The present invention relates to steel making, and materials for use in a steel making process.

In certain steel making processes (particularly processes producing"killed"steel, such as continuous casting processes) it is often required to reheat the molten steel before it can be sent to the continuous caster.

The conventional method for reheating steel is to add aluminium to certain process stages, and to subsequently inject oxygen by a lance. The oxidation of the aluminium is exothermic and the heat generated is transferred to the surrounding steel, thereby causing the desired reheat. At the end of the reheat, the steel may contain too much oxygen and further aluminium is required to'deoxidise the molten steel prior to completion. This method is expensive and can have detrimental effect upon the refractory lining of the ladle and certain elements of the treatment station.

In order to overcome this problem it is known to add a combination of separate batches of aluminium material and iron oxide, such as, millscale (the latter being a known by- product of steel making). The aluminium and the iron oxide react to provide aluminium oxide and iron; the heat

generated provides the required"reheat"for the molten steel. The separate addition of aluminium and iron oxide to the molten steel has the disadvantage that the resultant reaction between the aluminium and oxygen is not easily controlled.

Japanese patent application JP 030199305A discloses a method of raising the temperature of molten steel using a temperature raising agent. The temperature agent- disclosed, which comprises 15-25 weight % aluminium and 65- 85 weight % iron oxide, is subsequently added to molten steel. The iron oxide and the aluminium react in the molten steel exothermically thereby raising the temperature of the molten steel. The ratio of aluminium to iron oxide disclosed is within the stoichiometric ratio, therefore substantially all of the oxygen required to oxidise the aluminium is provided by the iron oxide. The use of such a temperature raising agent would be extremely volatile.

Such a material is disadvantageous as it is potentially dangerous. There is also the problem that arises during storage as care needs to be taken to ensure such an agent is not accidentally subjected to an elevated temperature, which would cause ignition.

It is therefore an aim of the present invention to provide a method of reheating steel which can alleviate at least some of the disadvantages highlighted above.

It is a further aim of the present invention to provide a method of reheating steel which requires reduced volume of

oxygen gas to be added to molten steel compared to prior art techniques.

It is yet a further aim of the present invention to provide an additive for use in the reheat of steel during the steel making process.

Therefore, according to a first aspect of the present invention, there is provided a shaped body comprising compressed material, which compressed material includes aluminium and ferrous material containing iron oxide (such as mill scale, iron ore and/or iron oxide) present in a ratio of 30-99%: 1 to 70% by weight, the shaped body being for use as an additive to molten steel and/or to iron in steel making typically in the reheating stage. The ferrous material preferably consists essentially of iron, oxygen and incidental ingredients and impurities.

It is envisaged that the actual ratio of aluminium to ferrous material is varied depending on the specific requirements of the plant (for example, the required speed of the oxidation of the aluminium). A particularly preferred ratio of aluminium to ferrous material is 40-95% : 5 to 60% by weight. If the ratio of aluminium to ferrous material is greater than this it becomes difficult to form a shaped body according to the invention, without the additional need for a binder. For example, the shaped body may include aluminium and ferrous material in any of the ratios identified below:

Aluminium Ferrous Material 90 10 80 20 70 30 60 40 50 50 40 60 Advantageously, when a temperature during steel making is at"liquid steel temperature", the aluminium and the ferrous material will react. The aluminium oxidises in an exothermic reaction with oxygen released from the iron oxide. The iron is released, in use, to the molten steel in the ladle. This has a further advantage of increasing the iron yield in the reaction.

According to a further aspect of the present invention, there is provided use of a shaped body which consists essentially of aluminium and ferrous material containing iron oxide, the ratio of aluminium to ferrous material being in the range 30 to 99%: 1 to 70% by weight, as an additive to molten steel (typically for use at a reheating stage).

According to yet a further aspect of the present invention, there is provided a shaped body for use as an additive to molten steel, the shaped body consisting essentially of aluminium and a ferrous material containing iron oxide, present in a ratio 30-99% aluminium to 1-70% ferrous metal by weight, substantially as described above. A degradable

binder (such as, for example, a wax based binder, hydrated lime, molasses or the like) may be present in some embodiments.

According to yet a further aspect of the present invention, there is provided a method of manufacturing a shaped body suitable for use as an additive to molten steel and/or iron in steel making which includes combining (typically under pressure) aluminium and ferrous material being present in a ratio 30 to 99% aluminium to 1 to 70% by weight ferrous material containing iron oxide, to create a shaped body.

The ferrous material may include mill scale preferably in cut or finely divided form, and may be classified or graded to a desired size before combining with the aluminium.

According to yet a further aspect of the present invention, there is provided a method of reheating steel which comprises adding a shaped body according to the first aspect of the present invention to molten steel and permitting exothermic oxidation of the aluminium so as to reheat the steel. Preferably the resulting reheated steel is subsequently cast in conventional manner to produce corresponding steel artefacts or bodies, which can then be shaped, formed or worked in a conventional way. For example, the steel may be used in continuous casting or the like.

It is envisaged that oxygen gas may also be bubbled through the molten steel, prior to, during or after, the addition of the shaped body. Therefore, there is a further

advantage of the present invention as the addition of oxygen assists the mixing of the molten steel.

Advantageously, a preferred ratio of aluminium to ferrous material is in the range 30 to 99% aluminium: 1 to 70% ferrous material by weight. Providing the aluminium and the ferrous material in such a ratio is particularly advantageous, as the ratio is not substantially close to the stoichiometric ratio. Providing a ratio close to the stoichiometric ratio is disadvantageous as the resultant reaction between the aluminium and the oxygen is vigorous and therefore more difficult to control. A stoichiometric ratio (or substantially close thereto), would provide the aluminium with substantially all of the oxygen (in the form of the oxide) required to oxidise the aluminium.

Higher proportions of aluminium may sometimes be desirable for maintaining the structural integrity of the mix.

It is envisaged that the reaction of the shaped body with the steel can be influenced by precise details of formulation, manufacturing method and/or dosing; a combination of these options may be required to give a controlled and gradual temperature rise in the molten steel. In addition the volume of oxygen lanced into the molten steel, is also controlled so as to control the reheat of the molten steel.

Use of the shaped body according to the present invention has the advantage that it permits lowering of the cost associated with reheating molten steel. In addition, there may be less trimming after treatment, which results in greater plant availability. There may also be less alumina pickup, in the steel which aids refractory life and steel quality. A major advantage of the present invention is that it can be used through existing treatment systems and requires no substantial modification of existing plant equipment.

The aluminium is preferably in the form of substantially pure aluminium, preferably greater than 80% pure aluminium.

The latter is, however, preferably recycled aluminium (. such as surplus or unusable material from aluminium production or forming processes).

The shaped body may also include a refractory filler and/or slag enhancing additive. Advantageously, the refractory filler assists in the control of the reaction between the aluminium and the iron oxide. These may include magnesia, fluorspar, limestone, lime and/or alumina. However, it should be apparent that this list is non-exhaustive. The slag enhancing additive is an additive to the shaped body which assists in the removal of alumina (and other undesirable compounds) present in the molten steel.

Preferred slag enhancing additives include lime and limestone. However, it should be apparent that this list is non-exhaustive.

The amount of refractory filler and/or the slag enhancing additive present in the shaped body depend on the specific requirements of the plant. However, it is preferred that the refractory filler and/or the slag enhancing additive are present in at least an amount which is either capable of controlling the chemistry, or slowing down (or indeed increasing) the rate of the reaction, according to the specific circumstances of the plant.