The final stage in the production of steel is, appropriately, steel making.

Steel Making Process Description
Iron from the blast furnace emerges free from many chemical impurities but infused with a small percentage of carbon, which produces a poor grade of steel. In the basic oxygen furnace (BOF), the iron is combined with varying amounts of steel scrap (less than 30 percent) and small amounts of flux, an additive similar to lime. After the materials are loaded into the furnace, they are exposed to a jet of pure oxygen, which combines with the carbon in the mixture and leaves the furnace as carbon monoxide and carbon dioxide. The purified molten iron, called carbon steel, remains in the furnace. A batch of iron is transformed into carbon steel in less than an hour in a BOF. Furnace air emissions (dust and gases) are removed from the air using air pollution control devices which produce "scrubber" wastewater.

After the steel making reaction is complete, the hot carbon steel is transferred to a giant ladle where other metals, such as nickel and chromium, can be added to produce steel alloys. An alloy is created when two or more metals are mixed to make a metal with properties different from the original metals. More than 1,000 steel alloys are produced every year. Most types of alloys undergo degassing to remove any gases that are dissolved in the liquid metal by exposure to an inert gas, such as argon, or a vacuum (vacuum degassing produces wastewater). When the desired metallic properties are achieved, the steel or the steel alloy is ready to be cast.

Steel Making Pollution Prevention Options
In contrast to iron making, many pollution prevention opportunities are available in steel making. Since the amount of scrap in the basic oxygen furnace (BOF) is limited by the ability to melt the scrap, if fuel is added with the oxygen, more scrap can be used. The use of more scrap in a BOF lowers the demand for iron and thus reduces the pollution associated with coke making and iron making. Despite increased energy consumption at the BOF, a net energy savings for the entire process can be achieved because the blast furnace operations required for iron production consume much more energy. With added fuel, it is possible that a scrap content of up to 50 percent could be achieved for BOF operations.

For BOFs, air emissions are proportional to the amount of time the metal spends at high temperatures. Typically, a tiny sample of hot metal must be removed for analysis of its chemical composition during the heating process. This step takes time, during which the heated steel is, in effect, "on hold." New analytical techniques such as laser plasma spectrophotometry can reduce the time required to determine when the steel is ready to be cast. These methods can decrease total BOF cycle time by 10 percent, or approximately two minutes, which would reduce the amount of dust particles generated. Similar options are available for mini mills.

The incorporation of more zinc into steel products is another potential pollution prevention strategy. Zinc contained in iron ore either goes into products or is removed as waste. Redesign of customer products or of purchasing specifications may allow for increased zinc content, which would result in decreased dust particle toxicity. A similar option is available for mini mills.

BOF dust particle recycling is not a pollution prevention strategy, but can make a difference in the generation of pollution. Some mills have experimented with dust recycling that allows the level of zinc to build up until it is high enough for recovery operations to be economically feasible.

Of the 550,000 pounds of dust generated every year, much is rich in zinc, chromium, and nickel. The recovery of these metals at a facility off-site is common. Currently, 50 percent of the demand for zinc in the United States is met with imports, which makes putting high zinc content dust in landfills not only pollution, but a waste of money.