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Nick-Break  Test

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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. Nick-Break  Test 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. Impact Test 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. 7-40



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