This test is used extensively to investigate the fracture characteristics of ferritic steels 15.9 mm (5/8 in.) and thicker. A crack-starter bead of hard surfacing material is deposited on the specimen to be tested, then a notch is cut into the bead. After cooling to a specified temperature, the specimen is placed on an anvil, with the crack-starter bead down. A weight is dropped on the specimen from a height selected to give the necessary
impact energy. The impact energy is determined by the approximate yield strength of the weld metal being tested.
When the weight strikes the specimen, it either bends until it hits a deflection stop, or cracks in two pieces, with little or no bending.
The drop-weight test is also used to determine the nil-ductility transition temperature of the weld metal. This test is conducted by impacting a series of specimens, each tested at a different temperature. The maximum temperature at which a specimen breaks is the nil-ductility transition. This temperature must be determined within 5°C (10°F). Details of the Drop Weight Test are published in ASTM Standard E208.