TOKYO, July 31 (Reuters) - Nippon Steel Corp (5401.T: Quote, Profile, Research, Stock Buzz), the world's second-biggest steelmaker, said on Thursday it had agreed with mining group Xstrata (XTA.L: Quote, Profile, Research, Stock Buzz) on almost quadrupling prices for low-grade coal.

The contract price for low-grade coal will be hiked to $240 per tonne in the current business year against $64 last year, Nippon Steel said. (Reporting by Yuko Inoue)