Metadynamic recrystallization and microstructure evolution of a continuously cast Ti-microalloyed steel slab with heavy reduction

Warm deformation is one of the promising hot rolling strategies for producing thin hot rolled steel strips. A better understanding of the microstructure evolution during warm deformation is important for a successful introduction of such processing into the industrial production. In the present research, the effect of deformation strain on the ferrite microstructure development in a low carbon Ti-microalloyed steel was investigated through warm torsion testing. Microstructural analysis with optical microscope and electron back-scattering diffraction was carried out on the warm deformed ferrite microstructures. The results show that at the early stage of deformation an unstable subboundaries network forms and low angle boundaries are introduced in the original grains. Then, with further straining, low angle boundaries transform into high angle boundaries and stable fine equiaxed ferrite grains form. It was considered that dynamic softening and dynamically formation of new fine ferrite grains, with high angle boundaries, were caused by continuous dynamic recrystallization of ferrite.

Download Full-text

Microstructure evolution in cold rolled strips during continuous annealing - modelling and simulation

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:2004120070 ◽

2004 ◽

Vol 120 ◽

pp. 607-614

Author(s):

V. Hein ◽

H. Freydank ◽

U. Michel ◽

H. Zieger ◽

G. Zouhar ◽

...

Keyword(s):

Microstructure Evolution ◽

Microalloyed Steel ◽

High Strength ◽

Experimental Simulation ◽

Rolled Strip ◽

Continuous Annealing ◽

Limited Temperature ◽

Cold Rolled ◽

Temperature Time ◽

Continuous Annealing Furnace

The empirical optimization of technologies for continuous annealing of cold rolled strips is very time, material and cost intensive. The properties of cold rolled strips demanded by the customer are adjustable only in relatively closely limited temperature - time regimes. Therefore, it is a complex task to increase the performance of continuous annealing furnaces without disadvantages for the product quality. This problem can be solved by nume-rical modelling the microstructure evolution in the cold rolled strip during continuous annealing combined with experimental simulation of the annealing process. At the Institut für Werkstoffwissenschaft, Technische Universität Dresden, in co-operation with EKO Stahl GmbH, Eisenhüttenstadt, a computer program signed as TFB was deve-loped. It is suited for modelling and simulating the recrystallization kinetics in cold rolled strips during continuous annealing. Furthermore, this program can be used for optimizing the annealing technology. For example, for IF steel the pre-sent paper demonstrates to what extent the performance of a continuous annealing furnace can be increased. Further results concern the improvement of the microstructure of the high strength microalloyed steel ZStE 380 Z by optimizing the annealing technology by means of experimental simulation.

Download Full-text