Welded connection compared with the rivets, bolts, has the following advantages:

1) No drilling, saving time and labor;

2) The components of any shape can be directly connected, connected easily;

 3) The air tightness, water tightness is good, the structure stiffness, overall good.

Disadvantages : 1) near the weld heat affected zone, brittle material;

2) The welding residual stress to the structure susceptible to brittle fracture, residual deformation of the structure, shape, size change;

 3) Upon occurrence of welding cracks, it is easy to expand Common welding defects: cracks, porosity, incomplete penetration, slag inclusion, undercut, burn, pit, collapse, not full welded.

 the form of welding

(1) The relative position of the two sub-weldment: flush, lap, top pick

 (2) butt weld seam at the direction of force and points

a) Longitudinal: force direction and the weld direction orthogonal

 b) Inclined Slot: force direction and the direction of bias seam

 (3) angle of the weld seam at the direction of the force points:

a ) side seam: the length of the force perpendicular to the direction of the weld

b) side of the seam: the length of the force parallel to the direction of the weld

(4) Press the seam continuity

a) continuous welds: a better force

b) intermittent welds: prone to stress concentration

(5) according to the construction location: overlooking the welding, vertical welding, horizontal welding, Yang welding, construction welding position in which to look down the best, so the weld quality is the best, the worst overhead position welding.