1. Warm rolling of pure iron involves rolling the material in the ferritic phase region between room temperature and the austenite transformation temperature. This results in a two-phase microstructure of ferrite and austenite during deformation. 2. Solute carbon interacts strongly with dislocations during warm rolling, resulting in high strain rate sensitivity and reduced in-grain shear band formation compared to hot or cold rolling. This significantly impacts the development of texture and recrystallization. 3. Warm rolling can produce deep drawing {111} textures traditionally obtained through cold rolling and annealing. Process parameters in warm rolling therefore have a strong influence on recrystallization texture development.

1. Warm Rolling of pure iron
GERUGANTI SUDHAKAR
PHD(MATERIALS ENGINEERING),H.C.U

2. Grain Size Distribution
CHARACTERISATION OF MICRO-STRUCTURE :
OPTICAL MICROSCOPY

3. INTRODUCTION:
Most polycrystalline metals contain crystals which are not
randomly oriented in space, but rather, their axes are
approximately aligned with the macroscopic shape of the
sample. The non-random distribution arises because of ori-
ented processing, heat-treatment or phase transformation.
The sample is then said to be crystallographic ally textured and
exhibits macroscopically anisotropic properties, which reflect
the orientation distribution. Such anisotropy can be
advantageous. In ferritic iron, the magnetic flux density rises
most easily along <100>directions, in contrast to
<111>directions which are said to be magnetically hard.Iron
used for electrical transformer core applications involves rapid
changes in magnetic field therefore iron perform better in
terms of energy loss, permeability as well as magnetic flux den-
sity when the crystals are aligned with <100>directions par-allel
to the sheet normal. The {100} planes which contain two
perpendicular <001>directions
and no <111>direction are naturally the planes of easy
magnetisation, so a texture in which these planes are
aligned to the sheet surface with the cube edges
parallel to the sample axes is known as the cube
texture, {100}<001>.Typi-cal efficiency of motors
ranges from 83 to 92%, and their operating efficiency is
far below, 62% The only way to improve motor
efficiency is to reduce motor losses. Loss components in
an induction motor include core loss in iron cores, the
copper loss in rotors and stators, the stray load loss, and
the friction and windage loss.Among them,the copper
loss and the core loss, which cover at least 75 %of the
overall losses, can be reduced significantly by improving
magnetic flux density along with reducing iron loss
through the texture control of core materials.

4. Texture formation in metal alloys with cubic crystal structures; Texture Control During Manufacturing of Non-
Oriented Electrical Steels:
Texture study in materials science is in essence a
quantitative statistical study of crystallographic
phenomena that contribute to the shaping of
microstructure.
It filters out the relevant crystallographic orientations
that appear in solid-state transformation processes,
occurring during making and using of materials
The orientation of metallic crystallites after plastic
deformation depends on different parameters such as
1. chemical composition,
2. working temperature,
3. initial texture and
4. history of deformation.
In FCC metals, the dominant slip system is {111}<110> (at ro
temperature), whereas in BCC metals, the slip direction is
always<111> , but the slip planes can be {110}, {112} and,
perhaps {123}.
The typical texture of rolled BCC metals is composed of a
partial α-fibre (running from {001} to {111}) and a γ-fibre
(running from {111} to {111}), also known as RD-fibre and ND
fibre, respectively.
During plastic deformation individual grains in polycrystalline
materials fragment into regions of different orientation

6. 2. Development of Through-Thickness Cube Recrystallization
Texture in Non- oriented Electrical Steels by Optimizing
Nucleation Environment
Fig. —Schematic representation of
the formation of through-thickness
cube texture during primary
recrystallization:
(a) warm rolling microstructure,
(b) formation of cube grains at
the boundaries of deformation
bands with orientation in
Regions I and II in the early stage
of recrystallization, and
(c) formation of cube texture after
primary recrystallization
The formation of through-thickness cube recrystalliza-tion
texture is attributed to the optimization of nucle-ation
environment, featuring quantitative advantage of cube nuclei
at both SPS and SSS layers under the superiority of locally low
density of cube nuclei.

10. Effect of Strain Rate on Mechanical Properties of Pure Iron
Mechanical properties of pure iron under different strain rates
were studied. Strain rate hardening and work hardening were
analyzed. The results are as follows: (1) Yield stress increases
when strain rate increases from 10-3 to 8500 s-1, indicating
strain rate hardening effect. (2) It is a competitive result by
work hardening and thermal softening that flow stress first
increases and then decreases with increasing true strain at the
strain rate range from 6000 to 8500 s -1 . (3) Adiabatic
temperature rise increases with increasing the strain rate. (4)
There are only two work hardening regions in static stage while
there are three work hardening regions in dynamic stage due
to the onset of twining at high strain rates.

11. Cube Texture Formed in Biaxially Rolled Low-Carbon Steel;
The chemical composition of the investigated low-carbon steel
is 0.16C-0.37Si-1.39Mn. Steel blocks of 50×50×100mm3 were
cut from the as-received hot-rolled 50mm-thick slab in the
same dimensional arrangement. The steel blocks were then
forged at 1473K to 42×42×150mm3 , as the starting material of
the present research. In order to diminish the retained texture
caused by hot-rolling and forging, the samples were water-
quenched from 1373K and then tempered for 7.2×103 s at
923K, resulting in the randomly oriented ferrite and dispersing
cementite microstructure.

12. Pure Iron, one hour annealing at 700oC resulted in ferrite grain
size of 40μm, which were respectively 58 and 83μm for
annealing at 800oC and 900 oC for the same annealing time
period
Significant increase in ferrite grain sizes with annealing
temperature, Solid State diffusion rate of iron is a slow
process. However, with increase in temperature the diffusion
rate increases significantly
Increase in the annealing time periods resulted in a very minor
change in the ferrite grain size. However, increase in the
annealing temperature caused a significant ferrite grain
coarsening effect.
Samples were melted in vacuum by induction melting and
forged
Effects of Process Parameters on Ferrite Grain Size of
Commercially Pure Iron

14. phosphorus is a ferrite stabilizer. It retards the transformation
of ferrite to austenite during heating period. On the other
hand, during cooling period after solidification, austenite grains
could not grow sufficiently because of their early
transformation to ferrite. As a result, large numbers of ferrite
grains were formed in P-added iron. So, both Fe-P alloys
showed relatively finer ferrite grains. ompared to Fe-P-I alloy,
the P content in Fe-P-II alloy is nearly double. However, no
significant refinement in ferrite grain sizes was observed. The
possible reason is that the line connecting line of the lower
critical temperature points of Fe-P alloys containing P between
0.1 (point A) and 0.2% (point B) is almost flat. This means lower
critical temperatures of Fe-P-I a nd Fe-P-II alloys were almost

15. Effect of Heating Rate on the Development of
Annealing Texture in Nonoriented Electrical Steels
Effect of Heating Rate on Texture in Coarse
grained Specimen
The average grain size decreases as the heating rate increases.
However, the difference in grain size between specimens heated
at 30°C/s and 10°C/s is negligible. The size of recrystallized
grain is determined by both the nucleation and growth rates.
During the annealing process, less recovery takes place during
fast heating than during slow heating so more stored energy is
preserved in the specimen heated by fast heating before
recrystallization commences. Higher stored energy increases the
nucleation rate faster than the growth rate As a result, the
annealing by fast heating leads to a smaller grain size than that
by slow heating.

16. Effect of Heating Rate on Texture in Fine-grained Specimen:
The textures are characterized by a strong g-fiber with a
maximum at {111}112, for all heating rates. However, the
intensity of the {111}112 component changes with increasing
heating rate and shows a significant difference between fast
heating and slow heating. The heating rate also influences the
development of the Goss component, and the Goss intensity
increases slightly with the increase in the heating rate
In the case of fast heating, a very strong {110}001 (Goss)
texture develops and its intensity is higher for a heating rate o
30°C/s than for 10°C/s. On the other hand, in the case of slow
heating, the {111}112 component is dominant

17. Conclusions
(1) The average grain size decreases with an increase in
the heating rate both in the coarse-grained and in the
fine-grained specimens.
(2) In the coarse-grained specimen, the Goss texture is
significantly strengthened but the {111}112 texture
component is slightly weakened as the heating rate
increases. On the other hand, in the fine-grained
specimen, the intensity of the {111}112 component is
greatly reduced but the Goss intensity is slightly increased
as the heating rate increases.
(3) The heating rate up to the annealing temperature
affects texture formation differently depending on the
grain size prior to cold rolling. These differences may be
related to the number of shear bands formed in the cold
rolled state.
Examination of the microstructure indicates that shear bands are
more likely to form in materials with a coarse grain size prior to
cold rolling
In the coarse grained specimen, fast heating greatly strengthens
the Goss texture but slightly weakens the {111}112 texture
whereas, in the fine-grained specimen, fast heating significantly
decreases the {111}112 texture but slightly increases the Goss
texture

18. Distinctive Aspects of the Physical Metallurgy of WarmRolling
Warm,or ferritic, rolling is gaining in popularity
amongststeel makersas a meansof cutting the cost of
steel production and opening up the windowof hot band
properties. the present review is organized under the
headings of: transformation, deformation and
recrystallization.
Warm rolling is often carried out such that the
microstructure during the final finishing passes is
composedof more than 90% ferrite. (For a 0.060/0 C
grade, the maximumwarmrolling finishing exit temperature
falls around 780'C. The flow stress of a ferrite/austenite
microstructure can beconvenlently described as a
weighted average of the individual flow stresses of the two
phases the situation for warmrolling is complicated by the
phasetransformation and, in the presence of solute
carbon, dynamic strain aging (DSA)

23. (i)
. Warmrolling often involves deformation and restoration
In the two-phase region. Hot rolling is confined
to austenite deformation and cold rolling to
worklng of the ferrite phase. The presence of a
second phase interferes with the deform'ation and
softening mechanismsof the primary phase, and vicc'
ve,"sa. This has not beengiven muchattention in the
literature and is an area requlring further work if
the microstructural evolution during warmrolling
Is to be accurately modelled
(ii) Solute carbon interacts with dislocations during
warmrolling in a mannerquite un]ike that seen
either in cold or in hot rolling. Thls occurs because
of the combination of high carbon mobility and the
strength of the C atom interaction with dislocations.
As a consequence, high strain rate sensltivitles and
low levels of in-grain shear band formation accompanythe
presence of solute carbon. The relatlve
absence of in-grain shear bands under these
conditions has a major impact on texture development
and recrystallization.
(iii) The effects of the shear strain arising from friction
forces in the roll bite on the texture are more
prominent than those seen in hot rolling. Thls
occurs for a numberof reasons. Firstly, there is no
transformation after rolling to randomise the
texture. Secondly, there is a greater chance of
accumulating surface shear strain during warm
rolling due to the ease of avoiding Interpass
recrystallization
whenusing lower rolling temperatures.
And thirdly, higher roll forces, and hence
higher friction forces, are possible in warm rolling.
(iv) Warmrolling maybe used to produce {i Il} deep
drawing textures. This has traditionally been the
domain of cold rolling and annealing. As a
consequence, Iittle indication existed previously as
to the likely impact of hot strip mi]1 rolling parameters
on the Intensity of the {11 l} recrystallization
texture of warmrolled strip.
The metallurgical issues stemming from these features
pose difficulties for the steel producer; nevertheless
they also open up new opportunities in process and
product optimisation