How Carbon Steel is Made
The new ThyssenKrupp state-of-the-art processing facility will employ the most modern technology available today.
It is important to note that, unlike traditional production mills, this new facility will not “produce” carbon steel. Instead it will “process” carbon steel as pre-cast slabs will be shipped to the plant for processing.
Because it is not a carbon steel manufacturing facility, this mill will not use conventional coke ovens or blast furnaces in its operations to produce hot metal.
The ThyssenKrupp facility will utilize clean-burning natural gas to fire its process heaters, furnaces and other combustion sources. The process equipment has been designed with extensive energy recovery and re-use technologies.
The final carbon steel product will be cut into coil, plate and strip for use by end users in many industries, including automotive, appliance, construction and packaging.
Following is an overall summary of how carbon steel is produced.
The Steel Making Process
The steel making process starts at the blast furnace. Iron ore, coke and additional feedstock are placed into the blast furnace. The coke serves as an agent to reduce the iron ore and to generate the necessary heat. The iron ore is converted into molten hot metal. The liquid hot metal and slag are tapped off at the lower end of the blast furnace.
The hot metal is further processed in the melting shop. Mixed with recycled steel scrap and other alloys in a basic oxygen furnace, the hot metal is converted into steel.
70% iron and 30% recycled steel are mixed with other alloys in the 300-ton basic oxygen steel-making furnace to create the exact metallurgical qualities.
The molten steel is poured into the casting machine to make steel slabs.
All of the cast slabs produced are reheated to about 1200 degrees Centigrade in reheating furnaces to ensure uniform temperatures prior to rolling into strip.
The 30-foot long slabs are reduced to sizes from 8.5 inches to less than two inches after five passes in the “roughing mill” as an intermediate step before rolling to exact thickness in the finishing mill.
The two inch thick steel strip now extends about 120 feet in length and is sent to the finishing mill where it is further reduced to a range of thickness from .059 inches to .5 inches.
The strip of hot rolled steel is wound into a coil. This steel is sold to customers for processing into steel products for automobiles, pipes, tubing and construction.
Hot rolled steel can also be earmarked for further processing or coating for use in various other applications. The first step is to ‘pickle’ the steel before further processing by removing surface scale before it is cold rolled.
Cold Rolling reduces the steel to exact thickness and flatness requirements. This product can be sold for use in a wide range of applications in the construction, automotive, appliance and manufacturing industries.
The cold rolled steel can also be tempered to give it greater hardness, or annealed to provide formability before it is sold. A zinc coating is added at a galvanizing line. Galvanized steel is used in products where its corrosion resistant qualities are desirable. The cold rolled steel can also be plated with tin for use in packaging.
Steel is 100% recyclable and can be recycled infinitely without ever affecting its strength or durability.