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Abstract
Abstract:
The present study aimed at improving the formability properties of low carbon steel sheet, cold-rolled annealed sheet steel, for deep drawing purposes, through the optimization and control of process techniques in steel industry during cold rolling, batch annealing and skin pass rolling. Since optimum cold reduction % is at about 70%- 75%. Moreover, It was found that the annealing regime contains of two stages; intermediate anneal followed by further heating at final annealing temperature is better than that contains one step used in steel industry.
A number of double stage annealing regimes were investigated at different heating rates since heating rate in the first stage of annealing regime up to 600°C with heating rate ranging at [75-50 C°/hr] and soaking time 4 hrs while second stage from 600°C to 690°C with heating rate ranging at [20- 30 C°/hr] and soaking time ranging 9-12 hrs represent the main difference between various annealing regimes. Such difference is expected to play a role in the final microstructure features, such as grain size and aspect ratios.
The first step in annealing regime provides the precipitation before recrstallization commences and the second one brings about recrystallization. Therefore, helping to develop the pancake microstructure with the sharp recrystallization texture oriented to {111} <110>components. These results correlated well with formability parameters like, strain hardening coefficient (n), normal anisotropy (r - value) and planar anisotropy (∆r). Good formability requires high value of r- value, high n value and lower ∆r. Finally skin pass rolling improves the properties by eliminating the yield point elongation thus avoiding the stretcher strains or lauder bands in the subsequent forming process.
Key words :
Formability Properties ,Cold rolling, Batch annealing, Skin pass rolling, Deep drawing, Aspect ratio , Grain size , Recrystallization, Precipitation, Pancaked ferrite microstructures , Texture, Normal anisotropy, Strain hardening coefficient, Planar anisotropy , Stretcher strains, Lauder band.