Influencing Factors of Nb-Ti Treated ULC-BH Steels’ Bake Hardening Property

Abstract

The precipitate in ULC-BH steels was analyzed by the phase analysis, the expressions for calculation of solution C content in the ULC-BH steel treated by Ti and Nb was developed. The test result indicates that the BH2 value was improved with the increasing of solution C content. The BH2 value can be improved by enhancing the temperature of annealing and cooling rate. The steel has higher BH2 value when the coiling temperature was 640℃ compared with 710℃ and the annealing temperature and cooling rate have more effect on bake hardening value than coiling temperature.