World’s First Giga Steel
POSCO Gwangyang Steelworks has completed an automotive steel sheet production facility dedicated to giga steel for the first time in the world. The steelworks achieved such outcome in 30 years after it started production of molten metal. The giga steel developed by POSCO is cheaper than aluminum but it is three times stronger than other materials. Accoridngly, it is expected to emerge as a next-generation material for cars. The giga steel also has an excellent formidability so it can create lightweight but strong car bodies.
POSCO held a ceremony marking the completion at the No. 7 Continuous Galvanizing Line (CGL), which can galvanize the giga steel, an ultrahigh-tensile strength steel rated at 1.5 gigapascal, at the POSCO Gwangyang Steelworks on April 26. The ceremony was attended by some 250 people, including Chairman and CEO Kwon Oh-joon, South Jeolla Province Governor Lee Nak-yeon, Gwangyang City Mayor Jeong Hyun-bok, and officials from customer companies and equipment suppliers. The factory took 255.4 billion won (US$225.62 million) in investment and can produce some 500,000 metric tons of giga steel per year. POSCO also succeeded in reducing investment costs and securing the price competitiveness by designing and constructing the plant itself.
POSCO’s self-developed giga steel sheet has ultrahigh-tensile strength that can withstand over 100 kilograms per square millimeter. The name “giga” steel comes from its high tensile strength. It takes tensile strength of more than 980 megapascals for the galvanized steel sheet to split apart when pulled from opposite ends. A 10-by-15-centimeter giga steel plate can withstand 1,500 midsized cars that weigh about a ton each. The No.7 CGL is the world’s first plant that produces both galva-annealed (GA) and galvanized Iron (GI) car steel sheets rated at 1.5 gigapascal.
Since the GA steel sheet is plated in the form of an alloy of iron and zinc when galvanizing, it has an excellent coating and weldability, gaining popularity from Asian automakers, including Korea and Japan. The GI steel sheet, which has an excellent corrosion resistance as galvannealed coating layers cover the overall steel sheet, are preferred by European automakers.
Until now, only global leading steel makers have been able to produce giga GA and GI steel sheets rated at 1.2 gigapascal due to surface and quality problems caused in the rapid cooling process after plating. POSCO has solved the problems by developing its own “high hydrogen rapid cooling technology”, which forms high-intensity tissues in steel sheets before plating, and “rapid cooling facility,” which make plating surface beautiful through quick cooling after plating.