Steels_ Metallurgy and Applications, Third Edition

Low-carbon structural steels 167

0 .....

08

c, ~ ~" 0o,,o OOOOO ~ ~ oo O

"~ ~" ~.60 ~ ..... .. ~ o ~

~.- o 8

C ~ 2 0 .......

o

o

I |, ,

o Calcium-treated

9 Not calcium-treated

I

~A

0.010 0.020 0.030

Sulphur content (%)

0.040

Figure 2.16 Relationship between the sulphur content and the mean values of reduction
of area of tensile test specimens in the through-thickness direction of steel grade FG 36
(After Pircher and Klapdar iT)

beneficial effect of a reduction in sulphur content and calcium treatment on the
reduction in area in the through-thickness direction is shown in Figure 2.16.

Ships

Although there has been a significant decline in the world's output of new ships
since the mid-1970s, the production of large merchant vessels remains a major
application for structural steels. Despite marked changes in material selection for
other forms of transport, steel remains virtually unchallenged for hull construction
in large tankers and carders. However, like other forms of steel construction,
shipbuilding has witnessed the following changes since the early 1940s:

1. The change from riveting to welding as the principal method of joining.


2. An appreciation of the need for high levels of toughness.


3. The adoption of higher strength steels for reduced construction costs or higher
   operating efficiency.

Standard-strength steels

The main specifications for shipbuilding materials are issued by organizations
known as Classification Societies, namely:

9 American Bureau of Shipping
9 Bureau Veritas
9 Det Norske Veritas
9 Germanischer Lloyd