deposit. The result of a pass is a weld bead.) The
sequences we will consider next consist of
multiple-pass layer welds.
A LAYER consists of two or more weld beads.
Figure 7-17 shows the use of multiple passes and
layers in making a groove weld. The number of
layers required to complete the weld is determined
by the thickness of the metal being welded and the
diameter of the welding rod being used.
Figure 7-17.--Multiple-pass layers.
Figure 7-18 illustrates block sequence, buildup
sequence, and cascade sequence. Note that all of
increment itself are left along the joint. Once the
these sequences involve longitudinal sequence and
length of the joint has been welded in this manner,
m u l t i p l e passes and layers. The BLOCK
the welder fills the gaps, thus producing a
SEQUENCE, shown in view A of figure 7-18, is a
continuous weld. The order in which the parts of
longitudinal sequence having a specified buildup
the weld are made may differ from that indicated in
order. Individual sections or blocks of the
view B of figure 7-16. Another order, such as
6-7-5-3-l-4-2, might be equally satisfactory. For this
continuous joint are partially or completely welded
reason, the wandering sequence is often called the
in an order somewhat like that of a backstep or
random or skip sequence. No matter which order
wandering sequence before intervening sections are
deposited. The term BUILDUP SEQUENCE
is selected, the pattern must be predetermined.
refers to the order in which the weld beads of a
Increment length is determined in the way described
for the backstep sequence. It is a good idea to lay
multiple-pass weld are deposited with respect to the
out the joint increment lengths and number each
cross section of the joint. Thus, a buildup sequence
portion according to the chronological order in
is a part of any joint that requires layers of filler
which it is to be welded.
metal deposits to make the weld. View B of figure
7-18 shows a buildup sequence. The CASCADE
Thus far, we have considered only those
SEQUENCE, shown in view C of figure 7-18, is a
sequences in which a single pass or weld bead is
variation of the block sequence. It has a specified
involved. (A PASS is a single progression of a
buildup order, but the weld beads are deposited in
welding operation along a joint or weld increment
Figure 7-18.--Block, buildup, and cascade sequences.