Electron-probe microanalysis: Some applications in the assessment of steelproduct quality

Electron-probe microanalysis was employed concurrently with optical metallo graphy to understand the genesis of surface and internal defects which are critical to steel product quality. Investigations of surface defects such a s 'slivers' on hot-rolled sheets, 'edge-cracking' of hot-rolled coils and l ongitudinal surface cracking of rolled round bars revealed that such defect s in finished products are often inherited from upstream processing stages and eventually accentuated in the final stages of processing. Inadequately deoxidized steel with a high gas content, improper casting practices, usage of inferior quality mould powder and bad reheating practice in respect of temperature and furnace atmosphere were found to impair synergistically the quality of finish products. Microprobe analysis of internal defects such a s cracks in billets and axial discontinuities/cracks in thick steel plates produced from continuously cast slabs elucidated the role of specific macro segregation-causing elements during continuous casting and their ultimate e ffect in inducing transformation to undesirable microstructures which enhan ce cracking propensity. Some of these metallurgical applications where micr oprobe analysis, both qualitative and quantitative, has been used for the e valuation of steel product quality are described. Copyright (C) 1999 John W iley & Sons, Ltd.