Warren Buffett's Berkshire Hathaway Inc. will sell debt, in what may be the conglomerate's biggest bond sale, in part to repay a $10 billion loan used to finance its purchase of Precision Castparts Corp. Berkshire may sell the debt in up to eight parts as soon as today, according to a person with knowledge of the matter. Buffett had said earlier that Berkshire used about $23 billion of its cash for the deal and will borrow the rest.