Abstract: The dynamic recrystallization behaviors of high performance bridge steel with lower Ni， Cr， Cu and Mo contents were investigated using single pass compression tests. At the same time， the true stresstrue strain curves were fitted and smoothed using a ninthorder polynomial in order to eliminate fluctuations in experimental curves， and the strain hardening rate vs true stress curves under different conditions were determined. The characteristics of the strain hardening rate vs true stress curves show that the dynamic recrystallization has occurred for different hot compression deformation processes studied. The constant α was modified as 0009MPa-1， the dynamic recrystallization activation energy was gained， the relationship of εc =063εp was determined and the critical strain model for predicting dynamic recrystallization initiation was established. Moreover， the dynamic recrystallization activation energy was significantly lowered with reducing Ni， Cr， Cu and Mo contents.

Key words: high performance bridge steels, thermosimulation, dynamic recrystallization, activation energy, critical strain