FRACTURE-BEHAVIOR OF C-MN STEEL AND WELD METAL IN NOTCHED AND PRECRACKED SPECIMENS .1. FRACTURE-BEHAVIOR

In this investigation, fracture loads, toughness values, and the lengths of fibrous cracks on fracture surfaces were measured in Charpy V, crack tip opening displacement (COD), and precracked impact testing at various temperatures for C-Mn base steel and C-Mn and Ti-B weld metals. The uniaxial tensile properties of these metals were measured as well. By plotting the parameters related to toughness against the length of fibrous cracks measured, the energy absorbed by unit crack extension was estimated. The local cleavage fracture stresses, oy, were measured in Charpy V-notched and COD precracked specimens. The results showed σf about 600 MPa higher in the latter than in the former. Based on the results obtained, the factors controlling the toughness were analyzed. This was explained by the brittle transition temperature of the base metal being higher than that of the weld metal in the Charpy V test; however, it was lower in the COD test. The differences in fracture behavior between various types of toughness specimens were analyzed. The prerequisite condition for establishing the correlation between the results of Charpy V and COD tests was also discussed. © 1990 The Minerals, Metals & Materials Society - ASM International - The Materials Information Society.