Dual-phase steels for non-heat treated high tensile bolts

摘要

In the field of high-strength bolts (> 115000 PSI), boron-type steels such as 10B21 have replaced grades like C1038. This first step has allowed reduction of the manufacturing sequence by eliminating the need for a soft annealing before cold forming. The final properties of the finished product are still obtained by a conventional quenching and tempering treatment.In order to also suppress this final heat treatment, and thereby simplify considerably the processing steps, Unimetal has worked towards the development of dual-phase steels.In the as-rolled wire rod condition, these grades offer cold formability combined with work hardening to obtain tensile levels generally only reached by quenching and tempering.