The influence of cooling rate on the hot ductility of plain C-Mn steels containing 0'1-0'7%C has been examinedfor tensile specimens tested in the temperature range 1000-550°C. Increasing the cooling rate from 10 to 60 K min -1 in all cases caused the ductility to deteriorate. This deterioration was found to be associated with the presence of a finer sulphide distribution in the ferrite surrounding the austenite grains, as well as a reduction in the thickness of the ferrite covering. Decreasing the strain rate from 3 x 10-3 to 5·3 X 10-4 S-l led to a smaller influence of cooling rate. However, ductility was always poorer at the lower strain rate as grain boundary sliding was enhanced. Evidence is also submitted to indicate that MnS inclusions can encourage the production of deformation induced ferrite, leading to an earlier recovery in ductility at the low temperature end of the trough in the hot ductility curve. MSTj3758The authors are in the

Tensile samples were cast in situ and cooled to test temperatures in the range 760 to 1100°C, at cooling rates of25, 60, and 200 K min -1 . In all cases, increasing the cooling rate to that undergone during thin slab casting caused the ductility to deteriorate. For C-Mn-Al steels this deterioration resultedfrom both afiner AIN precipitation as well as afiner dispersion of sulphides. In the case ofC-Mn-Nb-AI steels, the inferior ductility arose because increasing the cooling rate caused more Nb to be held in solution before testing so that more of the detrimental strain induced Nb(CN) precipitation could occur during the test.MST/3853The authors are in the

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