to block up the exit nozzle or nozzles. When the exit valve is opened the filler is then supposed to flow out followed by the steel. In some cases after the valve has been opened it is necessary to use an oxygen lance to open a path for the steel through the nozzle. The block age often occurs at the end of the exit or inner nozzle in the ladle and may be due to a reaction between the steel and filler forming a material which effectively blocks the nozzle. Other causes may be skull or debris in the ladle forming a layer across the nozzle which has to be cut through or re-.

moved before steel flows out.

The filler material mentioned before is often placed in the inner nozzle by means of a funnel and tube from the top of the ladle whilst the ladle is in an upright position. As ladles have become larger this has become rather a laborious job and in some cases hazardous. It is also not always easy to check that the nozzle has been properly filled. The object of this invention is to alleviate the difficulties outlined above.

The invention provides an insert, com prising a tubular sheath filled with a particulate refractory material. The length of the insert is made such that it meets the operating requirements of each particular ladle nozzle. The total insert can be made of one or more lengths of tubing.

The material of the insert sheath can be that which is suitable to perform satisfactorily. Cardboard, plastic, aluminium and steel have been satisfactorily used in trials.

The insert should fit reasonably snugly into the nozzle. It is sometimes advantageous to have the inserts protruding past the ladle end of the insert nozzle into the ladle itself. This may help ensure that any skull or debris is kept away from the inner nozzle and any reaction between the filler and steel occurring is such that it does not stop a clean valve opening. By clean is meant an opening where the steel flows out when the valve is opened and which does not require the assistance of say an oxygen lance. Clean openings are important as the use of say an oxygen lance causes delay and its use can be hazardous.

The invention will be more particularly described with reference to the accompanying drawings, wherein Fig. 1 is a dia grammatic cross-section of the lower part of a casting ladle, with a first embodiment of insert, and Fig. 2 an enlarged fragmentary view showing use of a second embodiment of insert.

As shown in Fig. 1 the bottom of a ladle, generally shown as 10, has a refractory nozzle 15, for allowing egress of molten metal. Flow of metal from nozzle 15 is controlled by a valve comprising a lower fixed plate 11 with a bore 14 aligned with the bore 15, and a slidable plate 12 wherein an aperture 13, normally out of alignment with bores 14 and 15, is slidably aligned with them to allow pouring by moving the plate 12. Before charging metal into the ladles in accordance with the invention, there is located in the nozzle 15 an insert comprising a tubular member 16, of removable material, e.g. combustible or fusible and/or metal filled with a suitable refractory material or mixture 17. The enlarged view of Fig. 2 differs from Fig. 1 in that the insert comprises a tubular cartridge 16a which has an axial length greater than the nozzle 15 and well block 20, it is similarly charged with a suitable refractory material or predominantly refractory mixture 17, for instance chromite sand and graphite. The longer tube 16a is of assistance in keeping the well block 20 and the nozzle 15 clear of skull or debris.

The insert tube 16 or 16a may be of cardboard plastic material, aluminium or steel.

The insert tube 16 or 16a may have a push fit upper end cap 18 in the form of a lid and a bottom cap 19 either wholly or partly in the form of a foil membrance.

When the ladle is to be emptied of metal the slidable plate 12 is moved to bring the aperture 13 into line with bores 14 and 15.

When this is done the refractory filler in the tube 16 or 1 6a should fall out followed byrthe metal. Sometimes it is necessary to assist the egress of metal by prodding through the nozzle 15 often with an oxygen lance possibly to perforate or displace caps 18, 19 andlor remove any hard crust of material which has formed in the well block 20 preventing the egress of the metal from the ladle through the nozzle 15. The tube 16 or 16a may or may not be destroyed by contact with the hot metal, but will not normally be reusable.

The insert can be inserted from the bottom of the ladle through into the nozzle an easy and safe process.

The insert is preferably packed with a suitable refractory or similar filler, e.g.

chromite sand, or chromite sand mixed with graphite.

WHAT WE CLAIM IS:- 1. In a casting ladle of the type described an insert for insertion into a discharge nozzle thereof, said insert comprising a tubular sheath filled with a particulate refractory material.

2. An insert according to Claim 1, wherein the sheath is made from any one or 'more of cardboard, steel, plastics or aluminium.

3. An insert acording to Claim 1 or 2, wherein' the sheath is filled with chromite sand.

sand.

4. An insert according to Claim 1 or wherein the sheath is filled with a mixture of chromite sand and graphite.

5. An insert according to any proceeding claim wherein the sheath is of an axial length greater than that of the discharge nozzle and protrudes into the interior of the ladle.

6. An insert according to any preceding claim, wherein said sheath has end cans capable of being breached by an unignited lance.

7. An insert according to Claim 6, wherein the bottom end cap comprises a metal foil membrane.

8. An insert according to Claim 6 or 7, wherein the top end cap comprises a dis placeable push fit lid.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. prising a tubular sheath filled with a particulate refractory material. The length of the insert is made such that it meets the operating requirements of each particular ladle nozzle. The total insert can be made of one or more lengths of tubing. The material of the insert sheath can be that which is suitable to perform satisfactorily. Cardboard, plastic, aluminium and steel have been satisfactorily used in trials. The insert should fit reasonably snugly into the nozzle. It is sometimes advantageous to have the inserts protruding past the ladle end of the insert nozzle into the ladle itself. This may help ensure that any skull or debris is kept away from the inner nozzle and any reaction between the filler and steel occurring is such that it does not stop a clean valve opening. By clean is meant an opening where the steel flows out when the valve is opened and which does not require the assistance of say an oxygen lance. Clean openings are important as the use of say an oxygen lance causes delay and its use can be hazardous. The invention will be more particularly described with reference to the accompanying drawings, wherein Fig. 1 is a dia grammatic cross-section of the lower part of a casting ladle, with a first embodiment of insert, and Fig. 2 an enlarged fragmentary view showing use of a second embodiment of insert. As shown in Fig. 1 the bottom of a ladle, generally shown as 10, has a refractory nozzle 15, for allowing egress of molten metal. Flow of metal from nozzle 15 is controlled by a valve comprising a lower fixed plate 11 with a bore 14 aligned with the bore 15, and a slidable plate 12 wherein an aperture 13, normally out of alignment with bores 14 and 15, is slidably aligned with them to allow pouring by moving the plate 12. Before charging metal into the ladles in accordance with the invention, there is located in the nozzle 15 an insert comprising a tubular member 16, of removable material, e.g. combustible or fusible and/or metal filled with a suitable refractory material or mixture 17. The enlarged view of Fig. 2 differs from Fig. 1 in that the insert comprises a tubular cartridge 16a which has an axial length greater than the nozzle 15 and well block 20, it is similarly charged with a suitable refractory material or predominantly refractory mixture 17, for instance chromite sand and graphite. The longer tube 16a is of assistance in keeping the well block 20 and the nozzle 15 clear of skull or debris. The insert tube 16 or 16a may be of cardboard plastic material, aluminium or steel. The insert tube 16 or 16a may have a push fit upper end cap 18 in the form of a lid and a bottom cap 19 either wholly or partly in the form of a foil membrance. When the ladle is to be emptied of metal the slidable plate 12 is moved to bring the aperture 13 into line with bores 14 and 15. When this is done the refractory filler in the tube 16 or 1 6a should fall out followed byrthe metal. Sometimes it is necessary to assist the egress of metal by prodding through the nozzle 15 often with an oxygen lance possibly to perforate or displace caps 18, 19 andlor remove any hard crust of material which has formed in the well block 20 preventing the egress of the metal from the ladle through the nozzle 15. The tube 16 or 16a may or may not be destroyed by contact with the hot metal, but will not normally be reusable. The insert can be inserted from the bottom of the ladle through into the nozzle an easy and safe process. The insert is preferably packed with a suitable refractory or similar filler, e.g. chromite sand, or chromite sand mixed with graphite. WHAT WE CLAIM IS:-

1. In a casting ladle of the type described an insert for insertion into a discharge nozzle thereof, said insert comprising a tubular sheath filled with a particulate refractory material.

sand.

9. An insert for insertion into a dis

charge nozzle of a casting ladle, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.