Steels_ Metallurgy and Applications, Third Edition

Low-carbon strip steels 15

particular orientation. The spatial distribution of texture is important because
what happens to a particular subgrain in a material during recrystallization is
strongly influenced by the orientation and structure of the material around it. The
orientation of groups of neighbouring grains may be laboriously studied using
Laue diffraction photographs, but the recently developed technique of electron
backscatter diffraction 25 enables the orientation of neighbouring grains to be
studied more easily.
During cold rolling, the texture, which is often close to random in the hot band
structure, develops progressively with increasing cold reduction, as illustrated
by means of inverse pole figure data in Figure 1.11. An equivalent plot, by
means of two fibre lines through an orientation distribution function, is shown
in Figure 1.12. This figure gives the intensities along both the alpha and gamma
fibres. Clearly both fibres become stronger with increasing cold reduction due
to the progressive rotation of the orientation of grains from other orientations
into these two fibre orientations. The precise intensities along the fibre groups
of components depend on the type and details of the steel and there is also a
marked effect of hot band grain size.
The other important effect that occurs during rolling is the development of a
deformation structure. As deformation proceeds, the dislocation density increases,
but there is a tendency for dislocations to cluster together. The final result after
sufficient deformation is that a subgrain structure is formed with a high disloca-
tion density in the subgrain boundaries and a relatively low density within the
subgrains. 2s The total stored energy of deformation depends on the total mean
dislocation density. It depends, therefore, on the subgrain size and the orienta-
tion difference between adjacent subgrains since the latter is determined by the
dislocation density within the subgrain boundaries.
It was indicated previously that iron may have a face-centred cubic or a body-
centred cubic form. When either of these two crystalline structures is deformed,
the deformation can take place by dislocation movement only on particular slip

i n l i Lll || | i i .......

Oo

-. ,,d" (111)

i "

6 Os

9 0

41. ." ,o e 1001)1
    ~- ,o" 9

0 9 ,,oo. I,el o le.

0 20 40 60 80 100

% Cold reduction

Figure 1.11 Variation of the intensity of the components of the deformation texture of

aluminium-killed steel with cold reduction (Held 26)