Figure 7-65.Nick-break test of a butt weld.
testing laboratories for the daily testing of specimens.
Simple in construction and easy to use, it works by
hydraulic pressure and can apply a direct load up to
40,000 pounds, and even more on small specimens.
When you make the test, position the specimen in the
machine as previously indicated and start pumping the
actuator. Keep your eye on the large gauge and watch
the load increase. You will know the actual load under
which the test piece bends by the position of an auxiliary
hand that is carried along by the gauge pointer. The hand
remains at the point of maximum load after the pointer
returns to zero.
The NICK-BREAK TEST is useful for determining
the internal quality of the weld metal. This test reveals
various internal defects (if present), such as slag inclu-
sions, gas pockets, lack of fusion, and oxidized or
burned metal. To accomplish the nick-break test for
checking a butt weld, you must first flame-cut the test
specimens from a sample weld (fig. 7-65). Make a saw
cut at each edge through the center of the weld. The
depth of cut should be about 1/4 inch.
Next, place the saw-nicked specimen on two steel
supports, as shown in figure 7-65. Using a heave ham-
mer, break the specimen by striking it in the zone where
you made the saw cuts. The weld metal exposed in the
break should be completely fused, free from slag inclu-
sions, and contain no gas pockets greater than 1/16 inch
across their greatest dimension. There should not be
more than six pores or gas pockets per square inch of
exposed broken surface of the weld.
You use the IMPACT TEST to check the ability
of a weld to absorb energy under impact without
Figure 7-66.Test pieces for impact testing.