Characteristics of Austenite Transformation During Post Forge Cooling of Large-Size High Strength Steel Ingots

Numerical Simulation of Water Quenching of Large Size Steel Forgings: Effects of Macrosegregation and Grain Size on Phase Distribution

“…For distances of 200 mm or above from the surface of the sample, bainite volume fractions were very similar in both simulations. This could be explained in terms of the precedence of bainite transformation over martensitic transformation at slower cooling rates (i.e., far from the surface zone) as also reported by other authors through experimental work on similar steels [10,29,30].…”

“…However, most of them have been focused on calculation of Continuous Cooling Transformation (CCT) diagrams and hardness uniformity [7,9]. Time Temperature Transformation (TTT) or CCT diagrams are important tools to predict microstructure evolution during quenching by allowing the identification of phase boundaries of ferrite, pearlite, bainite, and martensite as a function of cooling rate [10]. In addition to the cooling rate, phase domains and boundaries are also influenced by grain size and chemical composition whether local or global.…”

“…A combination of Avrami [11] model, Koistinen-Marburger (K-M) equation [12] and Scheil additivity rule [11][12][13][14][15] have been used to predict phase transformation start and finish temperatures, residual austenite, bainite and martensite transformations as well as grain size variations and carbon content during the cooling process. However, little information is available on the influence of chemical heterogeneity and grain size variation on the volume fraction of the phases during the cooling process of large-size forged blocks [10,13]. Experimental determination of the volume fraction of phases during water-quenching of large blocks is not always possible due to the difficulty of obtaining samples from different sections of the forged slab.…”

In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

“…The as-quenched microstructure is comprised of bainite, martensite, plus some retained austenite [3][4][5]. The transformation of austenite to bainite and martensite during quenching is dependent on the cooling rate, chemical composition of the steel and prior austenite grain size and can be predicted by continuous cooling transformation (CCT) diagrams [3,6,7].…”

“…The transformation of austenite to bainite and martensite during quenching is dependent on the cooling rate, chemical composition of the steel and prior austenite grain size and can be predicted by continuous cooling transformation (CCT) diagrams [3,6,7]. The as-quenched microstructure will then rely on the mutual influences of the above factors.…”