40 4.
Corner Fillet Joint (Fig. 19d) The
outside single fillet-welded corner joint is useful in many applications. The
strength of the joint can be increased
by adding a second fillet at the interior angle of the joint to form a double
fillet-welded corner joint. The
corner fillet joint may have the advantage of requiring no additional backing
other than that provided by the
structure itself. Note that the butting surfaces must be clean, dry, and tightly
fitted. 5. Corner
Joints with Backing (Fig. 19e) Either
square groove or single vee preparation can be used with backing to provide complete
penetration by welding
from one side of the joint. The requirements of this method are essentially the
same as for butt joint welds
with backing. (See Page 9). Plug
Weld Joint (Fig. 20) A
plug weld is used to join two pieces by welding through a hole in one of them
to secure a bond and fill the hole
with weld metal. It is important that the hole be large enough to prevent arcing
between the electrode and
the upper member. Unless the hole is beveled or tapered, the diameter of the hole
should be no less than
the thickness of the upper member. If sufficient welding current can be used and
excess weld metal above
the surface can be tolerated, weld penetration through the upper member can be
obtained without the
hole. This is only practical, however, for attaching a relatively thin member.
The size of the hole that can be used
for a completely fused plug weld made without changing electrode
position during welding will be determined
by the current that can be applied. A large hole may require
motion of the electrode during welding
to assure complete root fusion.
