Regardless of whether the crude steel is produced from ore-based or scrap-based raw material, it is transferred to a ladle metallurgy station in which the operators carry out fine adjustment of the temperature, composition and quantities of various alloying elements. The limits of composition are very close and the tolerances are tight. Every steel grade has a unique recipe that must be followed accurately. The operators use computers and analysis samples, with fast laboratory responses for checking that the steel contains the right quantities of the correct ingredients and is at the right temperature.
The ladle treatment methods vary between the four SSAB steelworks, since they use three different process methods. But the purpose, requirements and accuracy are the same.
The steel may also undergo vacuum treatment to achieve extremely high purity, e.g., for hydrogen and nitrogen removal. The composition is dependent on the field of application.
Steel with precision
The SSAB recipe books contain almost 500 different steel grades. The accuracy is determined in parts per thousand and sometimes right down to parts per million. Whether the steel is to be hard or soft is determined in the ladle metallurgy process. The recipe follows every ladle right back from the first steelworks treatment stage at the desulphurizing station up to the LD converters and the ladle metallurgy process.
The SSAB method of using different carbon contents, alloying with other metals and small doses of other additives produces the chemistry of the steel that yields its internal strength and formability. SSAB high strength steels belong to the family of low-alloy steel grades. Using small amounts of additives and high accuracy, operators in the SSAB ladle metallurgy process create the composition for many different end grades.
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