Observations on the Plastic Deformation and Cracks in White Cast-Iron. (Studies on Alloy White Cast-Iron (5th Report))

Abstract

The author observed the deformation in various specimens of C 2∼4% white cast-iron and of C 3%, Ni 3.5∼4.5%, Cr 1∼2% alloy white cast-iron, as cast and heat-treated, subjected to bending, compression, hardness, and hammering tests. The results were summarized as follows: (1) When subjected to tensile stress cleavage cracks appeared mainly in the eutectic cementite, and passed through the primary crystals or along the boundaries. (2) When subjected to compression stress, he specimens, having low hardness values were broken along the glide plane 45° to the compressed axes and, near the glide fracture planes, the net-works of eutectic cementite were crushed, but the crushed cementite particles were enveloped by the flow of primary pearlitic crystals. Thus, overall fractures could not easily happen. (3) Slip lines were seen in the eutectic cementite in the compression, hardness and hammering test pieces. The slip lines in the eutectic cementite for chilled specimens were about parallel to the chiller surfaces. (4) Hair cracks often appeared in the eutectic cementite and sometimes in or along the needle-like proeutectoid cementite or the martensite plates. Tempered graphite and Mn-S particles seemd to have no relation to the cracks.