Steels_ Metallurgy and Applications, Third Edition

62 Steels: Metallurgy and Applications

450

n 400

"10

.~ 350

>-

300

/

jr

/

f

J

/ f

~ S

II Hot rolled

o Continuous annealed 760~

9 B tch anneale

0.02 0.04 0.06

Vanadium content (wt%)

Figure 1.67 Variation of yield stress with vanadium content of hot-rolled and batch-
and continuously annealed steel also containing 0.06 wt% P and 0.05 wt% Si (After
Pradhan l~

5O0

:[

-o

>.. o Continuous annealed, 760~

9 Batch annealed, 650~

0.02 0.04 0.06

Niobium content (wt%)

Figure 1.68 Comparison of the effect of continuous and batch annealing on the yieM
stress of cold-rolled niobium steels also containing 0.06 wt% P and 0.5 wt% Si (After
Pradhan 1~

1.68 and imply that titanium gives more strengthening per unit addition than
niobium.
It is sometimes necessary to supplement the strengthening from grain refine-
ment by strengthening from solid solution elements if a relatively high strength
is required in a cold-rolled and annealed product. The resulting steel, however,
has the general forming characteristics of a micro-alloyed steel rather than of a
solid solution-strengthened steel because the presence of the precipitates leads to
low r values.
Cold reduction is an important variable for micro-alloyed steels because it
influences both the temperature required for complete recrystallization and the
strength. After continuous annealing for one minute at 760~ for example, an
increase in cold reduction from 50 to 70% for a niobium steel decreases the