الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 99 |  |  |
| | | from | 99 | | |
Abstract
Ferritic-bainitic multi-phase steels are of great interest as a means of cutting the cost of steel
production and opening up the window of high mechanical properties. Almost all researches
in this field were done at laboratory scale. In the present work, online industrial runs to
produce ferrite-bainite steel using the hot strip mill (HSM) containing six stands at EZDK Steel
have been carried out.
Starting with low carbon steel composition (0.17% to 0.19% C, 0.54% to 0.83% Mn, and
0.015% to 0.63% V), the effects of chemical composition and hot-rolling schedule on the
considered 5 scenarios of ferrite-bainite and ferrite-pearlite steels were studied through
testing the mechanical properties and microstructures of the material.
The first consideration is the comparison between 3 different ferrite-bainite steels and how
the vanadium microalloying affected the final properties. This revealed that the mill is
capable of producing ferrite-bainite steel and that vanadium microalloying has affected
mechanical properties with different degrees in ferrite-pearlite and ferrite-bainite steels.
The second consideration is the comparison between ferritic-bainitic steels with ferriticpearlitic
steels of similar chemical composition. This revealed up to 27% (~100 MPa)
improvement in yield strength, 8% (42 MPa) in tensile strength, 13% in total elongation, and
11% (27 J) in impact toughness. This improvement is mainly due to bainite lath morphology
and fine grain size.
The third consideration is the production cost cut that is viable by replacing conventional
steel with ferrite-bainite steel (which can reach 56% when compared to low carbon Nb
microalloyed steels).