| Popis: |
In this study, the effect of cold rolling on the recrystallization, grain growth of ferrite and the austenite formation in 0.14C–1.98Mn steel is studied extensively with different intercritical annealing times and temperatures.The starting sample is a 2,8 mm thick ferritic, pearlitic sheet. Samples are cold rolled to either 1,12 mm, 1,56 mm or 1,92 mm thicknesses. In order to see the changes in the microstructure below and within the intercritical temperatures, samples are annealed for 5 min and 10 min at different annealing temperatures and then quenched in water. Finally, the as-received sheet samples are annealed at the same temperatures for either 5 or 10 min in order to be able to compare the microstructural and mechanical property differences between cold rolled and not rolled samples.It is found that medium cold reduced (45%CR) samples have the lowest tensile properties at the middle-intercritical annealing range due to faster recrystallization and grain growth of ferrite. The effect of recrystallization and recovery is most pronounced at the onset of the Ae1 temperatures for all the samples. Due to higher recrystallization temperature, reduction of yield and tensile strength of 30% CR samples at low temperatures is the lowest. At high intercritical temperatures, the effect of cold rolling is lost due to very fast austenite formation. Additionally, the effect of cold rolling on the recrystallization and austenite fraction is observed in detail. FESEM study of the samples showed that austenite nuclei prefer the primary ferrite grain boundaries either adjacent to ferrite or pearlite. |
