The Effect of Elongated Sulfide Inclusions on Ductility and Ductile Fracture of a Structural Steel
Transactions of the Iron and Steel Institute of Japan
S ynopsis Uniaxial lensile ductility and duclile fracture of a commercially melled and laboratory rolled structural steel were investigated with a special emphasis on elongated sulfide inclusions by optical microscopy and eleclron microfractography . i n the course of plastic deformation, extensive cracks develop from cracking of sulfide and decohesion of sulfide-matrix interface. These cracks grow to a size comparable to that of sulfide inclusions themselves . T he final fracture occurs
... cture occurs /;reslllnably by the /lrocess of coalescence of microvoids, this being inJerred from lhe existence of elongated dimples. Elongated sulfide inclusions are understood to impose geometrical conditions 10 accelerate such process. Premature decohesion of sulfide-matrix interface is the governing mechanism in loading in thickness direction. This type of fracture becomes im/Jortant when loading direction deviates from the rolling direction. Lowered rolling temperatllre elongates sulfide alld weakens cohesive strenglh q! sulfide-matrix interface and decreases dllctility in thicklless direclion. It a/50 causes microjissllrillg in CharlJY impact lesl.