Steels_ Metallurgy and Applications, Third Edition

174 Steels: Metallurgy and Applications

Table 2.12 Steel selection in merchant ships

(a) Material classes

Structural member Material class

Within

0.4L amid-

ships

Between

0.4L and

0.6L

amidships

Outside

0.6L

amidships

Where L > 250 m:
Sheerstrake or rounded gunwale
Stringer plate at strength deck
Where L < 250 m:
Sheerstrake or rounded gunwale
Stringer plate at strength deck
Bilge strake
Deck strake in way of longitudinal bulkhead
Strength deck plating
Bottom plating including keel
Continuous longitudinal members above
strength deck
Upper strake of longitudinal bulkhead
Upper strake of topside tank
Deck plating, other than above, exposed
to weather
Side plating
Lower strake of longitudinal bulkhead
External plating of rudder horn
Sternframe
Internal components of rudder horn
Rudder
Shaft bracket

V

IV

III

III

III

II

III

(b) Steel grades

Thickness, t

(mm)

Class

I II III IV V

MiM H. T. MiM H. T. MiM H. T. MiM H. T. Mild H. T.

steel steel steel steel steel steel steel steel steel steel

t < 15 A AH A AH A AH A AH D DH
15 < t < 20 A AH A AH A AH B AH E DH
20 < t < m 25 A AH A AH B AH D DH E EH
25 < t < 30 A AH A AH D DH E DH E EH
30 < t < m 35 A AH B AH D DH E EH E EH
35 < t < m 40 A AH B AH D DH E EH E EH
40 < t < 50 B AH D DH E EH E EH E EH
t > 50 B AH D DH E EH E EH E EH

After Lloyd's Register of Shipping, Rules and Regulations for the Classification of Ships. 19