Microstructure Evolution of Nb Containing Steel during Simulated Hot Charging

摘要

The method to avoid the formation of hot cracking in hot charging process is analyzed in this paper.The microstructure evolution of Nb containing steel during hot charging process was investigated by simulation with a HT-1600 pipe furnace.The results indicate that the microstructure varied from y→γ+α→α+P with the charging temperature decrease from 950°C to room temperature,and the duplex phase of austenite and ferrite appeared at 750°C.Microstructure of the specimen at the beginning of rough rolling is austenite and the grain size is similar when the reheated temperature is above 850°C.Furthermore,severe mixed grain structure with coarse grain is apparent during the hot charging temperature from 750°C to 650°C.The hot charging temperature close to A1 and hot charging at 550°C is appropriate for saving energy and avoiding slab surface cracking in heating fumace.