Nippon Steel Corp. and Sumitomo Metal Industries Ltd. merged Monday to form Nippon Steel & Sumitomo Metal Corp., becoming the world's second-largest steelmaker at a time of market uncertainty exacerbated by the strong yen.

Second only to Luxembourg's ArcelorMittal SA with steel production of 46.1 million tons a year, the merged companies together have more than 81,000 employees and posted annual sales of around ¥5.5 trillion in the fiscal year ended in March.

The launch of the new company is the first major alliance in the Japanese steel industry after the merger in 2002 of Kawasaki Steel Corp. and NKK Corp., which created JFE Holdings Inc.