National Aluminium Company Ltd (Nalco), the Navratna PSU under Union Ministry of Mines and country's leading manufacturer and exporter of alumina and aluminium has reported all-round improvement in production and sales for 2010-11. The company has achieved the highest-ever cast metal production of 443,597 tonnes, against the previous best of 431,488 tonnes in 2009-10. Besides, Nalco's alumina refinery has…