Boxing robots are the undisputed champions at the weekend box office. According to studio estimates Sunday, Hugh Jackman’s “Real Steel,” set in a near-future when robot fighters have replaced humans in the ring, debuted at No. 1 with $27.3 million. “Real Steel” added $22.1 million overseas for a worldwide total of $49.4 million. The movie casts Jackman as a former boxer reluctantly thrown together with his young son as they turn a junkyard robot into a world-class contender.