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TURMA: 3MA, 3MB
DISCIPLINA: ING 6
PROFESSOR : J ALMEIDA
MATERIALS USED ON SHIP CONSTRUCTION
Steel
Steel is still the most popular material for the construction of ships because of its:
-technical and economical benefits
strength
- suitability for welding
- adequate resistance to brittle fracture
- availability and low cost.
In the early stages of the design, it has to be established what kind of steel will be
used. The higher the tensile strength, the thinner the material can be, resulting in less
weight and a smaller displacement, or more cargo.
The making of steel
The various types of steel are made of iron (ore) and/or (steel-)scrap.
During the process, the basic materials are heated up to approximately 1,600°C after
which the refining process starts. During the process a number of unwanted elements,
such as carbon, sulphur and phosphorus are skimmed off as slag.
Depending on the type and quality of steel to be made, a refining process is chosen
(basic oxygen transformer, electrical furnace and open furnace process) and completed.
The differences in tensile strength, hardness and welding qualities are established by
adding special additives, such as carbon, silicium, manganese, nickel, chrome, etc. in
combination with heat treatment when making plate materials.
Steel classification
Most small ships, up to a length of approximately 80 metres are built of what is
commonly named steel 42.
The value 42 refers to tensile strength (measured in kg/mm2).
Instead of working with this tensile strength value, the yield value is used. The yield value
refers to the yield stress that the steel can handle.
Standard codes are used for this. 5235 and 5355 are two common steel types. 5235
has a yield stress of 235 N/mm2- This is the yield strength of steel 42. 355 N/mm2 is
the yield strength of Steel 52, now 5355 and what is called High Tensile Steel and has
a tensile strength of 52 kg / mm2.
Good properties for welding are very important and are dependent on the carbon
content, which has to be around 0.20%.
'Mild Steel' is a common name for the good weldable steel that is most used in
shipbuilding. 5235 and 5355 are both often called 'Mild Steel'.
Classification adds a letter to the yield value. This is A, B, D or E, which indicates the
given yield stress, or Charpy-V value, at lower temperatures. Higher values are obtained
by adjusting the content of carbon, manganese, phosphors, sulphur, silicon and aluminium.
Grade A is steel is used most. D or E is used when thicker material is needed.
MARINHA DO BRASIL
CENTRO DE INSTRUÇÃO ALMIRANTE BRAZ DE AGUIAR
SUPERINTENDÊNCIA DE ENSINO
