Numerical Simulation of the Hot Rolling Process of Steel Beams

The complete rolling schedule (25 passes) of steel beams in a mill was simulated to predict the final beam length, geometry of the cross-section, effective stress, effective plastic strain and rolling power for two cases; the first case corresponds to the hot rolling process assuming a constant temperature of 1200 ∘C. The simulation of the second case considered the real beam temperature at each pass to compare the results with in-plant measurements and validate the numerical model. Then, the results of both cases were compared to determine the critical passes of the process with high peaks of required power, coinciding with the reports at the mill. These critical passes share the same conditions, high percentage of reduction in cross-sectional area and low beam temperature. Additionally, a potential reduction of passes in the process was proposed identifying passes with low required power, minimal reduction in area of cross-section and essentially unchanged geometry. Therefore, it is reasonable to state that using the present research methodology, it is possible to have a better control of the process allowing innovation in the production of profiles with more complex geometries and new materials.

Coupling Thermomechanical Processing and Alloy Design to Improve Textures in Mg-Zn-Ca Sheet Alloys

The effect of Ca and Zn additions on the microstructure and texture evolution during thermomechanical processing of Mg-Zn-Ca sheet alloys was systematically investigated and quantified. Plane strain compression testing in a Gleeble thermomechanical simulator was used to physically simulate a 10-pass rolling schedule, while allowing for careful control and monitoring of the processing parameters. Textures in the as-deformed ternary alloy samples demonstrate a weak maximum basal intensity and spreading in the transverse direction. Increasing the Zn content to 3.2 wt.% in the ternary alloys resulted in samples that exhibited weak textures in the as-deformed state. Importantly, static recrystallization (SRX) during post-deformation annealing of these alloys promoted a desirable annular texture, with the c-axis tipped from the normal direction and a lower basal texture intensity. The evolution in texture during SRX is associated with as-deformed microstructures with broad grain orientation spreads and a low degree of recrystallization.

Modification of Microstructure and Texture in Highly Non-Flammable Mg-Al-Zn-Y-Ca Alloy Sheets by Controlled Thermomechanical Processes

The influence of rolling temperature and pass reduction degree on microstructure and texture evolution was investigated using an AZXW3100 alloy, Mg-3Al-1Zn-0.5Ca-0.5Y, in wt.%. The change in the rolling schedule had a significant influence on the resulting texture and microstructure from the rolling and subsequent annealing. A relatively strong basal-type texture with a basal pole split into the rolling direction was formed by rolling at 450 °C with a decreasing scheme of the pass reduction degrees with a rolling step, while the tilted basal poles in the transverse direction were developed by using an increasing scheme of the pass reduction degrees. Rolling at 500 °C results in a further distinct texture type with a far more largely tilted basal pole into the rolling direction. The directional anisotropy of the mechanical properties in the annealed sheets was caused by the texture and microstructural features, which were in turn influenced by the rolling condition. The Erichsen index of the sheets varied in accordance to the texture sharpness, i.e., the weaker the texture the higher the formability. The sheet with a tetrarchy distribution of the basal poles into the transverse and rolling directions shows an excellent formability with an average Erichsen index of 8.1.

An Integrated Model for Rolling Schedule Design of Microalloyed Steels

Processing parameters have direct impacts on the quality of the steels produced. This is particularly true for microalloyed steels, the production of which involves a thermomechanical controlled rolling process, which combines multi-pass hot rolling with accelerated cooling. On one hand, hot rolling may finish below A3temperature when austenite starts to transform to ferrite. On the other hand, controlled cooling is applied to obtain the desired microstructure from austenite decomposition. To optimise the TMCP parameters of such alloys, not only a clear understanding of each metallurgical phenomenon involved is required, but also the interactions among them. This paper reports our recent work on modelling of microstructural evolution and deformation resistance during multi-pass hot rolling of steels. The model considers the following metallurgical phenomena as well as their interactions: - Precipitation of MX type carbides, nitrides or carbonitrides. - Interactions between precipitation and recrystallisation and their effects on grain refinement. - Effect of grain size and cooling path on transformations from austenite to ferrite, pearlite, bainite and martensite. - Effect of rolling parameters, recrystallisation and microstructure on the deformation resistance of the alloy. The model predicts the evolution of microstructural features such as precipitate size and amount, recrystallisation fraction and effective strain, grain size, and austenite decomposition, as well as the alloy’s deformation resistance during hot rolling. It has been applied to a wide range of steels and demonstrated good agreement with experimental observations. Therefore, it has the great potential to be implemented in a production line to help optimise the rolling schedule for both C-Mn and microalloyed steels.