Metalwork - Materials - Basic Oxygen Furnace
The vast majority of Steel manufactured in the world is produced using the Basic Oxygen Furnace. Below you can see a diagram of the Furnace with its main parts labeled. If you click on the parts you will be taken to an explanation of them. If you want to find out how the Furnace works click on the link below.
Diagram of the Basic Oxygen Furnace
The Water-Cooled Oxygen Lance provides the oxygen to the Furnace so that the temperature in the Furnace will increase. The Oxygen that comes through the Lance is extremely hot after coming through special heating ovens. The Lance has to be Water-Cooled so that it will not melt in the Furnace.
The Slagging Hole is like a spout where the slag can be poured out when necessary. During the manufacture of the Steel the Slagging Hole is "plugged" so that no heat can escape.
The main body of the Basic Oxygen Furnace is made from Steel, as the material is strong and durable, or tough. The Steel Shell does not melt because of the Refractory Lining.
The Refractory Lining is a special type of cement that has the ability to refelct heat. You are more familiar with what a Refractory Lining is than you might think. If you look at the back of an open fireplace, the cement you see on the back wall is a Refractory material, although it would not be of the same quality as the Refractory lining in a Furnace. The Refractory Lining has two purposes. The first is to keep the heat from the furnace in so that less energy is required to keep the Furnace at operating temperature. The second reason is to protect the Steel Shell of the Furnace.
The Molten Metal at the bottom of the Furnace is the Steel. The Steel is below the Slag as it is heavier or denser. The Molten Steel is removed from the Furnace when the Steel is of the correct consistency, through the Tapping Hole.
The Slag which sits on top of the Molten Metal, because it is less dense, is the waste material from the process of creating Steel. It consists of the impurities, that is most materials other than Iron and Carbon which were put into the Furnace at the start when the Furnace was being Charged. The Slag is removed from the Furnace when the time is ready through the Slagging Hole.
The Tapping Hole is used to remove the Molten Steel from the Furnace when it is of the right consistency. During the process of manufacturing the Tapping Hole is "plugged" so as not to allow heat to escape from the Furnace.
The Gas Offtake Hood has two purposes. The first is to trap the dangerous gases that the Basic Oxygen Process produces so that they cannot escape into the atmosphere to poison people or create Acid Rain. The gases are "cleaned" or put to other uses. One important use of the gases is to heat the Oxygen that is going through the Water-Cooled Oxygen Lance. The second purpose of the Gas Offtake Hood is to reduce the amount of heat loss in the Furnace.
There are six steps in the production of Steel using the Basic Oxygen Process. During each stage of the process the Furnace is turned in different directions. This is shown clearly in the accompanying diagrams. Below are the stages of the process.
Scrap Iron and Steel are tipped into the Furnace. The Iron and Steel comes from old or scraped cars, bridges, buildings, etc. Also used is Iron or Steel that when manufactured into a product was not of good enough quality to be used for its intended purpose.
Molten Iron, which comes straight from the Blast Furnace is then tipped into the Furnace. The Furnace is now ready for the blow.
The Gas Offtake Hood is lowered onto the Furnace. The water cooled Oxygen Lance is then lowered. This carries the hot Oxygen to the surface of the hot metal, increasing the temperature in the Furnace and melting all of the metal. The Oxygen combines with the impurities to form oxides in the form of gases and slag.
During the Blow the temperature of the Furnace is monitored, and at regular intervals samples of the molten metal are taken to be analysed. When the Steel is of the right composition, then the Steel workers can move onto the next stage.
When the Steel is of the right composition the Gas Offtake Hood and the Oxygen Lance are removed. The molten Steel is then poured out the Taphole by turning the Furnace to one side. The Steel is then cast into ingots, or processed by continuous casting.