Numerical simulations of gradient cooling technique for controlled production of differential microstructure in steel strip or plate

Abstract

<abstract><p>Numerical studies were conducted to investigate the applicability of cooling strategies for controlledly producing a microstructure in the steel strip or plate, which changes as function of the plate length. In the numerical simulations, the water spray cooling was varied as function of the plate length and as a result, the different parts of the plate were cooled at different rates. We applied the previously developed numerical code where the transformation latent heat is coupled with the heat conduction and transfer model, which has also been calibrated to correspond to experimental laboratory cooling line. The applicability of the method was investigated for controlledly creating alternating bainite and polygonal ferrite regions in plates of two different thicknesses (0.8 cm and 1.2 cm thick plates) by cooling different parts of the plate to different temperatures before switching off the water cooling so that polygonal ferrite forms in the part which has been cooled to higher temperature and bainite forms in the low temperature part. The simulation results indicate that the controlled production of such alternating regions is possible, but the resulting regions in the studied scenario cannot be very thin. The transition regions between the ferrite and bainite regions in the simulated cases are in the range of 5–15 cm. Controlled production of zones consiting of softer phase in the otherwise bainitic steel could offer a possibility for creating designed tracks in a steel bainitic strip or plate, where the mechanical working or cutting of the material is easier.</p></abstract>

Numerical experiments on the solution of advection equation for moving phase interface: Encountered problems and their solutions

“…For example, It has been recently shown that by applying local laser processing can enhance mechanical properties of achieved heterogeneous steel [1]. Previous experiments and numerical simulations [2] show that also differential cooling rates could be applied to controlledly create desired heterogeneous microstructure to the material. Furthermore, due to its effect on the mechanical properties, the microstructure development during processing [3][4][5][6] needs to be understood in detail in order to control it effectively.…”

In-Situ Sem Characterization and Numerical Modelling of Bainite Formation and Impingement of a Medium-Carbon, Low-Alloy Steel

“…We have previously developed a coupled heat conduction and mean field (MF) phase transformation model [14][15][16][17], that has been applied for simulating austenite decomposition in cooling of a steel coil [15] as well as in slow cooling of low temperature ausformed steel, which leads to the formation of fine bainitic structure [18]. The mean field phase transformation model has been also used for simulating microstructure evolution to aid the design of induction hardening of a medium carbon pipeline material [19] where the model can be used for optimizing the cooling path and strategy so that desired fractions of different phases can be obtained [20,21] through the pipe thickness. Using this model, it is possible to quantitatively estimate the phase fraction and final hardness.…”