GB2135918A - Pouring tube for casting steel - Google Patents

Abstract

A composite delivery outlet (1) for casting plant has an inner lining (2) made of magnesium oxide, to prevent the accumulation of solid oxide deposits. An outer layer (3) of a refractory oxide such as Al2O3 or SiO2 is provided to strengthen the outlet, the two layers being spaced by an air gap (4). <IMAGE>

Description

SPECIFICATION Delivery outlet for continuous casting plant The invention concerns a delivery outlet for continuous casting plant made of a refractory material which prevents the accumulation of solid oxide deposits.

In the continuous casting of steel delivery outlets are used which consist essentially of one or more fire-resistant oxides (Al203, SiO2), carbon (graphite) and a binding agent. In these outlets alumina deposits form on the inner walls and cause a diminution of the internal diameter of the outlet, which results in a reduction in the speed of flow.

Moreover, pieces of alumina broken off from these deposits form inclusions which impair the finished steel.

A known method of prevention (DE-OS 27 31 367) is to add Ca or CaSi alloys to the molten steel in order to prevent the deposition of alumina particles in the delivery outlet. In this way the Awl203 particles resulting from an aluminium treatment are modified, i.e. they are converted to a liquid form (Ca aluminates).

This procedure is not always successful. It is also laborious and costly. Finally it does not take account of the fact that in delivery outlets of Awl203 or SiO3 deposits or accumulations form on the internal wall as a result of reactions between the refractory mass of the outlet, alumina or silicon dioxide as the molten steel.

The invention has a purpose of proposing a delivery outlet for continuous casting plant in which accumulations of solid oxide phases are prevented.

According to the invention this is achieved by making the inner part of the outlet which comes into contact with the molten steel of magnesium oxide.

It is expedient to surround the inner part of the outlet with a layer of refractory oxides commonly used in outlets, such as At203 or SiO2.

In accordance with a further development of the invention an air gap is provided between the inner part and the layer surrounding it.

The essential advantage to be obtained by the invention is that by a simple expedient the disruptive deposits on the inner walls of delivery outlets are prevented and thus the disadvantages mentioned earlier are not suffered.

The drawing shows an example of the application of the invention.

The inner part (2) of the delivery outlet (1), the part which comes into contact with the molten steel, is made of magnesium oxide (MgO). It has proved expedient to surround the inner part (2) with a layer (3) of known refractory oxides such as for example Al203, SiO2 or another suitable fire-resistant material. In this way the delivery outlet (1) is sufficiently durable in spite of the not very good mechanical strength of MgO.

If the coefficients of expansion of the inner part (2) and the outer layer (3) are very different it is appropiate to provide an air gap (4).

Tests have shown that surprisingly the delivery outlet described remains clean in its inner part (2), so that casting can continue at a constant speed.

1. A composite delivery outlet for continuous casting plant, made of a refractory material, wherein the inner part of the outlet, which comes into contact with the molten steel, is made of magnesium oxide to prevent the accumulation of solid oxide deposits.

2. A composite delivery outlet in accordance with Claim 1, wherein the said inner part of the outlet is surrounded by a layer of a refractory oxide or oxides.

3. A composite delivery outlet in accordance with Claim 2 wherein the surrounding refractory oxide layer comprises A1203 and/or SiO2.

4. A composite delivery outlet in accordance with Claim 2 or Claim 3, wherein an air gap is provided between the inner part and the surrounding refractory oxide layer.

5. A composite delivery outlet for continuous casting plant, substantially as herein described with reference to the acompanying drawing.

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

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Delivery outlet for continuous casting plant The invention concerns a delivery outlet for continuous casting plant made of a refractory material which prevents the accumulation of solid oxide deposits. In the continuous casting of steel delivery outlets are used which consist essentially of one or more fire-resistant oxides (Al203, SiO2), carbon (graphite) and a binding agent. In these outlets alumina deposits form on the inner walls and cause a diminution of the internal diameter of the outlet, which results in a reduction in the speed of flow. Moreover, pieces of alumina broken off from these deposits form inclusions which impair the finished steel. A known method of prevention (DE-OS 27 31 367) is to add Ca or CaSi alloys to the molten steel in order to prevent the deposition of alumina particles in the delivery outlet. In this way the Awl203 particles resulting from an aluminium treatment are modified, i.e. they are converted to a liquid form (Ca aluminates). This procedure is not always successful. It is also laborious and costly. Finally it does not take account of the fact that in delivery outlets of Awl203 or SiO3 deposits or accumulations form on the internal wall as a result of reactions between the refractory mass of the outlet, alumina or silicon dioxide as the molten steel. The invention has a purpose of proposing a delivery outlet for continuous casting plant in which accumulations of solid oxide phases are prevented. According to the invention this is achieved by making the inner part of the outlet which comes into contact with the molten steel of magnesium oxide. It is expedient to surround the inner part of the outlet with a layer of refractory oxides commonly used in outlets, such as At203 or SiO2. In accordance with a further development of the invention an air gap is provided between the inner part and the layer surrounding it. The essential advantage to be obtained by the invention is that by a simple expedient the disruptive deposits on the inner walls of delivery outlets are prevented and thus the disadvantages mentioned earlier are not suffered. The drawing shows an example of the application of the invention. The inner part (2) of the delivery outlet (1), the part which comes into contact with the molten steel, is made of magnesium oxide (MgO). It has proved expedient to surround the inner part (2) with a layer (3) of known refractory oxides such as for example Al203, SiO2 or another suitable fire-resistant material. In this way the delivery outlet (1) is sufficiently durable in spite of the not very good mechanical strength of MgO. If the coefficients of expansion of the inner part (2) and the outer layer (3) are very different it is appropiate to provide an air gap (4). Tests have shown that surprisingly the delivery outlet described remains clean in its inner part (2), so that casting can continue at a constant speed. CLAIMS

1. A composite delivery outlet for continuous casting plant, made of a refractory material, wherein the inner part of the outlet, which comes into contact with the molten steel, is made of magnesium oxide to prevent the accumulation of solid oxide deposits.

2. A composite delivery outlet in accordance with Claim 1, wherein the said inner part of the outlet is surrounded by a layer of a refractory oxide or oxides.

3. A composite delivery outlet in accordance with Claim 2 wherein the surrounding refractory oxide layer comprises A1203 and/or SiO2.

4. A composite delivery outlet in accordance with Claim 2 or Claim 3, wherein an air gap is provided between the inner part and the surrounding refractory oxide layer.

5. A composite delivery outlet for continuous casting plant, substantially as herein described with reference to the acompanying drawing.