Effects of heat treatment and Si on mechanical properties of 0.1%C low carbon TRIP aided cold-rolled steel sheets containing Cu

摘要

The main emphasis of the present study has beenplaced on understanding the effects of heat treatment and Si onmicrostructures and properties of the low carbon cold-rolled TRIPaided steel sheets. Two kinds of O.1O%C-1.5%Mn-Si-O.5%Cucold-rolled steel sheets were prepared, and were intercriticallyannealed following isothermal treatment at bainitic region.Microstructural observation and tensile tests were conducted, andalso the volume fractions of retained austenite were measured. Thevolume fractions of retained austenite and the mechanicalproperties of the steel sheets were changed dramatically by heat-treatment conditions. The volume fractions of retained austeniteincreased with decreasing intercritical annealing temperature andisothermal treatment temperature, resulting in the improvement oftensile strength, elongation, and strength-ductility balance (TSXXElong.). In case of the ECO-5 steel sheet (high Si content), thehigher volume fractions of retained austenite and mechanicalproperties were obtained compared to the ECO-4 steel sheet (lowSi content). From the results of the present study, it is reached aconclusion that the conditions (temperature and time) ofintercritical annealing and isothermal treatment should beestablished in consideration of the stability of austenite with thesolubility of alloying elements in the austenite formed during theintercritical annealing.