Automobile recalls hit another record last year as stronger government enforcement and widening recalls of exploding air bags pushed the total above 51 million vehicles. The 2015 number barely beat the old record set in 2014, after that total was adjusted downward from nearly 64 million to eliminate double counting in the massive recalls of air bag inflators made by Takata Corp., according to the National Highway Traffic Safety Administration. The agency recorded almost 900 separate recalls last year, beating the 2014 record of 803, the agency said.