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Process Overview

Evraz Highveld’s iron and steel works annually produces around one million tons of steel blocks. Of this 40% is used to manufacture structural sections, engineering rounds and rails and 45% to manufacture plates and coiled plates and sheets. Some 15% of the steel produced is used to cast billets to be sold for re-rolling. Depending on market demand, billets may also be rolled.

Other products of the iron and steel works are titaniferous slag and high grade vanadium slag. The former is used effectively in blast furnace operations to prolong furnace life. The steel plant produces vanadium slag which is used to produce an alloy for high-strength steels.

The steel works consists of an iron making division, a steel plant equipped with four shaking ladles for vanadium extraction, three basic oxygen furnaces and four continuous casting machines; a universal structural mill, a plate mill and a hot strip mill.

Iron making consists of 13 pre-reduction kilns and seven electric sub-merged arc smelting furnaces.

Owing to the high titanium content of the magnetite ore Evraz Highveld receives from its Mapochs Mine, it cannot be smelted in the same way as more common iron ores in a conventional blast furnace, which relies on the presence of a large excess of carbon to reduce iron oxide to metallic iron.

Should this process be used to smelt magnetite ore, the carbon reduces the titanium dioxide content to titanium sequioxide, which then combines with the air blast to form titanium nitrides and carbides. This results in the precipitation into a solid agglomeration which shuts down the furnace by choking up the blast passages.

Evraz Highveld’s own innovative method of smelting the magnetite ore involves a preliminary "pre-reduction" stage. The ore is mixed with coal and fluxes, fed to rotary kilns and heated. This effects a degree of oxygen removal from the iron ore and complete charring of the coal; the danger of a titanium reaction is then eliminated. The pre-reduction stage, because it makes use of coal and not coke and has the effect of lowering the power requirements of the smelting, results in a cheaper iron-making process.

The hot pre-reduced charge from the pre-reduction kilns is smelted in submerged arc furnaces. The titanium separates from the molten pig iron and forms a dense slag which can be drawn off at the start of tapping. The molten pig iron contains about 3% carbon and about 1.25% vanadium. In Evraz Highveld’s steel plant the hot metal is agitated and oxygen-blown in shaking ladles to remove the vanadium. The process steps which follow are steelmaking, continuous casting and rolling.