WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 2
2 Free Bend Test.
a The free bend test has been devised to measure the
ductility of the weld metal deposited in a weld joint.
A test
specimen is machined from the welded plate with the weld located
in the center as shown in figure 46, view A, on the following
page. Each lengthwise edge of the specimen should be rounded off
to a radius not to exceed one-tenth of the thickness of the
specimen.
Any tool marks should be made lengthwise of the
specimen. And two lines, opposite each other, are scribed on the
face of the weld at a distance of 1/16 inch inward from the edges
of the weld as shown in figure 46, view B. The distance between
these two lines is measured in inches and recorded as the initial
distance X. The ends of the specimen are then bent to form two
30 degree angles at approximately one-third of the length inward
from the ends. The weld is thus centrally located to ensure that
all bending occurs in the weld.
b The bent specimen is then placed in a hydraulic or
mechanical machine as shown in figure 46, view C, and bent until
a crack greater than 1/16 inch appears on the face of the weld.
If no cracks appear on thin armor plate, continue bending until
the specimen can be bent in a vise. Heavier plate specimens are
usually tested in a hydraulic press or bending jig.
To prevent
slipping of the specimen, a groove should be machined in the
upper and lower contact plates of the bending equipment, as shown
in figure 46, view E.
c After being bent to the specifications prescribed in the
preceding subparagraph, the distance between the scribed lines is
again measured and recorded as the distance Y.
Find the
percentage of elongation by using the formula shown in figure 46.
The tested specimen must have a minimum elongation of 15 percent
with no cracks greater than 1/16 inch at the weld to pass this
test.
3 Nick Break Test.
a The nick break test has been devised to determine if the
weld metal of a welded butt joint has any internal defects, such
as slag inclusions, gas pockets, poor fusion, and/or oxidized or
burnt metal.
The specimen is obtained from a welded butt joint
either by machining or by cutting with an
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