关键词: 微合金化, TMCP工艺, 未再结晶区, 晶粒细化, Q460qE

Abstract: The Nb+V+Ti microalloyed Q390C continuous casting slabs were upgraded successfully to Q460qE via TMCP (thermo-mechanical controlled process) with all mechanical properties up to the relevant plate standard. The main parameters of rolling schedule in two pilot tests were as follows: rough rolling temperature range 1000-1100°C; finishing rolling onset at (890±10)°C and terminating at (820±10)°C; starting temperature for cooling is at (780±10)°C and ending at (630±10)°C, cooling rate about 12°C/s and the total reduction in finishing section not less than 60%. The cumulative heavy reduction in the austenite unrecrystallized region benefits the formation of high-density austenite grain boundary, thus increasing the ferrite nucleation rate with grain refining. Furthermore, it was found that the surface structure of the steel plate thus rolled is composed of tiny polygonal ferrite plus bainite and that the structure of intermediate layer is composed of ferrite plus pearlite. Such a structure can provide high tensile strength and impact toughness.