THE FRACTOGRAPHY OF A HOT-ROLLED 3% Si-Fe SHEET STEEL AND ITS DUCTILE-BRITTLE TRANSITION TEMPERATURE RANGE
Luo Yang;Lu Chic-hun
Cite this article:
Luo Yang;Lu Chic-hun. THE FRACTOGRAPHY OF A HOT-ROLLED 3% Si-Fe SHEET STEEL AND ITS DUCTILE-BRITTLE TRANSITION TEMPERATURE RANGE. Acta Metall Sin, 1977, 13(3): 194-253.
Abstract The impact-toughness of a hot-rolled 3％ Si-Fe sheet steel has been measured to in-vestigate its ductile-brittle transition behavior. It was found that the transition from brit-tle to ductile fracture for this steel was within the temperature range of 0 to 100℃.At this range, the impact-toughness value was very sensitive to temperature changes,variation amounted to more than one order in magnitude could happen. Beyond thisrange, however, the curve rised asymptotically to a constant value, at which tempera-ture the sheet steel became ductile. In view of this, preheating the sheet to 60-80℃prior to cold-rolling was found to be an effective way in preventing brittle-cracking,whereas any aging effect which might deteriorate the magnetic properties of the sheetwas found to be neghglble. It is convenient to define the type of deformation after the indices of crystallineplanes being pre-determined by the etch-figure method. Fractography observations bySEM showed that, the {100} planes constituted the majority of the cleavage facets onbrittle fracture, but the narrow transition zone between the different cleavage facetsappeared to be {110} planes. Traces of {110) slip planes on cleavage facets mightoften be found on the cleavage facets, with the main cleavage direction almost parallel tothese slip traces. The majority of larger cleavage steps on the cleavage facets belongedto the {110} planes. During Plastic cracking many high-index crystalline planes otherthan {110) may be observed on the fracture surface, but cleavage along the {100}planes may still occur although with much less frequencies.
