EFFECT OF MN AND TI PRECIPITATES ON THE HOT DUCTILITY OF LOW-CARBON AND ULTRA-LOW CARBON-STEELS

Hot ductility and precipitation behavior of Titanium-bearing and titanium-free low carbon and ultra low carbon steels have been investigated by an elevated temperature tensile test and quantitative analysis of Ti, Mn and S precipitates. in the steel without titanium, the main precipitate was MnS in austenite, The amount of Mn precipitates increases as temperature is lowered until a saturation level, The ductile brittle transition temperature can be evaluated by the Mn/S ratio. Ductility can be improved by holding at 11OO degrees C or cooling-reheating process. On the other hand, in the titanium-bearing steel, the amount of Mn precipitates was very small due to Ti precipitated in austenite. The ducti le-brittle transition temperature corresponds to the amount of Ti4C2S2 precipitated, and the ductility cannot be improved by holding at 1100 degrees C or cooling-reheating process.