Effect of Ti on Austenite Grain Growth Behavior in High Carbon Steels

Austenite grain growth behavior of two high carbon steels was observed using Confocal Laser Scanning Microscope (CLSM). Apparent austenite grain sizes for different holding time under a series of temperatures were measured by employing linear intercept method. Experimental results showed that Ti-bearing steel exhibited a much sluggish growth rate compared with Ti-free counterpart, which was attributed to the pinning effect of Ti(C, N) nanoparticles with the size of 20 to 40 nm on austenite grain boundaries. Based on the research conducted by using Transmission Electron Microscope (TEM) observation and Thermo-Calc calculation, Ti(C, N) was confirmed to be the dominant phase at elevated temperature. Some models were introduced to predict the grain sizes of both steels. By comparison, the results predicted by the modified Gladman equation are found to be closest to the experimental results, which could be employed to predict accurately the austenite grain growth of high carbon steels.