The offer is valid between October 22 and November 11. Mittal Steel Holdings offered to pay 55 lei per share for some 2.83 million Comvex shares.
ArcelorMittal holds a 35.99% stake in Comvex via Expert Placement Services LTD. Under Romanian legislation, owners of more than 33% of a listed company are required to make a buyout offer to the other shareholders.
Comvex stock last traded at 51.1 lei, down 5.37%, by 0705 GMT on Friday on RASDAQ.
(1 euro = 3.6865 Romanian lei)