HOT TENSILE DEFORMATION1 OF ULTRA HIGH PURITY IRON BASE ALLOYS CONTAINING Al, N, S ON COOLING TO TEST TEMPERATURES

摘要

The problem of surface cracking in continuously cast steel slabs has been extensively investigated in the last few years by carrying out simple tensile tests'in the laboratory at the temperatures ranging from lower austenite phase to α + γ duplex phase regions (1-4). Low carbon steels usually present ductility troughs at these two regions. The low ductility in the austenite region has been attributed to the compositional effects and in particular to the formation of AIN (5), NbCN, VC (6), etc. precipitates at the grain boundaries. Several mechanisms of embrittlement have shown that these precipitates serve as cavity nucleation sites or prevent the occurrence of softening processes such as grain boundary migration and dynamic recrystallisation.