THE WELDING PROCESS –
Welding is a process of connecting metal parts by fusion. Arc
welding and ox-acetylene welding are the two usual methods
adopted. Molten or fused metal is deposited between the metal
parts which are to be connected. The metal parts are also
fused to a speciﬁed depth. When the deposited fused metal is
cooled, the metal parts get joined by new metal. The ends of
metal parts to be connected and the tip of the weld rod are
fused by arc which causes a high temperature of about 3300
degree Celsius. In the ox-acetylene method a jet of
burning oxygen and acetylene is used as a source of heat. The
weld rod has a coating which also melts during the welding
process and forms a shield preventing combination of the
heated metal with the freely available oxygen and nitrogen
from the atmosphere.
Fig. Gas metal arc welding (MIG
ADVANTAGES 0F WELDED CONNECTIONS
(I) Since the process does not involve driving holes,
the gross sectional area of the welding members is effective.
In the case of riveted tension member deductions have to be
made for the area lost due to punching holes.
(ii) Welded structures are comparatively lighter than
corresponding riveted structure.
(iii) A welded joint has a great strength. Often a welded
joint has the strength of the parent metal itself.
(iv) Repairs and further new connections can be done more
easily than in riveting.
(v) Welded joints provide rigidity. Hence welded members for
the same loading, are n smaller bending moments than
corresponding riveted members.
vi) Often welded joints are economical to riveted joints. For
a welded structure maintenance and painting costs are lesser
than for the riveted structure.
( Vii) Members of such shapes that afford difﬁculty for
riveting can be more easily welded.
(viii) A welded structure has a better ﬁnish and appearance
than the corresponding riveted structure
(ix) Connecting angles, gusset, plates, splicing plates can
be minimized and in many cases, can be avoided in welded
(x) Steel bars in reinforced concrete structures may be
welded easily. Lapping of bars may be avoided if welding is
(X!) It is possible to weld at any point at any part of a
structure. But riveting will always require enough
(xii) The process of welding does not involve great noise
compared to the noise produced in the riveting process.
DISADVANTAGES 0F WELDED CONNECTIONS
(1) Welding requires skilled labour and supervision.
(ii) Testing a welded joint is difﬁcult. An X-ray examination
alone can enable us to study the quality of the connection.
(iii) Due to uneven heating and cooling, the welded members
are likely to get warped at the welded surfaces.
(iv) Internal stresses in the weldedzones are likely to be