Steel is the most widely used material in shipbuilding, comprising about 90% of materials. The key properties materials must have include strength, weldability, toughness, resistance to marine corrosion, formability, and cost effectiveness. Various grades of steel are used - Grade A for thinner structures, Grade B for medium thickness, and Grades D and E for thicker, high-stress areas. Materials used in sea water systems include 90/10 cupro-nickel, which is resistant to corrosion and clogging, and stainless steel, which requires regular cleaning to prevent pitting. Expected lifespans are 6-9 years for galvanized steel and over 10 years for cupro-nickel alloys.

1. MATERIAL USED
foR SHIPBUILDING

2. INTRODUCTION
 There is a wide range of materials used in
shipbuilding comprising ferrous metals, non- ferrous
metals, plastics, GRP (Glass Reinforced Plastics/
fiber glass) and wood.
 The most widely used material in ship building
remains steel especially plan carbon or mild steel
approximately 90%.

3. Parts of a ship

4. Material issues relating to
construction of ship
 Strength
 Weldability
 Toughness
 Marine Corrosion
 Formability
 The Cost

5. Strength
There are 3 main types of stress:
Tensile / Tensioning
Compressive / Compression
Shear
to handle both loading scenarios (stiffness and
ultimate strength, based on length)

6. Weldability
Welds in a ship structure are also very critical to its 
overall strength, durability, and toughness. Even small
defects in weldments can create the initiation point
for considerably larger cracks and eventual failure

7. Toughness
must be able to deform plastically to some extent,
and tolerate cracks and flaws while maintaining
overall structural integrity

8. Marine Corrosion
There are various materials options, design strategies, 
coating, and cathodic protection technologies
available to the designer and shipbuilder

9. Formability
formability of the grade impacts toughness,
weldability, and strength

10. The Cost
Choosing the cheapest material in the construction
phase cannot be a considered a success if the
decision requires a significant increase in
construction labor or creates a maintenance
nightmare during the 30 to 50 year

11. Properties of Steel
 Good metallurgical properties – to
overcome Brittle fracture and fatigue
 Reasonable good mechanical properties
Low carbon steel (mild steel) have tensile
strength of 400 to 490 MN/m2
and Yield
strength of 235 MN/m2
, and elongation of
15 to 20 %
 Susceptibility ease to join process by
welding with good control over weld
defects
Cont-

12.  Reasonable cost
 Reasonably ease to cast
 Ability to be heat treated. Alloy elements can
also be use to change the character of steel:
- Carbon (0.18% to 0.28%) increases hardness
and strength but reduces ductility.
- Manganese (0.6% to 15%) increase tensile
strength, ductility and notch toughness
- Silicon (< 0.5%) increase hardness and tensile
strength without making welding difficult.
- Sulphur (>0.04 or 0.05%) improves weldability
and welding stresses
- Phosphorus (> 0.04 or 0.05%) reduces ductility
and toughness

13. Grades of steel
 Grade A - White
 Grade B - Green
 Grade D - Red
 Grade E - Yellow
Cont-

14. Grade A
 A mild steel used in the majority of the ship
structures of less than 20 mm thickness
such as bulkheads, tank top, non strength
decks and superstructures

15. Grade B
 A mild steel used for strength members of
20 to 25 mm thickness

16. Grade D
 A ‘Notch-tough’ steel which resists the spread of
cracks and has higher strength.
 It is used for structure greater than 25 mm thick

17. Grade E
 An ‘Extra Notch tough’ steel because this is a
heat treated Grade D steel used for very thick
plating in excess of 50mm thick.
 It is used for sheer strakes, bilge strakes, keels I.e.
all high stress regions of the ship

18. Artic D
 A special grade of steels used where part of the structure is
subject to extremely low temperature.
 The Ultimate tensile strength is 435 to 510 NM/m2
, yield stress
is 310 NM/m2
– 80% of UTS and absorbs 40 Joules of energy at
- 55o
C in a Charpy Impact test. Normally used for
icebreakers

19. Materials used in ships sea water systems
90/10 Cupro-nickel:
1. Resistant to high sea water velocities allowing
reduced tube diameters
2. Resistant to corrosion under stagnant flow
conditions and pitting
3. Resistant to clogging from marine growth
4. Ease of manufacture and welding
5. Reasonable cost

20. Stainless steel
1. Suffers from deep pitting in stagnant waters-if cleaned
regularly this pitting can be reduced

21. Expected life spans of some
materials in sea water:
 Galvanised steel- 6 to 9 years
 Copper- Maximum velocity (water flow) 4ft/sec
 90/10 Cupro-Nickel- 10yrs+
 70/30 Cupro-Nickel- 22 yrs+