FIELD OF THE INVENTION:
This invention relates to an ultra high strength steel from
m ar t e n 51t e mi c r c = t r u c t u r e.
BAGKGROUND OF THE INVENTION:
The flourisr.ing of the automobile industry leads to newer
ways of meeting its growing requirements, Each day vith the
sudden rise m the manufacture of automobiles, -.here is
growing competition to adapt the models to suit :.ne fuel
resources, economy, road conditions and thereby improve the
overall efficiency of the cars. This necessitates an
increased emphasis on the development of new advanced
qualities of steel vitn greater strength,
OBEJECTS OF THE INVENTION:
It is an object of this invention to propose a high
strength steel to increase the strength to weight ratio of
autoinoDiies.
This and other obiects and advantages 01 this invention
will be more apparent from the ensuing description.
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DESCRIFTIOH QF THE INVENTION:
According to this invention is provided a high strength
carbon-manganese silicon steel with VS: ~ 950 Mta, UTS: -
1100 Mt'a and Elongation : - 12%.
According to this invention is further provided a process
lor the production ox nigh strength steel comprising
providing hot rolled carDon-manganese-siiicon steel o±
martensitic structure, subjecting the same to cold rolling
to aiiierent percentage ox reduction starting from /G to
85% to provide the cole roiled material, followed .oy
subjecting the cold roiled material to recrystallisation
annealing to provine the ultra high strength steel.
The steel usea lor the purpose is a carbon mangariese-
silicon steel, navmg the toiioving composition nn wt%s :
C:0.1-0.3 P:0.02 or less
Mn:1.5 or less T1:0.01 or less
S1:0.50 or less V:0.2 or less
S:0.015 or less Or: 0.1 or less
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Tr.e steel uith the above compositiori IH made in the air
induction furnace and subsequently forged at 9OO-11UU°C
with different amount of deformation and temperature at-
tach stroke to achieve homogenized microstructure. The
forged material 15 nor rolled and the FRT IS kept just
above AT3 temperature. The steel is then air cooled. The hot
rolled structure is observed to be ferrite-bainite. After
that the material is reheated at -900°C for i hr and water
quenched form that, temperature to produce martensite.
Martensite inherently 13 a line grained structure:. This is
the basic reason for selecting martensite as A starting
microstructure so that after final processing the steel
will yield ultra line grain structure. The hot rolled
material is then cold rolled to different percentage of
reduction starting from 20 to 85:%. The cold rolled material
is then subjected to annealing at various temperatures
ranging frcm 2OO0C to 7000C tor 20-t0 mins. This has given
a property of XXX- - 1100 MPa and % elongation of around 12%
after final processing.
Dated this 11th DAY OF JUNE, 2007.
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