* Ships are converted oil tankers with 300,000 dwt capacity
* Long-term leasing of ships part of strategy
* Sale frees up capital for Vale
SAO PAULO, Aug 31 (Reuters) - Brazilian miner Vale signed an agreement to sell 10 large iron ore carriers for $600 million to Polaris Shipping Co Ltd, and will instead lease the vessels, it said on Friday in a filing.
The world's second largest mining company acquired the 300,000 dead-weight-tonne vessels in 2009-10 to build up its fleet of ore carriers as part of a plan to limit its exposure to uncertainty on the global shipping market.
Today, the company ships about 70 percent of its iron ore in its own vessels or those under long-term contract, which gives it greater control over pricing, especially on the Chinese iron ore market. China is the world's largest steelmaker.
The sale of the ships under leasing contracts with Polaris frees up capital for Vale, while assuring it still has control of delivery of iron ore to its clients. This has been part of the company's strategy for nearly half a decade and was implemented under the former chief executive, Roger Agnelli.
The strategy was adopted after the 2008 financial crisis when shipping companies in Vale's biggest client, China, stopped sending vessels to receive ore that was then under annual delivery contracts to steel mills.
Chinese steel companies also used freight costs as leverage in ore price negotiations with Vale, which is at a disadvantage to its Australian rivals BHP Billiton and Rio Tinto due to the great distances between Brazil and China.
The 10 ships, which are converted oil tankers, are not part of the 35 Valemax or Chinamax class ships, which can carry over 400,000 dtw and have contributed to plummeting dry bulk shipping rates since they first started hitting the water. About 14 of the giant carriers have already been delivered.
The company is also securing 16 of the Valemax ships under long-term leases, contracts which are put up as collateral to finance the building of the vessels by third party shipping companies. The remaining 19 Valemax are operated by Vale.