Electron-Probe Microanalysis: Some Revelations in the Investigation of Defects in Steel Products

Abstract

The unique imaging and microanalytical capability of the electron-probe microanalyser (EPMA) has been exploited in conjunction with light microscopy for exploring the genesis of some defects, which are detrimental to steel product quality. Investigations of surface and internal defects have revealed that defects in the finished steel product are often inherited at upstream stages and accentuated in the later stages of steel processing. While the occurrence of surface defects such as “slivers” in hot-rolled sheets and “linear cracks” in hot-rolled rounds has been largely attributed to subsurface non-metallic inclusions and slag/casting powder entrapment, microprobe analysis of internal defects such as “centre-line cracking” of thick plates have revealed the deleterious role of C and Mn macrosegration inherited during the continuous casting of steel slabs. The paper elucidates some of these findings, as unravelled by both qualitative and quantitative microprobe analysis.