The Mechanisms by Which Splitting Occurs Along Sheared Edges and in Charpy Specimens of a 12% Chromium Steel
1988; Taylor & Francis; Volume: 27; Issue: 1 Linguagem: Inglês
10.1179/cmq.1988.27.1.49
ISSN1879-1395
Autores Tópico(s)High-Velocity Impact and Material Behavior
ResumoA study was made of the delamination or splitting behaviour in transverse Charpy specimens and along the sheared edges of 12-mm plate specimens of a low carbon titanium-stabilized 12% chromium steel (designated 3CR12).It was found that planar-oriented splits, parallel to the rolling plane, which occur during transverse impact tests and shearing, result in a decrease in the impact shelf energy as well as in the ductile-to-brittle transition temperature. The degree of planar splitting is controlled mainly by the degree of mechanical anisotropy, which is related to the dimensional anisotropy of the grain structure. It is shown that splitting cannot be attributed to microstructural features alone; it is governed by different mechanisms that depend upon both the microstructure and the stress distribution at the crack tip. Splitting at sheared edges, which are subject to intense shear deformation, are nucleated by planar-oriented inclusions. Splitting in Charpy specimens was found to occur by transgranular cleavage, as well as by decohesion of ferrite-ferrite and ferrite-martensite grain boundaries, and was not related to the presence of inclusions in the microstructure. The excellent transverse toughness of 3CR12 steel is due to its fine-grained microstructure and the fact that splitting precedes transverse fracturing.Although a relatively high through-thickness tensile ductility was obtained for 12-mm 3CR12 plate, It is concluded that 12-mm 3CR12 plate could be susceptible to lamellar tearing in highly restrained welded joints.
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