Steel Manufacturing (Including Blast Furnace and BOS)

What is Steel?

This section explains what steel is and how it is used.

Steel Composition

• Steel is used to make a wide range of products, including cars, buildings, bridges, ships, knives and forks, fridges and washing machines, food and drink cans, train tracks.

• Steel is made from iron ore, coke and limestone. Molten iron is produced by heating these materials in a blast furnace. The molten iron then needs to be refined to remove impurities such as carbon and silicon before other elements are added to adjust the steel's composition.

• Steel is an alloy of mainly iron and carbon with a carbon content between 0.02% and 1.5%.

Production Process

• Iron ore is mined in places such as the Americas, Australia and Scandinavia before being shipped around the world to steelworks where it's blended together with coke to produce sinter.

• Carbon in the form of coke is required for the blast furnace. Coking coal is heated in an oven which drives off volatile byproducts leaving carbon gas that can be used as fuel while other byproducts such as tar and sulfur are extracted.

• Raw materials sinter iron ore and coke meet each other at the blast furnace where they are fed into the top of the furnace along with some limestone. A hot air blast from which the furnace gets its name raises temperature in the furnace to white-hot intensity around 2,200 degrees centigrade needed for chemical reduction & melting of sinter & iron ore forming molten iron.

• The molten iron we get from a blast furnace or hot metal as it's known in the industry isn't pure iron and contains elements such as carbon, sulfur, phosphorus, manganese and silicon. To make steel these elements must be removed or reduced and other elements added depending on the type of steel being made.

• Basic oxygen steelmaking (BOS) is the main bulk production process for refining iron into steel. BOS vessels can take up to 350 tons of molten iron at a time and convert it into steel in less than 30 minutes. First scrap steel is put into the vessel and then the hot metal is added which may have been pre-treated to remove elements such as sulfur. A lance then blows high purity oxygen onto the hot metal at about twice the speed of sound.

Electric Arc Furnace

• The other main method of making steel is by means of an electric arc furnace (EAF). The EAF process predominantly uses cold steel scrap making it one of the world's largest recycling processes. EAFs make up to 150 tons of steel in a single melt in less than an hour.

Steel Production Overview

This section provides an overview of the steel production process, including the different types of furnaces used and how steel is refined and shaped.

Furnaces Used in Steel Production

• Impurities in the metal combine to form a slag during the melting process.

• Electric arc furnaces (EAFs) are used for producing a variety of special steels, including alloy steels and stainless steels.

• Mini mills are small steel-producing plants that operate with EAFs closely linked to casting and rolling facilities. These can produce relatively low volumes of specialist products.

Refining Steel

• Secondary steelmaking processes are used to further refine the steel after BOS or AAF steelmaking processes. These specialist processes improve consistency of temperature and composition within the steel, remove gases such as hydrogen, reduce elements like sulfur, and add alloys and slags.

• All these steps ensure that the final product meets exact customer specifications before casting.

Shaping Steel

• Continuous casting is used to solidify molten steel ready for shaping. The molten steel is poured through a gas-tight refractory tube into a tundish which feeds it through further gas-tight refractory tubes into water-cooled copper molds. The flow rate is controlled so that only the outer shell solidifies before being drawn from the bottom of the mold through support rolls and water sprays.

• Sections, rails, rods, wire and bar tubes, plates profiles, and strips are finished products that are the raw materials for thousands of other industries.

• Steel is generally rolled while hot to make sure it is at the correct temperature for rolling. The principles of hot rolling are the same, and steel is squeezed between rolls until the final thickness and shape are achieved.

• Mill stands have various roll arrangements depending on what product is being rolled. The simplest arrangement is a two-high stand, mainly used for long products such as sections, piling rails, and rod rolling. For light sections and bars, three-high stands are sometimes used with the steel passing one way through the back through the top gap. High stands have two work rolls in contact with the steel supported by larger back-up rolls to prevent distortion caused by the rolling face.

• Rolling processes are computer-controlled, monitored up to 50 times per second, and measured to an accuracy of plus or minus 50 microns.

Further Processing

• Rolled steel is cooled in a way appropriate to its end use and prepared for further processing or dispatch.

• Cold rolling of strength produces a thinner flatter product than it's possible on a hot mill down to a thickness of naught point one five millimeters forming properties and surface finish of cold rolled strip is better it can also be coated with zinc to protect it from corrosion with tin four cans and with a plastic coating or paint for protection and decorative purposes.

• There are two types of steel tube welded and seamless. For welded tube, flat steel strip or plate is formed into a cylinder either by rolling or pressing before welding edges together. To make seamless tubes, you must first pour a hole through a hot billet either in a large press or by rolling the billet through special piercing rolls. The hollow billet is then stretched over a bar which enables the interior of the tube to be sized.

Steel Manufacturing Processes

This section discusses the processes used to manufacture steel, the world's most versatile material. It highlights the importance of efficient and safe operations, skilled operators, complex logistics support, and computer control in producing quality steels.

Steel Production Processes

• The production of quality steels requires sophisticated computer control and skilled operators.

• There are thousands of different types of steel, each with different properties suitable for various uses.

• New steels are continuously researched and developed to offer better properties to meet ever-greater demands.

• Almost 400 million tons of steel are produced every year worldwide.

Logistics Support

• Complex logistics support is essential for steel manufacturing and distribution of finished products to customers around the world.

Overall, this section provides an overview of the importance of efficient and safe operations in producing quality steels. It also highlights the significance of complex logistics support in steel manufacturing and distribution.