Page 86 - Ship Construction.DJ Eyres 6Ed

Ch09-H8070.fm Page 75 Wednesday, October 18, 2006 7:36 AM

9
Welding and Cutting Processes

used in Shipbuilding
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Initially welding was used in ships as a means of repairing various metal
parts. During the First World War various authorities connected with ship-
building, including Lloyd’s Register, undertook research into welding and
in some cases prototype welded structures were built. However, riveting
remained the predominant method employed for joining ship plates and
sections until the time of the Second World War. During and after this war the
use and development of welding for shipbuilding purposes was widespread,
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and welding totally replaced riveting in the latter part of the 20 century.
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There are many advantages to be gained from employing welding in ships
as opposed to having a riveted construction. These may be considered as
advantages in both building and in operating the ship.

For the shipbuilder the advantages are:

(a) Welding lends itself to the adoption of prefabrication techniques.
(b) It is easier to obtain watertightness and oiltightness with welded joints.
(c) Joints are produced more quickly.
(d) Less skilled labour is required.

For the shipowner the advantages are:

(a) Reduced hull steel weight; therefore more deadweight.
(b) Less maintenance, from slack rivets, etc.
(c) The smoother hull with the elimination of laps leads to a reduced
skin friction resistance which can reduce fuel costs.

Other than some blacksmith work involving solid-phase welding, the
welding processes employed in shipbuilding are of the fusion welding type.
Fusion welding is achieved by means of a heat source which is intense
enough to melt the edges of the material to be joined as it is traversed along
the joint. Gas welding, arc welding, and resistance welding all provide heat
sources of sufficient intensity to achieve fusion welds.