Lec ture 3 4 Adva nces i n Cont inuous Casti ng of Steel
Contents
Intr odu ction
High speed slab cast ing
Thin sl ab cas ting
Key words: Thin s lab ca sting, strip cast ing, Hot rolling , direct char ging
Introduction
Continuous casting is o ne of the mos t significant develop ments in the technology of steelm aking. A
ladl e cont aining 300 to ns of m olten stee l at 1600 can be cast into ap proximatel y 60 minut es in a
semi-fini shed produ ct like bl oom, b illet and slab. It reduces energy consumption, material han dling
and as a r esult lead to increa se in plant p roductivity. In addi tion continuous cas ting offers t he
possibi lity t o integrat e the h ot strip or bloo ming mill by direct hot charging. In recent years
conside rable developments have taken pla ce bot h in co nventional co ntinuous casting to improve
the pro duct quality and to dev elop n ew tech nology to produc e nearl y fini shed products. So me of the
developments are briefly described.
Electromagnetic Stirring(EMS)
EMS is a n elect ric met hod of inducing motion in liq uid ste el without using any mechan ical device. In
continuous casting EMS can be applied in mo ld and sec ondary cooling zone to
Decreas e segregat ion an d porosity
Improve steel cleanl iness by f orcing inclus ions to float on th e surfa ce where t hey can be
abso rbed by a slag
Improve the steel qu ality in term s of re ducing the defec ts
Stirrin g induced by EMS modifi es the flo w patt ern of molten steel of the solidi fying strand. Improved
stirrin g reduces segreg ation. Because of th e imposed stirring, the su perheat of the melt can be
quic kly di ssipate d whic h resul ts in modific ation of structure o f the solidif ying s trand f rom columnar
to equi axed a nd then to glo bular structu re.
EMS allows to increase the cas ting speed wh ich increa ses productiv ity of the caster.
An i nductive electro magnetic stir rer is the stator of an as ynchron omous moto r, the rotor of which is
the liquid core o f the solidifyin g stra nd. Thi s stator prod uces either a rotating or travelling ma gnetic
field B , whic h induc es eddy cu rrent J, perp endicular to B and its vel ocity v ector. B and J combine
togethe r to create a n electromagn etic force which cau ses st irring in the bath. The mains fre quency is
usua lly us ed for sti rring bill ets or small blo oms beneat h the mold . In secondary cooling zo ne low
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