Basic oxygen process
Basic Oxygen Process
The oldest process for making steel in large quantities, the Bessemer process, made use of a tall, pear-shaped furnace, called a Bessemer converter that could be tilted sideways for charging and pouring. Great quantities of air were blown through the molten metal; its oxygen united chemically with the impurities and carried them off.
In the basic oxygen process, steel is also refined in a pear-shaped furnace that tilts sideways for charging and pouring. Air, however, has been replaced by a high-pressure stream of nearly pure oxygen. After the furnace has been charged and turned upright, an oxygen lance is lowered into it. The water-cooled tip of the lance is usually about 2 m above the charge although this distance can be varied according to requirements. Thousands of cubic meters of oxygen are blown into the furnace at supersonic speed. The oxygen combines with carbon and other unwanted elements and starts a high-temperature churning reaction that rapidly burns out impurities from the pig iron and converts it into steel. The refining process takes 50 min or less; approximately 275 metric tons of steel can be made in an hour.